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Oestrous Cycle Pharmacological Manipulation - Anatomy & Physiology

2013-12-19T07:38:43Z

Vulpesferrilata: /* Light */

= Introduction =

The manipulation of normal cyclic activity ensures optimum production or is convenient for the herdsmen or owner. In the case of seasonal breeders, it allows them to breed out of season, or to advance the onset of cyclic activity. There are also advantages in ensuring all animals in a group come into oestrus at the same time for ease of management.
There are two methods of oestrus synchronisation. One is physiological manipulation of the oestrous cycle, and the other pharmacological manipulation of the cycle. Various factors must be considered before deciding which method to use. These factors will be specific to the type of production unit and species, also the stage of the natural oestrous cycle in the animal/herd involved.

= Factors Influencing Reproduction =

== Physiological ==

=== Light ===

* Cyclic activity in the mare, ewe, goat and cat depend on changes in the number of daylight hours.
* Tungsten and fluorescent lamps can be used to artificially manipulate the photoperiod.
* Mare and queen are stimulated by increasing day length (long day breeders)
** If mares are stabled in December and exposed to artificial light for increasing duration, the onset of oestrous cyclicity and ovulation will be advanced.
* Ewe and goat are stimulated by decreasing day length (short day breeders)
** Providing ewes with controlled light housing enables change in the breeding season from autumn and winter to spring and summer.
** If there is no change in duration of light stimulus, it is possible to make ewes cycle all year round.

=== Nutrition ===

* Improved nutrition prior to mating (flushing) will increase the number of follicles which mature and ovulate.
* Used in the ewe and sow successfully.

=== Other Methods ===

* The presence of a male can stimulate the onset of cyclic activity in some species (see 'Ram Effect' for more detail).
* In sows and gilts, removing piglets will cause a more rapid return to cyclic activity post-partum.
* If litters are weaned from a group of sows at the same time, there will also be some synchronisation of oestrus.
* Also in gilts and sows, the stress of changing environment or transport stress can stimulate the onset of oestrus post-partum.

== Pharmacalogical ==

=== Preparations which Stimulate Release of Anterior Pituitary Hormones ===

* Ovarian steroids, particularly oestrogens, exert a positive-feedback on the anterior pituitary gland and hypothalamus.
* Oestrogens and synthetic oestrogens are used to stimulate oestrus.
* They have a direct effect on stimulating oestrus behaviour and changes in the genital tract.
* They may also stimulate release of pituitary gonadotrophins.
* Synthetic GnRH can be used to stimulate the release of endogenous gonadotrophins.

=== Preparations which Supplement or Replace Pituitary Gonadotrophins ===

* Purified LH and FSH can be extracted from the pituitary gland in the abbatoir, but this is too time consuming to be practiced commercially. There is also the risk of transmitting diseases such as BSE.
* Instead, two substitutes are used commercially:
** Equine Chorionic Gonadotrophin (eCG): obtained from the serum of pregnant mares. This has an 'FSH-like' effect, but with some 'LH-like' activity.
** Human Chorionic Gonadotrophin (hCG): obtained from the urine of pregnant women. It has mainly an 'LH-like' effect, but with some 'FSH-like' activity.

=== Oestrogens ===

* Used to induce oestrus in anoestrous animals.
* Have a direct effect on oestrus behaviour and the genital tract.
* May inhibit the pituitary release of gonadotrophins in high doses.
* Do not initiate ovarian activity or ovulation.

=== Progestogens ===

* Progesterone and its synthetic analogues are used extensively in most domestic species to synchronize oestrus.
* Exogenous progestogens act in the same way as the corpus luteum, resulting in a negative feedback effect on the anterior pituitary gland.
* This in turn results in supression of gonadotrophin release, so cyclic activity ceases.
* When the progestogen is withdrawn, the negative feedback block on the anterior pituitary gland is removed. This initiates a retun to cyclic activity.

=== Prostaglandins ===

* The length of the interoestrus interval in most domestic species is controlled by the duration of the lifespan of the corpus luteum.
* Administration of PGF2α or its analogues will cause premature luteolysis of the corpus luteum.
* This can be used to manipulate the normal pattern of cyclic activity.
* Prostaglandins will induce luteal regression. As a result, progesterone levels fall and negative feedback on the anterior pituitary gland is removed. Subsequently, levels of gonadotrophins begin to rise, leading to increased follicular growth under the influence of FSH. Oestradiol production begins to rise as follicles become dominant. When oestradiol rises above the threshold, it feeds back positively at the level of the hypothalamus. The hypothalamus then releases a surge of GnRH. This then stimulates the anterior pituitary gland to release a surge of LH which is responsible for ovulation.
* The corpora lutea of the cow, mare, sow, ewe and goat respond to administration of exogenous prostaglandins.
* In the cow, mare, ewe and goat the new developing corpus luteum is refractory to prostaglandins for 3-5 days after ovulation.
* At the end of the cycle, the corpus luteum is unaffected by exogenous prostaglandin because it is already regressing under the influence of its own endogenous luteolytic hormones.
* The corpus luteum is resonsive for:
** Cow: 13 days
** Goat: 13 days
** Mare: 10 days
** Ewe: 9 days
* In the sow, the corpus luteum is refractory for up to 11 days after ovulation. It is only resposive for a period of 7-8 days.
* In the bitch and queen, corpora lutea are unresponsive to exogenous prostaglandins unless they are given repeated doses.
* Prostaglandins will cause abortion, do not use in animals that might be pregnant!

=== Melatonin ===

* The pineal gland controls reproductive cyclicity in seasonal breeders (sheep, goats, horses and cats) by the secretion of melatonin as the daylight hours are reduced. For more information on this mechanism, click [[Seasonality_of_Reproduction_- Anatomy & Physiology#Mechanism_of_seasonality|here]]
* Melatonin can be used successfully to modify seasonal activity in the species mentioned, most practically the ewe.

= Manipulation of the Oestrous Cycle in Various Species =

== Ewe ==

True synchronization in the ewe is not achieved even with the combined use of prostaglandins and progestogens with much time and effort under controlled conditions of a lab setting. Thus, in practice these methods are never completely effective for the ewe.

=== Factors to Consider Before Deciding which Method to Use ===

* Degree of synchronization required
* The season
* Economic and market factors
* Physiological manipulation is usually cheaper, but it does not result in tight synchronization and can only be used under certain conditions.
* Pharmacological methods tend to give tight synchronization throughout the year, but are more expensive in terms of both drugs and labour.

=== Physiological: The Ram Effect ===

* Ram stimulate gonadotrophin secretion form the anterior pituitary gland and subsequent ovulation in anoestrus ewes through chemosensory cues.
* Isolate ewes for 3-4 weeks before introducing the ram.
* Only effective at certain times of the year - just before commencement of the natural breeding season. This method is not effective for ewes in deep anoestrus.
* The majority of ewes ovulate within 6 days of introducing the ram.
* Priming with progesterone (intravaginal sponge or intramuscular injection) prior to the introduction of the ram will increase the percentage of ewes showing oestrus behaviour.
* Cheap and easy, but not very effective as a sole method.

=== Pharmacological: Gonadotrophins ===

* Use of eCG alone to induce oestrus in anoestrus ewes is not very successful.
* Administration of progesterone before the injection of eCG causes synchronised oestrus and ovulation in seasonally anoestrus ewes.

=== Pharmacological: Progestogens ===

* Used alone or in conjunction with other hormones.
* Used to induce oestrus in the anoestrus ewe during the non-breeding season and for oestrus synchronization in cyclic ewes.
* To be effective, treatment must last for the length of the normal luteal phase (12-14 days).
* In the anoestrus ewe, progesterone withdrawal is complemented by follicle stimulating treatments such as eCG. This will stimulate oestradiol secretion due to its 'FSH-like' effect.
* Progestogens are now used more commonly than progesterone itself, because progesterone has a short-half life. These include:
** Fluorogestone acetate (FGA)
** Medroxyprogesterone acetate (MAP)

==== Intravaginal Sponges ====

* The sponge is impregnated with progestogens and inserted into the vagina.
* Progestogen is absorbed in sufficient quantities to cause a negative feedback effect on pituitary function.
* When used outside of the normal breeding season, eCG is administered at the end of the progestogen priming period.
* Fertility may be reduced at first mating after synchronized oestrus. This may be due to poor absorbtion of progestogen from the sponge. It may also be the effect of abnormal hormone levels on sperm survival.

=== Pharmacological: Prostaglandins ===

* Used to induce luteal regression and subsequent cyclicity in cyclic ewes.
* Administration of PGF2α or its analogues during the period when there is a sensitive corpus luteum present induces oestrus 36-46 hours after injection.
* Ovulation will then occur shortly afterwards.
* In order to synchronize a group of ewes in randomly different stages of the oestrous cycle, two injections are required 8-9 days apart in order to ensure administration at a time when there is a sensitive corpus luteum present in all animals of the group.
* Uses are limited for a number of reasons:
** Having to give two injections is impractical under field conditions
** The induced oestrus leads to poor fertility, probably due to the limited exposure of the tract to progesterone.
** Prostaglandins can only be used in cyclic animals, not in seasonal anoestrus.
* It is usually only used in combination with progestogens.

=== Pharmacological: Melatonin ===

* Used comercially to advance the onset of the breeding season.
* The breeding season can be advanced by 2-3 months with good fertility.
* Administered as an implant containing 18mg of melatonin, which is inserted subcutaneously at the base of the ear.
* Ewes should be completely isolated from rams at least 7 days before insertion of the implant.
* They should remain separated for at least 30 days, and no more than 40 days.
* Rams should then be reintroduced.
* Peak mating activity occurs 25-35 days later.
* However, this is much work for little benefit because it cannot be used for ewes in deep anoestrus.

=== Immunization ===

* Use of an immunogen, produced by conjugating a derivative of adrostenedione with human serum albumin, increases lambing rates.
* When injected, it stimulates the production of antibodies to androstenedione.
* The antibodies bind free androstendione in the blood.
* This results in an increase in the number of lambs born, although the precise reason for this is unknown.
* Inject twice:
** 8 weeks before tupping
** 4 weeks before tupping
* If ewes have been treated in the previous season, only one injection is required at 4 weeks before tupping.
* Only inject ewes which are to be fed adequately during pregnancy, due to the dangers of pregnancy toxaemia.
* Immunization against inhibin will soon be available for commercial use.
** This will reduce the inhibitory effect of inhibin on FSH secretion from the anterior pituitary gland.
** The subsequent increase in FSH will lead to an increase in the nuber of developing follicles, thus better lambing rates.

== Cow ==

=== Controlling Oestrous ===

* The main reasons for controlling oestrus are:
** Induction of oestrus in dairy cows that are not observed in oestrus by 45 days post-partum.
** Synchronization of groups of heifers for insemination with semen of 'easy calving' bulls.
** Reducuction in the time necessary for oestrus detection.
** To facillitate the use of artificial insemination.
** Synchronization of donor and recipient cows for embryo transfer.
** Induction of ovarian activity in beef cows with lactational anoestrus.

=== Pharmacological: Gonadotrophins ===

* eCG can be used to stimulate follicular growth and ovulation in the anoestrus cow.
* Dose response is variable and can result in multiple ovulations.
* Withold insemination at the induced oestrus.
* The cow often returns to anoestrus, so overall the use of eCH is not recommended.

=== Pharmacological: Prostaglandins ===

* Used to synchronize oestrus in groups of cows and heifers. Oestrus detection is difficult in this species, so this is advantageous for optimum timing of artificial insemination.
* Give two injections of PGF2α or an analogue such as cloprostenol at an interval of 11 days to a group of cows/heifers all at different stages of the oestrous cycle.
* 3-5 days after the second injection, all animals treated will come into oestrus and ovulate at about the same time.
* If only a single injection is given, conception rates are lower after subsequent artificial insemination.
* Two injections are required in order to ensure the prostaglandins are administered to all animals in a period where the corpus luteum is sensitive.
* To reduce cost and improve pregnancy rates, the following regime is used:
** All animals are injected with PGF2α on the same day and observed for oestrus during the following 5 days.
* The length of time between the injection and onset of oestrus does vary slightly, depending on the ovarian status at the time of the injection. If there is a large, dominant follicle, the time until oestrus onset will be short, whereas if only small follicles are present, the period will be longer.
* Lactating dairy cows have a more variable interval between the injection and onset of oestrus.
** Any identified in oestrus are inseminated
** Any not identified as being in oestrus receive a second injection of prostaglandin followed by artificial insemination.
** Any animals that exhibit oestrus following the first insemination are reinseminated.

=== Pharmacological: Progestogens ===

* Used to synchronize groups of cows and heifers for artificial insemination and to overcome problems with oestrus detection.
* Treatment of random cycling animals for 18-21 days results in synchronization of oestrus.
* When the treatment ceases, oestrus occurs in 4-6 days.
* Fertility at first oestrus is lower, due to impaired sperm transort as a result of the atypical hormone balance after treatment is withdrawn.
* To ensure the natural corpus luteum of the cycle has regressed by the time of progestogen withdrawal, progestogen treatment is often combined with a luteolytic factor:
** Oestradiol at the start of treatment or prostaglandin analogues at the end of treatment.
** Oestradiol is best because as well as inducing luteal regression, it affects follicular dynamics so improves fertility at first oestrus.
* In non-cyclic cows, progestogens sensitize the hypothalamic-anterior pituitary-gonadal axis. This approach can be used in cattle with innactive ovaries.
* Injecting with eCG at progestogen removal stimulates follicular maturation and ovulation.
* Oestrus and ovulation after treatment with progestogens occurs earlier and with more precise timing than following injection of prostaglandin alone.

==== Progesterone Releasing Intravaginal Device (PRID) ====

* Stainless steel coil covered with an inert elastomer incorporating 1.55g of progesterone.
* Placed in the vagina using a speculum.
* Whilst in place, progesterone is absorbed to produce plasma concentrations that mimic maximum levels at dioestrus.
* When removed after 12 days, the cow will come into oestrus in 2-3 days.
* Some may also contain Oestradiol Benzoate.
* Oestradiol Benzoate is anti-luteotrophic and mildly luteolytic.
* Almost 100% synchronization can be achieved if an injection of PGF2α is administered 24 hours before removing the device. This has a far greater luteolytic effect than Oestradiol Benzoate alone.
* Can be used in cyclic cows to synchronize oestrus, best inserted on day 13-14.
* Can be used in anoestrus dairy and beef cows to induce oestrus.

==== Controlled Internal Drug Release Device (CIDR) ====

* A hinged T-shaped device impregnated with progesterone.
* Placed in the vagina using a speculum.
* Whilst in place, progesterone is absorbed to produce plasma concentrations that mimic maximum levels at dioestrus.
* When removed after 12 days, the cow will come into oestrus in 2-3 days.
* Can be used in cyclic cows to synchronize oestrus, best inserted on day 13-14.
* Can be used in anoestrus dairy and beef cows to induce oestrus.

== Mare ==

=== Reasons to Control the Oestrous Cycle ===

* Better planning in studs
* Synchronizing the donor and recipient for embryo transfer.
* In racehorses, performance of 2-year olds is important. The age of a horse is measured from 1st January, so it is important that foals are born as soon as possible after 1st January in order to produce the oldest '2 year old' possible.

=== Control in the Transition Period ===

* Day length is an important stimulus for cyclicity.
* Aim is to simulate the natural photoperiod that would occur later on in the year.
* Exposure to ~116 hours of daylight in mid-November can advance the first ovulation from early April to early February.
* Combining photoperiod manipulation with GnRH achieved optimal results.

=== Control in the Breeding Period ===

* During the natural breeding period, manipulation is mainly carried out to treat fertility disorders.
** Prolonged oestrus can be treated with a Progesterone Rleasing Intravaginal Device (PRID)
** A persistent corpus luteum can be treated with prostaglandins.
* Other reasons for manipulation include:
** Shortening anoestrus after foaling
** Synchronizing oestrus in a group of mares

===== Pharmacological: Progestogens =====

* In competition horses, it is desirable to prevent the mare from coming into oestrus at inopportune times.
* In some cases it is desirable to synchronize a group of animals.
* A daily injection of progesterone (0.3mg/Kg) will prevent oestrus.
* The mare will return to oestrus 3-7 days after treatment ceases.
* Oral progestoges recommended include:
** Allytrenbolone
** Altrenogest
* These can be used in a number of ways:
1. '''To stimulate the onset of cyclic activity'''
* Administer 0.044mg/Kg mixed in with the feed for 10 days and then stop.
* Give in the late transition period from anoestrus to cyclic activity when follicles are present.
* Better results when combined with increased lighting.
2. '''To suppress oestrus for an event'''
* Feed for 15 days at 0.044mg/Kg
3. '''To suppress oestrus in mares with prolonged oestrus'''
4. '''To control the time of oestrus for effective use of the stallion'''
* Feed for 15 days, then stop.
* Mare should come into oestrus 2-3 days later.

===== Pharmacological: Prostaglandins =====

* Eliminates the need for frequent testing for oestrus. It is also useful if a heat is missed, particularly the 'foal heat'.
* PGF2α and the synthetic analogue clonprostenol are used.
* Onset of oestrus is well synchronized 3 days after treatment.
* Subsequent ovulation occurs 7-12 days after treatment.
* Injecting hCG or GnRH on day 2-3 of the induced oestrus achieves the best results.

=== Inducing Ovulation ===

* The main method is the use of hCG
* In the presence of a follicle >2.5 cm, hCG will induce ovulation 24-48 (on average 35) hours after administration.

== Sow ==

=== Pharmacological: Progestagens ===

* Used to synchronize cyclic gilts and sows
* Difficult to treat group-fed animals, since it is contraindicated for pregnant animals and boars.
* Progestogens used are:
** Altrenogest
** Allytrenbolone
* Supress follicular maturation when fed daily at 15-20mg with no effect on the life span of corpora lutea.
* Feed for 18 days to achieve synchronization of oestrus 5-7 days after withdrawal.

=== Pharmacological: Prostaglandins ===

* Theoretically gives reliable synchronization of oestrus in groups of gilts and sows.
* Enables ease of artificial insemination and batch farrowing.
* But, prostaglandins and their analogues are not luteolytic until day 11-12 of the oestrous cycle.
* Thus, an injection regime for groups of animals at random periods of the oestrous cycle is not possible.
* However, it is possible after injection of oestrogen (see below)
* Another indication for use of prostaglandins is to induce luteolysis of accessory corpora lutea after use of eCG or hCG at any stage of the oestrous cycle.

=== Pharmacological: Oestrogens ===

* Prolong the lifespan of corpora lutea
* Inject oestrogen on day 10-14 of the oestrus cycle.
* Then, prostaglandins can be injected after 5-20 days.
* Oestrus will occur 4-6 days later.

=== Pharmacological: Gonadotrophins ===

* In anoestrus gilts and sows eCG, or a combination of eCG and hCG will promote follicular growth and oestrus.
* If this is followed by another injection of hCG 72 hours later, this will ensure ovulation occurs.
* This can also be used to synchronize cyclic activity, especially if used in combination with progestogen.

== Bitch ==

=== Pharmacological: Gonadotrophins ===

* Combinations of eCG and hCG can induce oestrus in the anoestrus bitch.
* Sometimes this is combined with oestrogens.
* However, conception rates after the induced ovulation tend to be poor.

=== Pharmacological: Synthetic Progestogens ===

* Used to suppress oestrus.
* Commonly used progestogens include:
** Megoestrol acetate
** Proligestone
** Medroxyprogesterone
* These are available orally or for injection.
* They can be used to postpone the onset of oestrus when administered during anoestrus.
** Can be postponed for up to a year by injecting progestogens at intervals of 3-5 months or giving a 40 day course of oral tablets twice a week.
* Another use is to prevent oestrus from occuring if administered at the fist signs of pro-oestrus.
** This is achieved by a single injection or oral progestogen at a higher dose rate than for postmonement, but for a shorter duration.
* Following administration of progestogens, the interval before onset of the next oestrus is unpredictable if treatment is not continued.
* Frequent use can predispose the bitch to reproductive disorders, particularly cystic glandular hyperplasia of the endometrium.
* First generation progestogens such as Medroxyprogesterone acetate (MPA) carry the risk of stimulating growth hormone (GH) secretion. This leads to an increased risk of acromegaly, mammary tumours and diabetes mellitus.

==== Proligestone (PRG) ====

* A new drug specifically designed to prevent oestrus in bitches and queens.
* It is particularly suitable because:
** Strongly anti-gonadotrophic
** Weakly progestagenic
** Antioestrogenic, so effectively controls vulval swelling and bleeding.

== Queen ==

Suppression of oestrus may be desireable for a number of reasons, but mostly to plan litters throughout the year and allow the queen a rest from sexual activity after a litter. This allows the queen to regain condition before being bred again. If the queen is allowed to call without mating, it may lead to loss in condition due to innapetance during oestrus.

=== Physiological ===

* Pseudopregnancy can be achieved by mating queens with a castrated Tom, or through stimulating coitus by swabbing the vagina.
* Pseudopregnant queens will not return to oestrus for 4-8 weeks.

=== Pharmacological: hCG ===

* Administration of hCG can be used to induce ovulation.
* This will cause pseudopregnancy.
* Pseudopregnant queens will not return to oestrus for 4-8 weeks.

=== Pharmacological: Androgens ===

* Androgen anabolic steroids used daily postpone calling.
* Give daily oral doses ~30 days before anticipated oestrus.
* Induces masculinization

=== Pharmacological: Progestogens ===

* Used to suppress oestrus
* Injectable forms include:
** Medroxyprogesterone acetate
*** Will suppress oestrus for 7 months or more following a single injection
*** Can be repeated every 5 months to achieve permanent oestrus suppression.
** Proligestone
* Oral progestogens are more flexible.
* The most commonly used oral progestogen is Megoestrol acetate.
** Used to prevent oestrus period by administering 5mg as soon as signs of oestrus are observed.
** Postponment is achieved by administering 2.5mg daily or weekly depending on whether the treatment is in the breeding season or the period of anoestrus.
* Side effects include lethargy and weight gain, there is also a predisposal to diabetes mellitus.

[[Category:Female Reproduction]][[Category:Pharmacology]]
[[Category:Bullet Points]]

Oestrous Cycle Pharmacological Manipulation - Anatomy & Physiology

2013-12-19T07:38:09Z

Vulpesferrilata: /* Light */

= Introduction =

The manipulation of normal cyclic activity ensures optimum production or is convenient for the herdsmen or owner. In the case of seasonal breeders, it allows them to breed out of season, or to advance the onset of cyclic activity. There are also advantages in ensuring all animals in a group come into oestrus at the same time for ease of management.
There are two methods of oestrus synchronisation. One is physiological manipulation of the oestrous cycle, and the other pharmacological manipulation of the cycle. Various factors must be considered before deciding which method to use. These factors will be specific to the type of production unit and species, also the stage of the natural oestrous cycle in the animal/herd involved.

= Factors Influencing Reproduction =

== Physiological ==

=== Light ===

* Cyclic activity in the mare, ewe, goat and cat depend on changes in the number of daylight hours.
* Tungsten and fluorescent lamps can be used to artificially manipulate the photoperiod.
* Mare and queen are stimulated by increasing day length (long day breeders)
** If mares are stabled in December and exposed to artificial light for increasing duration, the onset of oestrous cyclicity and ovulation will be advanced.
* Ewe and goat are stimulated by decreasing day length (short day breeders)
** Providing ewes with controlled light housing enables change in the breeding season from autumn and winter to spring and summer.
** If there is no change in duration of light stiulus, it is possible to make ewes cycle all year round.

=== Nutrition ===

* Improved nutrition prior to mating (flushing) will increase the number of follicles which mature and ovulate.
* Used in the ewe and sow successfully.

=== Other Methods ===

* The presence of a male can stimulate the onset of cyclic activity in some species (see 'Ram Effect' for more detail).
* In sows and gilts, removing piglets will cause a more rapid return to cyclic activity post-partum.
* If litters are weaned from a group of sows at the same time, there will also be some synchronisation of oestrus.
* Also in gilts and sows, the stress of changing environment or transport stress can stimulate the onset of oestrus post-partum.

== Pharmacalogical ==

=== Preparations which Stimulate Release of Anterior Pituitary Hormones ===

* Ovarian steroids, particularly oestrogens, exert a positive-feedback on the anterior pituitary gland and hypothalamus.
* Oestrogens and synthetic oestrogens are used to stimulate oestrus.
* They have a direct effect on stimulating oestrus behaviour and changes in the genital tract.
* They may also stimulate release of pituitary gonadotrophins.
* Synthetic GnRH can be used to stimulate the release of endogenous gonadotrophins.

=== Preparations which Supplement or Replace Pituitary Gonadotrophins ===

* Purified LH and FSH can be extracted from the pituitary gland in the abbatoir, but this is too time consuming to be practiced commercially. There is also the risk of transmitting diseases such as BSE.
* Instead, two substitutes are used commercially:
** Equine Chorionic Gonadotrophin (eCG): obtained from the serum of pregnant mares. This has an 'FSH-like' effect, but with some 'LH-like' activity.
** Human Chorionic Gonadotrophin (hCG): obtained from the urine of pregnant women. It has mainly an 'LH-like' effect, but with some 'FSH-like' activity.

=== Oestrogens ===

* Used to induce oestrus in anoestrous animals.
* Have a direct effect on oestrus behaviour and the genital tract.
* May inhibit the pituitary release of gonadotrophins in high doses.
* Do not initiate ovarian activity or ovulation.

=== Progestogens ===

* Progesterone and its synthetic analogues are used extensively in most domestic species to synchronize oestrus.
* Exogenous progestogens act in the same way as the corpus luteum, resulting in a negative feedback effect on the anterior pituitary gland.
* This in turn results in supression of gonadotrophin release, so cyclic activity ceases.
* When the progestogen is withdrawn, the negative feedback block on the anterior pituitary gland is removed. This initiates a retun to cyclic activity.

=== Prostaglandins ===

* The length of the interoestrus interval in most domestic species is controlled by the duration of the lifespan of the corpus luteum.
* Administration of PGF2α or its analogues will cause premature luteolysis of the corpus luteum.
* This can be used to manipulate the normal pattern of cyclic activity.
* Prostaglandins will induce luteal regression. As a result, progesterone levels fall and negative feedback on the anterior pituitary gland is removed. Subsequently, levels of gonadotrophins begin to rise, leading to increased follicular growth under the influence of FSH. Oestradiol production begins to rise as follicles become dominant. When oestradiol rises above the threshold, it feeds back positively at the level of the hypothalamus. The hypothalamus then releases a surge of GnRH. This then stimulates the anterior pituitary gland to release a surge of LH which is responsible for ovulation.
* The corpora lutea of the cow, mare, sow, ewe and goat respond to administration of exogenous prostaglandins.
* In the cow, mare, ewe and goat the new developing corpus luteum is refractory to prostaglandins for 3-5 days after ovulation.
* At the end of the cycle, the corpus luteum is unaffected by exogenous prostaglandin because it is already regressing under the influence of its own endogenous luteolytic hormones.
* The corpus luteum is resonsive for:
** Cow: 13 days
** Goat: 13 days
** Mare: 10 days
** Ewe: 9 days
* In the sow, the corpus luteum is refractory for up to 11 days after ovulation. It is only resposive for a period of 7-8 days.
* In the bitch and queen, corpora lutea are unresponsive to exogenous prostaglandins unless they are given repeated doses.
* Prostaglandins will cause abortion, do not use in animals that might be pregnant!

=== Melatonin ===

* The pineal gland controls reproductive cyclicity in seasonal breeders (sheep, goats, horses and cats) by the secretion of melatonin as the daylight hours are reduced. For more information on this mechanism, click [[Seasonality_of_Reproduction_- Anatomy & Physiology#Mechanism_of_seasonality|here]]
* Melatonin can be used successfully to modify seasonal activity in the species mentioned, most practically the ewe.

= Manipulation of the Oestrous Cycle in Various Species =

== Ewe ==

True synchronization in the ewe is not achieved even with the combined use of prostaglandins and progestogens with much time and effort under controlled conditions of a lab setting. Thus, in practice these methods are never completely effective for the ewe.

=== Factors to Consider Before Deciding which Method to Use ===

* Degree of synchronization required
* The season
* Economic and market factors
* Physiological manipulation is usually cheaper, but it does not result in tight synchronization and can only be used under certain conditions.
* Pharmacological methods tend to give tight synchronization throughout the year, but are more expensive in terms of both drugs and labour.

=== Physiological: The Ram Effect ===

* Ram stimulate gonadotrophin secretion form the anterior pituitary gland and subsequent ovulation in anoestrus ewes through chemosensory cues.
* Isolate ewes for 3-4 weeks before introducing the ram.
* Only effective at certain times of the year - just before commencement of the natural breeding season. This method is not effective for ewes in deep anoestrus.
* The majority of ewes ovulate within 6 days of introducing the ram.
* Priming with progesterone (intravaginal sponge or intramuscular injection) prior to the introduction of the ram will increase the percentage of ewes showing oestrus behaviour.
* Cheap and easy, but not very effective as a sole method.

=== Pharmacological: Gonadotrophins ===

* Use of eCG alone to induce oestrus in anoestrus ewes is not very successful.
* Administration of progesterone before the injection of eCG causes synchronised oestrus and ovulation in seasonally anoestrus ewes.

=== Pharmacological: Progestogens ===

* Used alone or in conjunction with other hormones.
* Used to induce oestrus in the anoestrus ewe during the non-breeding season and for oestrus synchronization in cyclic ewes.
* To be effective, treatment must last for the length of the normal luteal phase (12-14 days).
* In the anoestrus ewe, progesterone withdrawal is complemented by follicle stimulating treatments such as eCG. This will stimulate oestradiol secretion due to its 'FSH-like' effect.
* Progestogens are now used more commonly than progesterone itself, because progesterone has a short-half life. These include:
** Fluorogestone acetate (FGA)
** Medroxyprogesterone acetate (MAP)

==== Intravaginal Sponges ====

* The sponge is impregnated with progestogens and inserted into the vagina.
* Progestogen is absorbed in sufficient quantities to cause a negative feedback effect on pituitary function.
* When used outside of the normal breeding season, eCG is administered at the end of the progestogen priming period.
* Fertility may be reduced at first mating after synchronized oestrus. This may be due to poor absorbtion of progestogen from the sponge. It may also be the effect of abnormal hormone levels on sperm survival.

=== Pharmacological: Prostaglandins ===

* Used to induce luteal regression and subsequent cyclicity in cyclic ewes.
* Administration of PGF2α or its analogues during the period when there is a sensitive corpus luteum present induces oestrus 36-46 hours after injection.
* Ovulation will then occur shortly afterwards.
* In order to synchronize a group of ewes in randomly different stages of the oestrous cycle, two injections are required 8-9 days apart in order to ensure administration at a time when there is a sensitive corpus luteum present in all animals of the group.
* Uses are limited for a number of reasons:
** Having to give two injections is impractical under field conditions
** The induced oestrus leads to poor fertility, probably due to the limited exposure of the tract to progesterone.
** Prostaglandins can only be used in cyclic animals, not in seasonal anoestrus.
* It is usually only used in combination with progestogens.

=== Pharmacological: Melatonin ===

* Used comercially to advance the onset of the breeding season.
* The breeding season can be advanced by 2-3 months with good fertility.
* Administered as an implant containing 18mg of melatonin, which is inserted subcutaneously at the base of the ear.
* Ewes should be completely isolated from rams at least 7 days before insertion of the implant.
* They should remain separated for at least 30 days, and no more than 40 days.
* Rams should then be reintroduced.
* Peak mating activity occurs 25-35 days later.
* However, this is much work for little benefit because it cannot be used for ewes in deep anoestrus.

=== Immunization ===

* Use of an immunogen, produced by conjugating a derivative of adrostenedione with human serum albumin, increases lambing rates.
* When injected, it stimulates the production of antibodies to androstenedione.
* The antibodies bind free androstendione in the blood.
* This results in an increase in the number of lambs born, although the precise reason for this is unknown.
* Inject twice:
** 8 weeks before tupping
** 4 weeks before tupping
* If ewes have been treated in the previous season, only one injection is required at 4 weeks before tupping.
* Only inject ewes which are to be fed adequately during pregnancy, due to the dangers of pregnancy toxaemia.
* Immunization against inhibin will soon be available for commercial use.
** This will reduce the inhibitory effect of inhibin on FSH secretion from the anterior pituitary gland.
** The subsequent increase in FSH will lead to an increase in the nuber of developing follicles, thus better lambing rates.

== Cow ==

=== Controlling Oestrous ===

* The main reasons for controlling oestrus are:
** Induction of oestrus in dairy cows that are not observed in oestrus by 45 days post-partum.
** Synchronization of groups of heifers for insemination with semen of 'easy calving' bulls.
** Reducuction in the time necessary for oestrus detection.
** To facillitate the use of artificial insemination.
** Synchronization of donor and recipient cows for embryo transfer.
** Induction of ovarian activity in beef cows with lactational anoestrus.

=== Pharmacological: Gonadotrophins ===

* eCG can be used to stimulate follicular growth and ovulation in the anoestrus cow.
* Dose response is variable and can result in multiple ovulations.
* Withold insemination at the induced oestrus.
* The cow often returns to anoestrus, so overall the use of eCH is not recommended.

=== Pharmacological: Prostaglandins ===

* Used to synchronize oestrus in groups of cows and heifers. Oestrus detection is difficult in this species, so this is advantageous for optimum timing of artificial insemination.
* Give two injections of PGF2α or an analogue such as cloprostenol at an interval of 11 days to a group of cows/heifers all at different stages of the oestrous cycle.
* 3-5 days after the second injection, all animals treated will come into oestrus and ovulate at about the same time.
* If only a single injection is given, conception rates are lower after subsequent artificial insemination.
* Two injections are required in order to ensure the prostaglandins are administered to all animals in a period where the corpus luteum is sensitive.
* To reduce cost and improve pregnancy rates, the following regime is used:
** All animals are injected with PGF2α on the same day and observed for oestrus during the following 5 days.
* The length of time between the injection and onset of oestrus does vary slightly, depending on the ovarian status at the time of the injection. If there is a large, dominant follicle, the time until oestrus onset will be short, whereas if only small follicles are present, the period will be longer.
* Lactating dairy cows have a more variable interval between the injection and onset of oestrus.
** Any identified in oestrus are inseminated
** Any not identified as being in oestrus receive a second injection of prostaglandin followed by artificial insemination.
** Any animals that exhibit oestrus following the first insemination are reinseminated.

=== Pharmacological: Progestogens ===

* Used to synchronize groups of cows and heifers for artificial insemination and to overcome problems with oestrus detection.
* Treatment of random cycling animals for 18-21 days results in synchronization of oestrus.
* When the treatment ceases, oestrus occurs in 4-6 days.
* Fertility at first oestrus is lower, due to impaired sperm transort as a result of the atypical hormone balance after treatment is withdrawn.
* To ensure the natural corpus luteum of the cycle has regressed by the time of progestogen withdrawal, progestogen treatment is often combined with a luteolytic factor:
** Oestradiol at the start of treatment or prostaglandin analogues at the end of treatment.
** Oestradiol is best because as well as inducing luteal regression, it affects follicular dynamics so improves fertility at first oestrus.
* In non-cyclic cows, progestogens sensitize the hypothalamic-anterior pituitary-gonadal axis. This approach can be used in cattle with innactive ovaries.
* Injecting with eCG at progestogen removal stimulates follicular maturation and ovulation.
* Oestrus and ovulation after treatment with progestogens occurs earlier and with more precise timing than following injection of prostaglandin alone.

==== Progesterone Releasing Intravaginal Device (PRID) ====

* Stainless steel coil covered with an inert elastomer incorporating 1.55g of progesterone.
* Placed in the vagina using a speculum.
* Whilst in place, progesterone is absorbed to produce plasma concentrations that mimic maximum levels at dioestrus.
* When removed after 12 days, the cow will come into oestrus in 2-3 days.
* Some may also contain Oestradiol Benzoate.
* Oestradiol Benzoate is anti-luteotrophic and mildly luteolytic.
* Almost 100% synchronization can be achieved if an injection of PGF2α is administered 24 hours before removing the device. This has a far greater luteolytic effect than Oestradiol Benzoate alone.
* Can be used in cyclic cows to synchronize oestrus, best inserted on day 13-14.
* Can be used in anoestrus dairy and beef cows to induce oestrus.

==== Controlled Internal Drug Release Device (CIDR) ====

* A hinged T-shaped device impregnated with progesterone.
* Placed in the vagina using a speculum.
* Whilst in place, progesterone is absorbed to produce plasma concentrations that mimic maximum levels at dioestrus.
* When removed after 12 days, the cow will come into oestrus in 2-3 days.
* Can be used in cyclic cows to synchronize oestrus, best inserted on day 13-14.
* Can be used in anoestrus dairy and beef cows to induce oestrus.

== Mare ==

=== Reasons to Control the Oestrous Cycle ===

* Better planning in studs
* Synchronizing the donor and recipient for embryo transfer.
* In racehorses, performance of 2-year olds is important. The age of a horse is measured from 1st January, so it is important that foals are born as soon as possible after 1st January in order to produce the oldest '2 year old' possible.

=== Control in the Transition Period ===

* Day length is an important stimulus for cyclicity.
* Aim is to simulate the natural photoperiod that would occur later on in the year.
* Exposure to ~116 hours of daylight in mid-November can advance the first ovulation from early April to early February.
* Combining photoperiod manipulation with GnRH achieved optimal results.

=== Control in the Breeding Period ===

* During the natural breeding period, manipulation is mainly carried out to treat fertility disorders.
** Prolonged oestrus can be treated with a Progesterone Rleasing Intravaginal Device (PRID)
** A persistent corpus luteum can be treated with prostaglandins.
* Other reasons for manipulation include:
** Shortening anoestrus after foaling
** Synchronizing oestrus in a group of mares

===== Pharmacological: Progestogens =====

* In competition horses, it is desirable to prevent the mare from coming into oestrus at inopportune times.
* In some cases it is desirable to synchronize a group of animals.
* A daily injection of progesterone (0.3mg/Kg) will prevent oestrus.
* The mare will return to oestrus 3-7 days after treatment ceases.
* Oral progestoges recommended include:
** Allytrenbolone
** Altrenogest
* These can be used in a number of ways:
1. '''To stimulate the onset of cyclic activity'''
* Administer 0.044mg/Kg mixed in with the feed for 10 days and then stop.
* Give in the late transition period from anoestrus to cyclic activity when follicles are present.
* Better results when combined with increased lighting.
2. '''To suppress oestrus for an event'''
* Feed for 15 days at 0.044mg/Kg
3. '''To suppress oestrus in mares with prolonged oestrus'''
4. '''To control the time of oestrus for effective use of the stallion'''
* Feed for 15 days, then stop.
* Mare should come into oestrus 2-3 days later.

===== Pharmacological: Prostaglandins =====

* Eliminates the need for frequent testing for oestrus. It is also useful if a heat is missed, particularly the 'foal heat'.
* PGF2α and the synthetic analogue clonprostenol are used.
* Onset of oestrus is well synchronized 3 days after treatment.
* Subsequent ovulation occurs 7-12 days after treatment.
* Injecting hCG or GnRH on day 2-3 of the induced oestrus achieves the best results.

=== Inducing Ovulation ===

* The main method is the use of hCG
* In the presence of a follicle >2.5 cm, hCG will induce ovulation 24-48 (on average 35) hours after administration.

== Sow ==

=== Pharmacological: Progestagens ===

* Used to synchronize cyclic gilts and sows
* Difficult to treat group-fed animals, since it is contraindicated for pregnant animals and boars.
* Progestogens used are:
** Altrenogest
** Allytrenbolone
* Supress follicular maturation when fed daily at 15-20mg with no effect on the life span of corpora lutea.
* Feed for 18 days to achieve synchronization of oestrus 5-7 days after withdrawal.

=== Pharmacological: Prostaglandins ===

* Theoretically gives reliable synchronization of oestrus in groups of gilts and sows.
* Enables ease of artificial insemination and batch farrowing.
* But, prostaglandins and their analogues are not luteolytic until day 11-12 of the oestrous cycle.
* Thus, an injection regime for groups of animals at random periods of the oestrous cycle is not possible.
* However, it is possible after injection of oestrogen (see below)
* Another indication for use of prostaglandins is to induce luteolysis of accessory corpora lutea after use of eCG or hCG at any stage of the oestrous cycle.

=== Pharmacological: Oestrogens ===

* Prolong the lifespan of corpora lutea
* Inject oestrogen on day 10-14 of the oestrus cycle.
* Then, prostaglandins can be injected after 5-20 days.
* Oestrus will occur 4-6 days later.

=== Pharmacological: Gonadotrophins ===

* In anoestrus gilts and sows eCG, or a combination of eCG and hCG will promote follicular growth and oestrus.
* If this is followed by another injection of hCG 72 hours later, this will ensure ovulation occurs.
* This can also be used to synchronize cyclic activity, especially if used in combination with progestogen.

== Bitch ==

=== Pharmacological: Gonadotrophins ===

* Combinations of eCG and hCG can induce oestrus in the anoestrus bitch.
* Sometimes this is combined with oestrogens.
* However, conception rates after the induced ovulation tend to be poor.

=== Pharmacological: Synthetic Progestogens ===

* Used to suppress oestrus.
* Commonly used progestogens include:
** Megoestrol acetate
** Proligestone
** Medroxyprogesterone
* These are available orally or for injection.
* They can be used to postpone the onset of oestrus when administered during anoestrus.
** Can be postponed for up to a year by injecting progestogens at intervals of 3-5 months or giving a 40 day course of oral tablets twice a week.
* Another use is to prevent oestrus from occuring if administered at the fist signs of pro-oestrus.
** This is achieved by a single injection or oral progestogen at a higher dose rate than for postmonement, but for a shorter duration.
* Following administration of progestogens, the interval before onset of the next oestrus is unpredictable if treatment is not continued.
* Frequent use can predispose the bitch to reproductive disorders, particularly cystic glandular hyperplasia of the endometrium.
* First generation progestogens such as Medroxyprogesterone acetate (MPA) carry the risk of stimulating growth hormone (GH) secretion. This leads to an increased risk of acromegaly, mammary tumours and diabetes mellitus.

==== Proligestone (PRG) ====

* A new drug specifically designed to prevent oestrus in bitches and queens.
* It is particularly suitable because:
** Strongly anti-gonadotrophic
** Weakly progestagenic
** Antioestrogenic, so effectively controls vulval swelling and bleeding.

== Queen ==

Suppression of oestrus may be desireable for a number of reasons, but mostly to plan litters throughout the year and allow the queen a rest from sexual activity after a litter. This allows the queen to regain condition before being bred again. If the queen is allowed to call without mating, it may lead to loss in condition due to innapetance during oestrus.

=== Physiological ===

* Pseudopregnancy can be achieved by mating queens with a castrated Tom, or through stimulating coitus by swabbing the vagina.
* Pseudopregnant queens will not return to oestrus for 4-8 weeks.

=== Pharmacological: hCG ===

* Administration of hCG can be used to induce ovulation.
* This will cause pseudopregnancy.
* Pseudopregnant queens will not return to oestrus for 4-8 weeks.

=== Pharmacological: Androgens ===

* Androgen anabolic steroids used daily postpone calling.
* Give daily oral doses ~30 days before anticipated oestrus.
* Induces masculinization

=== Pharmacological: Progestogens ===

* Used to suppress oestrus
* Injectable forms include:
** Medroxyprogesterone acetate
*** Will suppress oestrus for 7 months or more following a single injection
*** Can be repeated every 5 months to achieve permanent oestrus suppression.
** Proligestone
* Oral progestogens are more flexible.
* The most commonly used oral progestogen is Megoestrol acetate.
** Used to prevent oestrus period by administering 5mg as soon as signs of oestrus are observed.
** Postponment is achieved by administering 2.5mg daily or weekly depending on whether the treatment is in the breeding season or the period of anoestrus.
* Side effects include lethargy and weight gain, there is also a predisposal to diabetes mellitus.

[[Category:Female Reproduction]][[Category:Pharmacology]]
[[Category:Bullet Points]]

Oestrous Cycle Pharmacological Manipulation - Anatomy & Physiology

2013-12-19T07:37:42Z

Vulpesferrilata: /* Light */

= Introduction =

The manipulation of normal cyclic activity ensures optimum production or is convenient for the herdsmen or owner. In the case of seasonal breeders, it allows them to breed out of season, or to advance the onset of cyclic activity. There are also advantages in ensuring all animals in a group come into oestrus at the same time for ease of management.
There are two methods of oestrus synchronisation. One is physiological manipulation of the oestrous cycle, and the other pharmacological manipulation of the cycle. Various factors must be considered before deciding which method to use. These factors will be specific to the type of production unit and species, also the stage of the natural oestrous cycle in the animal/herd involved.

= Factors Influencing Reproduction =

== Physiological ==

=== Light ===

* Cyclic activity in the mare, ewe, goat and cat depend on changes in the number of daylight hours.
* Tungsten and fluorescent lamps can be used to artificially manipulate the photoperiod.
* Mare and queen are stimulated by increasing day length (long day breeders)
** If mares are stabled in December and exposed to artificial light for increasing duration, the onset of oestrous cyclicity and ovulation wil be advanced.
* Ewe and goat are stimulated by decreasing day length (short day breeders)
** Providing ewes with controlled light housing enables change in the breeding season from autumn and winter to spring and summer.
** If there is no change in duration of light stiulus, it is possible to make ewes cycle all year round.

=== Nutrition ===

* Improved nutrition prior to mating (flushing) will increase the number of follicles which mature and ovulate.
* Used in the ewe and sow successfully.

=== Other Methods ===

* The presence of a male can stimulate the onset of cyclic activity in some species (see 'Ram Effect' for more detail).
* In sows and gilts, removing piglets will cause a more rapid return to cyclic activity post-partum.
* If litters are weaned from a group of sows at the same time, there will also be some synchronisation of oestrus.
* Also in gilts and sows, the stress of changing environment or transport stress can stimulate the onset of oestrus post-partum.

== Pharmacalogical ==

=== Preparations which Stimulate Release of Anterior Pituitary Hormones ===

* Ovarian steroids, particularly oestrogens, exert a positive-feedback on the anterior pituitary gland and hypothalamus.
* Oestrogens and synthetic oestrogens are used to stimulate oestrus.
* They have a direct effect on stimulating oestrus behaviour and changes in the genital tract.
* They may also stimulate release of pituitary gonadotrophins.
* Synthetic GnRH can be used to stimulate the release of endogenous gonadotrophins.

=== Preparations which Supplement or Replace Pituitary Gonadotrophins ===

* Purified LH and FSH can be extracted from the pituitary gland in the abbatoir, but this is too time consuming to be practiced commercially. There is also the risk of transmitting diseases such as BSE.
* Instead, two substitutes are used commercially:
** Equine Chorionic Gonadotrophin (eCG): obtained from the serum of pregnant mares. This has an 'FSH-like' effect, but with some 'LH-like' activity.
** Human Chorionic Gonadotrophin (hCG): obtained from the urine of pregnant women. It has mainly an 'LH-like' effect, but with some 'FSH-like' activity.

=== Oestrogens ===

* Used to induce oestrus in anoestrous animals.
* Have a direct effect on oestrus behaviour and the genital tract.
* May inhibit the pituitary release of gonadotrophins in high doses.
* Do not initiate ovarian activity or ovulation.

=== Progestogens ===

* Progesterone and its synthetic analogues are used extensively in most domestic species to synchronize oestrus.
* Exogenous progestogens act in the same way as the corpus luteum, resulting in a negative feedback effect on the anterior pituitary gland.
* This in turn results in supression of gonadotrophin release, so cyclic activity ceases.
* When the progestogen is withdrawn, the negative feedback block on the anterior pituitary gland is removed. This initiates a retun to cyclic activity.

=== Prostaglandins ===

* The length of the interoestrus interval in most domestic species is controlled by the duration of the lifespan of the corpus luteum.
* Administration of PGF2α or its analogues will cause premature luteolysis of the corpus luteum.
* This can be used to manipulate the normal pattern of cyclic activity.
* Prostaglandins will induce luteal regression. As a result, progesterone levels fall and negative feedback on the anterior pituitary gland is removed. Subsequently, levels of gonadotrophins begin to rise, leading to increased follicular growth under the influence of FSH. Oestradiol production begins to rise as follicles become dominant. When oestradiol rises above the threshold, it feeds back positively at the level of the hypothalamus. The hypothalamus then releases a surge of GnRH. This then stimulates the anterior pituitary gland to release a surge of LH which is responsible for ovulation.
* The corpora lutea of the cow, mare, sow, ewe and goat respond to administration of exogenous prostaglandins.
* In the cow, mare, ewe and goat the new developing corpus luteum is refractory to prostaglandins for 3-5 days after ovulation.
* At the end of the cycle, the corpus luteum is unaffected by exogenous prostaglandin because it is already regressing under the influence of its own endogenous luteolytic hormones.
* The corpus luteum is resonsive for:
** Cow: 13 days
** Goat: 13 days
** Mare: 10 days
** Ewe: 9 days
* In the sow, the corpus luteum is refractory for up to 11 days after ovulation. It is only resposive for a period of 7-8 days.
* In the bitch and queen, corpora lutea are unresponsive to exogenous prostaglandins unless they are given repeated doses.
* Prostaglandins will cause abortion, do not use in animals that might be pregnant!

=== Melatonin ===

* The pineal gland controls reproductive cyclicity in seasonal breeders (sheep, goats, horses and cats) by the secretion of melatonin as the daylight hours are reduced. For more information on this mechanism, click [[Seasonality_of_Reproduction_- Anatomy & Physiology#Mechanism_of_seasonality|here]]
* Melatonin can be used successfully to modify seasonal activity in the species mentioned, most practically the ewe.

= Manipulation of the Oestrous Cycle in Various Species =

== Ewe ==

True synchronization in the ewe is not achieved even with the combined use of prostaglandins and progestogens with much time and effort under controlled conditions of a lab setting. Thus, in practice these methods are never completely effective for the ewe.

=== Factors to Consider Before Deciding which Method to Use ===

* Degree of synchronization required
* The season
* Economic and market factors
* Physiological manipulation is usually cheaper, but it does not result in tight synchronization and can only be used under certain conditions.
* Pharmacological methods tend to give tight synchronization throughout the year, but are more expensive in terms of both drugs and labour.

=== Physiological: The Ram Effect ===

* Ram stimulate gonadotrophin secretion form the anterior pituitary gland and subsequent ovulation in anoestrus ewes through chemosensory cues.
* Isolate ewes for 3-4 weeks before introducing the ram.
* Only effective at certain times of the year - just before commencement of the natural breeding season. This method is not effective for ewes in deep anoestrus.
* The majority of ewes ovulate within 6 days of introducing the ram.
* Priming with progesterone (intravaginal sponge or intramuscular injection) prior to the introduction of the ram will increase the percentage of ewes showing oestrus behaviour.
* Cheap and easy, but not very effective as a sole method.

=== Pharmacological: Gonadotrophins ===

* Use of eCG alone to induce oestrus in anoestrus ewes is not very successful.
* Administration of progesterone before the injection of eCG causes synchronised oestrus and ovulation in seasonally anoestrus ewes.

=== Pharmacological: Progestogens ===

* Used alone or in conjunction with other hormones.
* Used to induce oestrus in the anoestrus ewe during the non-breeding season and for oestrus synchronization in cyclic ewes.
* To be effective, treatment must last for the length of the normal luteal phase (12-14 days).
* In the anoestrus ewe, progesterone withdrawal is complemented by follicle stimulating treatments such as eCG. This will stimulate oestradiol secretion due to its 'FSH-like' effect.
* Progestogens are now used more commonly than progesterone itself, because progesterone has a short-half life. These include:
** Fluorogestone acetate (FGA)
** Medroxyprogesterone acetate (MAP)

==== Intravaginal Sponges ====

* The sponge is impregnated with progestogens and inserted into the vagina.
* Progestogen is absorbed in sufficient quantities to cause a negative feedback effect on pituitary function.
* When used outside of the normal breeding season, eCG is administered at the end of the progestogen priming period.
* Fertility may be reduced at first mating after synchronized oestrus. This may be due to poor absorbtion of progestogen from the sponge. It may also be the effect of abnormal hormone levels on sperm survival.

=== Pharmacological: Prostaglandins ===

* Used to induce luteal regression and subsequent cyclicity in cyclic ewes.
* Administration of PGF2α or its analogues during the period when there is a sensitive corpus luteum present induces oestrus 36-46 hours after injection.
* Ovulation will then occur shortly afterwards.
* In order to synchronize a group of ewes in randomly different stages of the oestrous cycle, two injections are required 8-9 days apart in order to ensure administration at a time when there is a sensitive corpus luteum present in all animals of the group.
* Uses are limited for a number of reasons:
** Having to give two injections is impractical under field conditions
** The induced oestrus leads to poor fertility, probably due to the limited exposure of the tract to progesterone.
** Prostaglandins can only be used in cyclic animals, not in seasonal anoestrus.
* It is usually only used in combination with progestogens.

=== Pharmacological: Melatonin ===

* Used comercially to advance the onset of the breeding season.
* The breeding season can be advanced by 2-3 months with good fertility.
* Administered as an implant containing 18mg of melatonin, which is inserted subcutaneously at the base of the ear.
* Ewes should be completely isolated from rams at least 7 days before insertion of the implant.
* They should remain separated for at least 30 days, and no more than 40 days.
* Rams should then be reintroduced.
* Peak mating activity occurs 25-35 days later.
* However, this is much work for little benefit because it cannot be used for ewes in deep anoestrus.

=== Immunization ===

* Use of an immunogen, produced by conjugating a derivative of adrostenedione with human serum albumin, increases lambing rates.
* When injected, it stimulates the production of antibodies to androstenedione.
* The antibodies bind free androstendione in the blood.
* This results in an increase in the number of lambs born, although the precise reason for this is unknown.
* Inject twice:
** 8 weeks before tupping
** 4 weeks before tupping
* If ewes have been treated in the previous season, only one injection is required at 4 weeks before tupping.
* Only inject ewes which are to be fed adequately during pregnancy, due to the dangers of pregnancy toxaemia.
* Immunization against inhibin will soon be available for commercial use.
** This will reduce the inhibitory effect of inhibin on FSH secretion from the anterior pituitary gland.
** The subsequent increase in FSH will lead to an increase in the nuber of developing follicles, thus better lambing rates.

== Cow ==

=== Controlling Oestrous ===

* The main reasons for controlling oestrus are:
** Induction of oestrus in dairy cows that are not observed in oestrus by 45 days post-partum.
** Synchronization of groups of heifers for insemination with semen of 'easy calving' bulls.
** Reducuction in the time necessary for oestrus detection.
** To facillitate the use of artificial insemination.
** Synchronization of donor and recipient cows for embryo transfer.
** Induction of ovarian activity in beef cows with lactational anoestrus.

=== Pharmacological: Gonadotrophins ===

* eCG can be used to stimulate follicular growth and ovulation in the anoestrus cow.
* Dose response is variable and can result in multiple ovulations.
* Withold insemination at the induced oestrus.
* The cow often returns to anoestrus, so overall the use of eCH is not recommended.

=== Pharmacological: Prostaglandins ===

* Used to synchronize oestrus in groups of cows and heifers. Oestrus detection is difficult in this species, so this is advantageous for optimum timing of artificial insemination.
* Give two injections of PGF2α or an analogue such as cloprostenol at an interval of 11 days to a group of cows/heifers all at different stages of the oestrous cycle.
* 3-5 days after the second injection, all animals treated will come into oestrus and ovulate at about the same time.
* If only a single injection is given, conception rates are lower after subsequent artificial insemination.
* Two injections are required in order to ensure the prostaglandins are administered to all animals in a period where the corpus luteum is sensitive.
* To reduce cost and improve pregnancy rates, the following regime is used:
** All animals are injected with PGF2α on the same day and observed for oestrus during the following 5 days.
* The length of time between the injection and onset of oestrus does vary slightly, depending on the ovarian status at the time of the injection. If there is a large, dominant follicle, the time until oestrus onset will be short, whereas if only small follicles are present, the period will be longer.
* Lactating dairy cows have a more variable interval between the injection and onset of oestrus.
** Any identified in oestrus are inseminated
** Any not identified as being in oestrus receive a second injection of prostaglandin followed by artificial insemination.
** Any animals that exhibit oestrus following the first insemination are reinseminated.

=== Pharmacological: Progestogens ===

* Used to synchronize groups of cows and heifers for artificial insemination and to overcome problems with oestrus detection.
* Treatment of random cycling animals for 18-21 days results in synchronization of oestrus.
* When the treatment ceases, oestrus occurs in 4-6 days.
* Fertility at first oestrus is lower, due to impaired sperm transort as a result of the atypical hormone balance after treatment is withdrawn.
* To ensure the natural corpus luteum of the cycle has regressed by the time of progestogen withdrawal, progestogen treatment is often combined with a luteolytic factor:
** Oestradiol at the start of treatment or prostaglandin analogues at the end of treatment.
** Oestradiol is best because as well as inducing luteal regression, it affects follicular dynamics so improves fertility at first oestrus.
* In non-cyclic cows, progestogens sensitize the hypothalamic-anterior pituitary-gonadal axis. This approach can be used in cattle with innactive ovaries.
* Injecting with eCG at progestogen removal stimulates follicular maturation and ovulation.
* Oestrus and ovulation after treatment with progestogens occurs earlier and with more precise timing than following injection of prostaglandin alone.

==== Progesterone Releasing Intravaginal Device (PRID) ====

* Stainless steel coil covered with an inert elastomer incorporating 1.55g of progesterone.
* Placed in the vagina using a speculum.
* Whilst in place, progesterone is absorbed to produce plasma concentrations that mimic maximum levels at dioestrus.
* When removed after 12 days, the cow will come into oestrus in 2-3 days.
* Some may also contain Oestradiol Benzoate.
* Oestradiol Benzoate is anti-luteotrophic and mildly luteolytic.
* Almost 100% synchronization can be achieved if an injection of PGF2α is administered 24 hours before removing the device. This has a far greater luteolytic effect than Oestradiol Benzoate alone.
* Can be used in cyclic cows to synchronize oestrus, best inserted on day 13-14.
* Can be used in anoestrus dairy and beef cows to induce oestrus.

==== Controlled Internal Drug Release Device (CIDR) ====

* A hinged T-shaped device impregnated with progesterone.
* Placed in the vagina using a speculum.
* Whilst in place, progesterone is absorbed to produce plasma concentrations that mimic maximum levels at dioestrus.
* When removed after 12 days, the cow will come into oestrus in 2-3 days.
* Can be used in cyclic cows to synchronize oestrus, best inserted on day 13-14.
* Can be used in anoestrus dairy and beef cows to induce oestrus.

== Mare ==

=== Reasons to Control the Oestrous Cycle ===

* Better planning in studs
* Synchronizing the donor and recipient for embryo transfer.
* In racehorses, performance of 2-year olds is important. The age of a horse is measured from 1st January, so it is important that foals are born as soon as possible after 1st January in order to produce the oldest '2 year old' possible.

=== Control in the Transition Period ===

* Day length is an important stimulus for cyclicity.
* Aim is to simulate the natural photoperiod that would occur later on in the year.
* Exposure to ~116 hours of daylight in mid-November can advance the first ovulation from early April to early February.
* Combining photoperiod manipulation with GnRH achieved optimal results.

=== Control in the Breeding Period ===

* During the natural breeding period, manipulation is mainly carried out to treat fertility disorders.
** Prolonged oestrus can be treated with a Progesterone Rleasing Intravaginal Device (PRID)
** A persistent corpus luteum can be treated with prostaglandins.
* Other reasons for manipulation include:
** Shortening anoestrus after foaling
** Synchronizing oestrus in a group of mares

===== Pharmacological: Progestogens =====

* In competition horses, it is desirable to prevent the mare from coming into oestrus at inopportune times.
* In some cases it is desirable to synchronize a group of animals.
* A daily injection of progesterone (0.3mg/Kg) will prevent oestrus.
* The mare will return to oestrus 3-7 days after treatment ceases.
* Oral progestoges recommended include:
** Allytrenbolone
** Altrenogest
* These can be used in a number of ways:
1. '''To stimulate the onset of cyclic activity'''
* Administer 0.044mg/Kg mixed in with the feed for 10 days and then stop.
* Give in the late transition period from anoestrus to cyclic activity when follicles are present.
* Better results when combined with increased lighting.
2. '''To suppress oestrus for an event'''
* Feed for 15 days at 0.044mg/Kg
3. '''To suppress oestrus in mares with prolonged oestrus'''
4. '''To control the time of oestrus for effective use of the stallion'''
* Feed for 15 days, then stop.
* Mare should come into oestrus 2-3 days later.

===== Pharmacological: Prostaglandins =====

* Eliminates the need for frequent testing for oestrus. It is also useful if a heat is missed, particularly the 'foal heat'.
* PGF2α and the synthetic analogue clonprostenol are used.
* Onset of oestrus is well synchronized 3 days after treatment.
* Subsequent ovulation occurs 7-12 days after treatment.
* Injecting hCG or GnRH on day 2-3 of the induced oestrus achieves the best results.

=== Inducing Ovulation ===

* The main method is the use of hCG
* In the presence of a follicle >2.5 cm, hCG will induce ovulation 24-48 (on average 35) hours after administration.

== Sow ==

=== Pharmacological: Progestagens ===

* Used to synchronize cyclic gilts and sows
* Difficult to treat group-fed animals, since it is contraindicated for pregnant animals and boars.
* Progestogens used are:
** Altrenogest
** Allytrenbolone
* Supress follicular maturation when fed daily at 15-20mg with no effect on the life span of corpora lutea.
* Feed for 18 days to achieve synchronization of oestrus 5-7 days after withdrawal.

=== Pharmacological: Prostaglandins ===

* Theoretically gives reliable synchronization of oestrus in groups of gilts and sows.
* Enables ease of artificial insemination and batch farrowing.
* But, prostaglandins and their analogues are not luteolytic until day 11-12 of the oestrous cycle.
* Thus, an injection regime for groups of animals at random periods of the oestrous cycle is not possible.
* However, it is possible after injection of oestrogen (see below)
* Another indication for use of prostaglandins is to induce luteolysis of accessory corpora lutea after use of eCG or hCG at any stage of the oestrous cycle.

=== Pharmacological: Oestrogens ===

* Prolong the lifespan of corpora lutea
* Inject oestrogen on day 10-14 of the oestrus cycle.
* Then, prostaglandins can be injected after 5-20 days.
* Oestrus will occur 4-6 days later.

=== Pharmacological: Gonadotrophins ===

* In anoestrus gilts and sows eCG, or a combination of eCG and hCG will promote follicular growth and oestrus.
* If this is followed by another injection of hCG 72 hours later, this will ensure ovulation occurs.
* This can also be used to synchronize cyclic activity, especially if used in combination with progestogen.

== Bitch ==

=== Pharmacological: Gonadotrophins ===

* Combinations of eCG and hCG can induce oestrus in the anoestrus bitch.
* Sometimes this is combined with oestrogens.
* However, conception rates after the induced ovulation tend to be poor.

=== Pharmacological: Synthetic Progestogens ===

* Used to suppress oestrus.
* Commonly used progestogens include:
** Megoestrol acetate
** Proligestone
** Medroxyprogesterone
* These are available orally or for injection.
* They can be used to postpone the onset of oestrus when administered during anoestrus.
** Can be postponed for up to a year by injecting progestogens at intervals of 3-5 months or giving a 40 day course of oral tablets twice a week.
* Another use is to prevent oestrus from occuring if administered at the fist signs of pro-oestrus.
** This is achieved by a single injection or oral progestogen at a higher dose rate than for postmonement, but for a shorter duration.
* Following administration of progestogens, the interval before onset of the next oestrus is unpredictable if treatment is not continued.
* Frequent use can predispose the bitch to reproductive disorders, particularly cystic glandular hyperplasia of the endometrium.
* First generation progestogens such as Medroxyprogesterone acetate (MPA) carry the risk of stimulating growth hormone (GH) secretion. This leads to an increased risk of acromegaly, mammary tumours and diabetes mellitus.

==== Proligestone (PRG) ====

* A new drug specifically designed to prevent oestrus in bitches and queens.
* It is particularly suitable because:
** Strongly anti-gonadotrophic
** Weakly progestagenic
** Antioestrogenic, so effectively controls vulval swelling and bleeding.

== Queen ==

Suppression of oestrus may be desireable for a number of reasons, but mostly to plan litters throughout the year and allow the queen a rest from sexual activity after a litter. This allows the queen to regain condition before being bred again. If the queen is allowed to call without mating, it may lead to loss in condition due to innapetance during oestrus.

=== Physiological ===

* Pseudopregnancy can be achieved by mating queens with a castrated Tom, or through stimulating coitus by swabbing the vagina.
* Pseudopregnant queens will not return to oestrus for 4-8 weeks.

=== Pharmacological: hCG ===

* Administration of hCG can be used to induce ovulation.
* This will cause pseudopregnancy.
* Pseudopregnant queens will not return to oestrus for 4-8 weeks.

=== Pharmacological: Androgens ===

* Androgen anabolic steroids used daily postpone calling.
* Give daily oral doses ~30 days before anticipated oestrus.
* Induces masculinization

=== Pharmacological: Progestogens ===

* Used to suppress oestrus
* Injectable forms include:
** Medroxyprogesterone acetate
*** Will suppress oestrus for 7 months or more following a single injection
*** Can be repeated every 5 months to achieve permanent oestrus suppression.
** Proligestone
* Oral progestogens are more flexible.
* The most commonly used oral progestogen is Megoestrol acetate.
** Used to prevent oestrus period by administering 5mg as soon as signs of oestrus are observed.
** Postponment is achieved by administering 2.5mg daily or weekly depending on whether the treatment is in the breeding season or the period of anoestrus.
* Side effects include lethargy and weight gain, there is also a predisposal to diabetes mellitus.

[[Category:Female Reproduction]][[Category:Pharmacology]]
[[Category:Bullet Points]]

Strongyloides

2013-06-12T13:18:34Z

Vulpesferrilata: /* Life-Cycle */

{{Taxobox
|name =''Strongyloides spp.''
|kingdom =Animalia
|sub-kingdom =
|phylum =[[:Category:Nematodes|Nematoda]]
|super-class =
|class = Chromadorea
|sub-class =
|super-order =
|order = Rhabditida
|sub-order = Rhabditina
|super-family =Rhabditoidea
|family =Strongyloididae
|sub-family =
|genus =Strongloides
|species =''S. westeri''
}}
[[Image:Strongyloides stercoralis 2.jpg|thumb|right|150px|''Strongyloides stercoralis'' - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine]]
[[Image:Strongyloides stercoralis.jpg|thumb|right|150px|''Strongyloides stercoralis'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
[[Image:Strongyloides larvae.jpg|thumb|right|150px|''Strongyloides'' larvae - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
[[Image:Strongyloides.jpg|thumb|right|150px|''Strongyloides'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
==Overview==
This is the only genus of veterinary importance in the super-family Rhabditoidea. There are a number of species that are of particular importance and these are mainly host specific.

=== ''Strongyloides westeri'' ===
This is a parasite of the horse and is most commonly seen in young foals, less than six months in age. This is usually the fisrt parasite to which foals are exposed and therfore they have very little immunity to these infections. The predeliction site for these worms is the small intestine.
==== Morphology ====
The distinguishing features of this worm are:
*Very small, 6-9mm long
*Slender, hair-like
*Long oesophagus (up to one third of body length).
*Intestines and ovaries intertwined in caudal body
*Blunt ended tail
The eggs are small and oval with a thin shell, they will often hatch in the large intestine so L1 larvae are expelled in the hosts faeces.
==== Life-Cycle ====
''S. westeri'' has a typical [[:Category:Rhabditoidea|strongyloides]] life cycle, with both a free living and parasitic cycle. The free living cycle involves male and female worms reproducing sexually on the ground, this can occur for several generation with no parasitism taking place. The parasitic phase involves only female worms and occurs from ingesion of L3 larvae or their penetration through the hosts skin. Infection my also be transmissed vertically from the dam to the foal by larval migration to the mammary tissue and ingestion by the foal with the dams milk. Once in the host the larvae migrate to the small intestine where they tunnel into the epithelium at the base of the villi and moult to L4 and then adult females. Females produce eggs without sexual interaction that can develop to become both male and female larvae. The pre patent period is between 1 and 2 weeks dependant on the level of infection.

==== Pathogenicity ====
Pathology is rarely seen in adult horses due to the development of immunity, though penetration of the skin by larvae may still cause irritation anddermatitis. Adults with larvae in beneath the skin and in the abdomen can act as carriers. In foals heavy infections can cause severe enteritis and diarrhoea. It should be noted that apparently healthy animals can still have high faecal egg counts.
==== Control ====
The number and spread of ''S. westeri'' is best controlled by good hygeine such as the removal of faeces from pasture and stabling and the provision of clean, dry bedding. Foals are often treated with anthelmintics at 2 weeks old against ''S. westeri''.

===''Strongyloides papillosus''===
This is a nematode of cattle and small ruminants and is found throughout the world. As with ‘’S. westeri’’ above clinical signs are normally only seen in young animals as older animals develop immunity.
====Morphology====
The morphology of ''S. papillosus’’ is the same as that of the ‘’S. westeri’’. The eggs hatch inside the host and so L1 larvae are released with the faeces.
====Life Cycle====
The life cylce of ''S. papillosus'' is typical of [[:Category:Rhabditoidea|strongyloides]] species with both parasitic and free living cycles. As adults animals will become immune to infection the primary method of infection for young animals is through the milk of the dam, this still involves only females as males are only present in the environment as 'free-living' nematodes.

[[Category:Rhabditoidea]][[Category:Horse Nematodes]][[Category:Sheep Nematodes]]
[[Category:To_Do_-_Parasites]][[Category:To Do - Major]]

Uncinaria stenocephala

2013-06-10T18:56:10Z

Vulpesferrilata: /* Epidemiology */

{{OpenPagesTop}}
{{Taxobox
|name =''Uncinaria stenocephala
|kingdom =Animalia
|phylum =[[Nematodes|Nematoda]]
|class =Secernentea
|sub-class =
|order =Strongylida
|super-family =[[Ancylostomatoidea]]
|family =Ancylostomatidae
|sub-family =
|genus =Uncinaria
|species =''U. stenocephala
}}

==Introduction==
[[File:Hookworms.jpg|thumb|Image of ''Ancylostoma caninum'' Copyright Joel Mills 2006 Wikimedia Commons]]
''Uncinaria stenocephala'' is a hookworm of dogs that belong to the superfamily [[:Category:Ancylostomatoidea|Ancylostomatoidea]]. This superfamily contains exotic hookworms that infect man and animals. Unlike the other dog hookworm, [[Ancylostoma caninum|''Ancylostoma caninum'']], ''U. stenocephala'' occurs in cool and temperate climates including that of the UK. The details of the life-cycle are given [[Ancylostomatoidea Life-Cycle|elsewhere]] but it should be noted that the infection is mainly acquired by ingestion of L3 larvae and, unlike ''A. caninum'', L3 larvae are not passed to neonates by the trans-mammary route.

==Identification==
''U. stenocephala'' can be recognised on examination under a microscope by its large, dorsally curved, buccal capsule which contains cutting plates at the ventral edge. A single pair of small teeth are also found within the ventral capsule. Adults bury their heads deep in the wall of the small intestine and feed on plugs of mucosa.

Like almost all hookworm eggs, those of ''U. stenocephala'' are oval in shape and around 50 um in diameter. The shell membrane is thin and transparent and, by the time the egg is passed in the faeces, it contains a segmented ovum at the 4 or 8 cell stage. In a tropical climate, the egg will hatch within 24 hours and only L1 larvae will then be detectable.

==Epidemiology==
The larvae of ''U. stenocephala'' require moist conditions for development to the L3 stage and clinical disease is reported most frequently in dogs kept in wet confined conditions where larvae build up to high levels. Common situations include grass runs, wet concrete pens (especially if the surface is very pitted and able to retain moisture) and in areas contaminated by foxes which also act as definitive hosts. Certain groups of dogs are therefore particularly affected, including '''greyhounds''' in densely-populated racing kennels, '''fox hounds''', '''sheepdogs''' and dogs in '''rural environments'''. Since eggs also require warmth for development, most infections are also seen in summer.

==Clinical Disease==
Since adult worms are mucosal plug feeders, anaemia is not usually a feature of infection with ''U. stenocephala'' and most infections are asymptomatic. Where clinical signs are seen, the following patterns may be expected:
*'''[[Protein Losing Enteropathy|Protein-losing enteropathy]]''' caused by loss of protein to adults feeding in the small intestine.
*'''[[Hookworm Dermatosis|Dermatitis]]''' caused by the cutaneous migration of L3 larvae that are killed before they are able to enter the blood. Larvae which penetrate the skin rarely develop to maturity even in young naive puppies but they will cause reactions in older animals that have become sensitised by previous exposure, especially on the paws and elbows.

==Control==
Animals should be housed in conditions to prevent the build up of infective larvae and it is especially important that concrete runs are dry and well-maintained. Many of the anthelmintics licensed for use in dogs will clear hookworm infection (including praziquantel and pyrantel) and it is best to treat in the Spring when parasite burdens will be at their lowest.

==Zoonotic Potential==
Hookworms are able to cause a disease called [[Cutaneous Larva Migrans]] in humans.

{{Chapter}}
{{Mansonchapter
|chapterlink = http://www.mansonpublishing.co.uk/book-images/9781893441606_sample.pdf
|chaptername = Image and parasite overview
|book = Parasitology - Diagnosis and Treament of Common Parasitisms in Dogs and Cats
|author = Dwight Bowman, Elizabeth Fogarty, Stephen Charles Barr
|isbn =9781893441606
}}

{{Learning
|literature search = [http://www.cabdirect.org/search.html?q=title%3A%28%22+Uncinaria+stenocephala%22%29 ''Uncinaria stenocephala'' publications]
}}

{{OpenPages}}

[[Category:Ancylostomatoidea]][[Category:Dog_Nematodes]]

Skull and Facial Muscles - Anatomy & Physiology

2011-10-23T15:01:38Z

Vulpesferrilata:

[[Image:Deer Skull with Antlers.jpg|thumb|right|400px|'''Deer Skull with Antlers''', Nabrown, date unknown]]

== Introduction ==

The shape and size of the skull varies widely, not only between species but also with age, breed and sex of similar species. The skull is divided into three components - the '''neurocranium''', the '''dermatocranium''' and the '''viscerocranium'''. The skull also includes the '''[[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]]''', '''mandible''', '''ossicles of the middle [[Ear - Anatomy & Physiology|ear]]''' and the cartilage of the '''[[Larynx - Anatomy & Physiology|larynx]]''', '''nose''' and '''[[Ear - Anatomy & Physiology|ear]]'''. The skull protects the brain and head against injury and supports the structures of the face. In some animals the skull is also used for defensive actions, for example in [[Horn - Anatomy & Physiology|horned]] ungulates such as red deer stags. The '''neurocranium''' develops from the neural crest and mesoderm and undergoes [[Bone & Cartilage Development - Anatomy & Physiology|endochondral ossification]]. It lies ventral to the brain. The '''dermatocranium''' lies dorsal to the brain and develops from the neural crest and mesoderm. It undergoes [[Bone & Cartilage Development - Anatomy & Physiology#1._Intramembranous_Ossification|intramembranous ossification]]. The '''viscerocranium''' is the pharyngeal skeleton. It is derived only from the neural crest and undergoes endochondral and intramembranous ossification. The various facial muscles attach onto the skull in different places depending on their function. Movement of the external appendages, [[Mastication|mastication]] and facial expressions all rely on the movement of the facial muscles. 

== Structure ==

The skull is made of many small bones, most of which are paired. Cartilage or fibrous tissue separates the bones of the skull in the young animal and once growth has ceased, the sutures begin to ossify. 

== Function ==

The skull has various functions including protection of brain, support of the facial muscles by providing origin and insertion sites, development of foramen to provide entry and exit places for the vasculature and nervous system and a defense function. 

== Bones of the Skull ==

=== Occipital Bone (''os occipitale'') ===

[[Image:Pig skull dorsal.jpg|thumb|right|150px|'''Dorsal Pig skull''', nabrown, 2008]] The occipital bone forms the '''nuchal wall''' and the '''foramen magnum'''. The '''pars basilaris''' element is the caudal base of the cranium, although rostral to foramen magnum and joined by a cartilagenous suture to '''basisphenoid bone'''. It has muscular tubercules on ventral surface where the flexors of the head and neck attach and a caudocranial fossa encloses the pons and medulla oblongata. The squamous part '''''(pars squamosa)''''' is dorsal to lateral parts and occipital condyles. A nuchal crest is present and is easily palpable. The nuchal crest is often used as a landmark for collection of cerebrospinal fluid (CSF). There are also external occipital protuberances present which provide muscle attachment sites for the nuchal ligament. The lateral parts '''''(partes laterales)''''' form the borders of foramen magnum. '''Occipital condyles''' are present which articulate with the atlas to form the atlanto-occipital joint. The '''paracondylar process''' provide muscle attachment sites for muscles of the head. The '''hypoglossal canal''' is also within this structure. 

=== Sphenoid Bone (''os sphenoidale'') ===

[[Image:Pig skull ventral view.jpg|thumb|right|150px|'''Ventral Pig Skull''', nabrown, 2008]] The sphenoid bone forms the base of the neurocranium and is composed of a body and wings. The bones are separated by cartilage which ossifies with age. The '''presphenoid (''os praespenoidale'')''' is rostral and has a caudal fossa which is a hollow body with sphenoid sinuses located inside. Within the sinuses are the '''optic chiasma''' and '''optic canal'''. The '''basisphenoid (''os basispenoidalis'')''' is caudal and has a '''median cranial fossa'''. The wings oppose the temporal bone, maxilla, orbit and the brain. The wings also form the '''oval foramen''' and other foramena (see [[Skull and Facial Muscles - Anatomy & Physiology#Species_Differences|species differences]]) including the '''carotid notch, oval foramen''' and '''spinous notch''' (in the horse). The pterygoid processes are also present. 

=== Temporal Bone (''os temporale'') ===

[[Image:Zygomatic arch.jpg|thumb|right|150px|'''Pig Zygomatic Arch''', nabrown, 2008]] The temporal bone is composed of '''squamous, petrosal''' and '''tympanic''' parts and forms the lateral wall of the cranial cavity. It articulates with the frontal, parietal and sphenoid bones. The squamous element joins the temporal process of the zygomatic bone to form the '''zygomatic arch''' and forms the articulating surface of the '''[[Mastication#Jaw_Articulation|temporomandibular joint]]'''. An '''articular tubercle''' and '''mandibular fossa''' are present. Occipital process and retrotympanic processes surround the '''external acoustic meatus''' whilst the petrosal part encloses the inner ear internally via the '''internal acoustic meatus'''. Ventrally this structure forms the '''mastoid process'''. The '''styloid process''' attaches the '''[[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]]''' and a '''stylomastoid foramen''' is also present. The tympanic part is the ventral section of the temporal bone containing the '''tympanic bulla'''. The '''tympanic membrane''' separates tympanic cavity from '''external acoustic meatus''' and encloses the '''auditory ossicle''' dorsally. The musculotubal canal contains tensors of the [[Soft Palate#Musculature_and_Innervation|soft palate]]. 

=== Frontal Bone (''os frontale'') ===

The frontal bone is a paired structure joined by the '''interfrontal suture''' between the cranium and the face and enclosing the '''frontal sinuses'''. The nasal and lacrimal bones border the frontal squama section and form the zygomatic process laterally and part of the orbit dorsally. Lacrimal glands are also present near the orbit. The '''temporal line''' extends into the '''external sagittal crest'''. Ruminants also have a '''cornual process''' in [[Horn - Anatomy & Physiology|horned]] variants. The nasal section is the rostral part of the frontal bone and the orbital part is perforated by the '''ethmoidal foramen'''. Medially the '''dorsal oblique muscle''' of the eyeball attaches. The temporal part provides the muscle attachments for the '''temporalis muscle'''. 

=== Parietal Bone (''os parietale'') ===

[[Image:Pareital Bone.jpg|thumb|right|150px|'''Parietal Bone''', nabrown, 2008]] The parietal bone is a paired structure and forms the dorsolateral wall of the cranium with the cccipital bone caudally and the frontal bone rostrally. It is composed of a parietal plane, temporal plane and a nuchal plane (in the ox). Internally the grooves and ridges correspond with the gyri and sulci of the brain. There is also an '''interparietal bone''' between the occipital bone and the parietal bone which fuses with age. 

=== Ethmoid Bone (''os ethmoidale'') ===

[[Image:Nasal Cavities.jpg|thumb|right|150px|'''Nasal Cavities''', David Bainbridge]] The ethmoid bone forms part of the cranial and facial parts of the skull and is located deep in the orbit. External lamina consist of the roof plate, floor plate and paired orbital plates. The ethmoid bone is separated from the cranial cavity by the '''cribiform plate'''. Numerous small foramina exist where the '''olfactory nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN I]]) passes through. The perpendicular plate splits the ethmoid into two halves and the ethmoid larbyrinth protrudes from the ethmoid tubes. The tubes are composed of two rows of '''ethmoturbinates''' and air filled '''ethmoidal meatuses'''. Secondary ethmoturbinates may also be present. Ethmoturbinates are divided into '''endoturbinates''' and '''ectoturbinates'''. The first endoturbinate forms the dorsal nasal conchae and the second endoturbinate froms the middle nasal conchae. The endoturbinates form 3 nasal meatuses; the '''dorsal nasal meatus''', the '''middle nasal meatus''' and the '''ventral nasal meatus'''. [[Image:Ethmoid Turbinates.jpg|thumb|right|150px| '''Ethmoid Turbinates''', nabrown, 2008]] 

=== Nasal Bone (''os nasale'') ===

The nasal bone is a paired structure and forms the roof of the nasal cavity. '''Dorsal nasal conchae''' attach to the '''ethmoidal crest''' on the internal surface. A rostral suture forms the apex and between the nasal and incisive bones is the '''nasoincisive notch'''. 

=== Lacrimal Bone (''os lacrimale'') ===

The lacrimal bone forms part of the lateral wall of the face and orbit and is situated near the '''medial canthus'''. It articulates with the '''frontal bone, zygomatic bone''' and '''maxilla'''. It also articulates with the '''nasal bone''' in ruminants and the horse and articulates with the '''palatine bone''' in carnivores. It is composed of an orbital and facial part separated by supra- and infraorbital margins. The '''nasolacrimal duct''' is present by the margin of the orbital surface. The '''ventral oblique muscle''' attaches caudal to the margin of the orbital surface. The nasal surface forms the boundaries of the '''maxillary and frontal sinuses'''. 

=== Zygomatic Bone (''os zygomaticum'') ===

The zygomatic bone is lateral and ventral to the lacrimal bone and forms the orbit and zygomatic arch. The supraorbital margin is formed by the zygomatic process of the temporal bone and the frontal process of the zygomatic bone. The facial crest is present on lateral surface. 

=== Incisive Bone (''os incisivium'') ===

[[Image:Cow skull lateral view.jpg|thumb|right|150px|'''Cow skull lateral view''', nabrown, 2008]] The incisive bone is a paired structure composed of body, nasal, palatine and alveolar parts. It joins with the maxilla to form the '''interalveolar margin'''. It also forms the rostral part of the facial section of the skull, the roof of the '''[[Hard Palate|hard palate]]''' and the opening to the nasal cavity. The alveolar process forms conical sockets for the incisor teeth. 

=== Palatine Bone (''os palatinum'') ===

[[Image:Palatine Bone.jpg|thumb|right|150px|'''Palatine Bone''', nabrown, 2008]] The palatine bone is a paired structure between the maxilla, sphenoid and pterygoid bones. It is composed of a horizontal plate (forms part of the [[Hard Palate|hard palate]]), perpendicular plate (forms the dorsal and lateral walls of the nasopharyngeal meatus) and the choanae. The '''nasal crest''' present on the horizontal plate. The '''palatine sinus''' is present on horizontal plate. 

=== Vomer ===

The vomer is unpaired and extends from the choanae of the palatine bone to the floor of the nasal cavity. It attaches to the median nuchal crest and has a '''septal sulcus''' which surrounds nasal cavity. 

=== Pterygoid Bone (''os pterygoideum'') ===

The pterygoid bone is a paired structure bordered by the '''palatine''' and '''sphenoid bones'''. It forms the dorsal and lateral walls of the '''nasopharyngeal cavity'''. The '''pterygoid hamulus''' is formed by the pterygoid bone. 

=== Maxilla ===

[[Image:Horse Maxilla.jpg|thumb|right|150px|'''Horse Maxilla''', nabrown, 2008]] The maxilla forms most of the facial part of the skull, including the lateral walls of the face, nasal cavity, [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] and [[Hard Palate|hard palate]]. It also forms the ventral nasal conchae and articulates with all of the facial bones as it is the largest bone of the face. The maxillary body encloses the '''maxillary sinuses''' and forms the external surface of the face. It also forms the '''facial crest'''. The '''infraorbital foramen''' is palpable. The '''conchal crest''' is on nasal surface where the ventral nasal conchae attaches. The '''lacrimal canal''' opens into the '''lacrimal foramen''' on the nasal surface. The '''pterygopalatine surfaces''' are the caudal part of the maxilla which terminate in the '''maxillary tubercle''' where the '''sphenopalatine, maxillary''' and '''caudal palatine foramen''' are present. The '''alveolar processes''' present are separated by '''interalveolar septa'''. The '''palatine process''' forms the '''[[Hard Palate|hard palate]]''' with the palatine bone. The '''palatine fissure''' is formed at the articulation with the incisive bone. The nasal surface of palatine process forms the '''nasal crest''' and encloses part of the palatine sinuses. The oral surface has numerous palatine foramina present. 

=== Mandible (''mandibula'') ===

[[Image:Cow Mandible.jpg|thumb|right|150px|'''Cow Mandible''', nabrown, 2008]] [[Image:Parrot Mandible.jpg|thumb|right|150px|'''Parrot Mandible''', nabrown, 2008]] The mandible can be divided into the '''body''' and the '''ramus'''. The body of the mandible supports the incisor teeth (rostrally) and cheek teeth (caudally). The section of the body which does not support any teeth is called the '''interalveolar margin''' or '''diastema'''. The mandibule also contains the '''mandibular canal''' and the '''mental foramen'''. The '''facial notch''' is on the ventral surface where the '''parotid duct''' (in herbivores) and facial vessels run. The '''ramus''' extends from the caudal end of the body dorsally towards the zygomatic arch. The '''masseter muscle''' attaches to the lateral surface at the '''masseteric fossa'''. The '''medial pterygoid''' attaches to the medial surface at the '''pterygoid fossa'''. The angle of the mandible terminates dorsally in the '''condylar process''' and the '''coronoid process''' which are separated by the '''mandibular notch'''. The '''temporal muscle''' inserts onto the '''coronoid head'''. The condylar process articulates with the mandibular process of the skull (see [[Mastication#Jaw_Articulation|here]]). 

== Major Foramen and Canals ==

[[Image:Foramen Magnum.jpg|thumb|right|150px|'''Foramen Magnum''', nabrown, 2008]] The '''jugular foramen''' is located either side of basilar part of occipital bone, adjacent to tympanic bulla and contains the '''glossopharyngeal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN IX]]), '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) and '''accessory nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN XI]]). The jugular foramen also contains the '''internal carotid artery'''. The '''foramen magnum''' is formed by the occipital bones and is the spinal cord's passage to the neck and body. The '''alar ligaments''' run through the foramen magnum together with vertebral arteries, spinal arteries and tectoral membranes. The '''hypoglossal canal''' is between paracondylar and condylar processes on lateral part of occipital bone. The '''hypoglossal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN XII]]), '''condylar artery''' and '''condylar vein''' all pass through. The '''optic chiasma''' runs in a transverse depression behind the '''sphenoid rostrum''' on presphenoid bone and facilitates the path of the '''optic nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN II]]). [[Image:Sheep Skull Eye Foramen.jpg|thumb|right|150px|'''Skull Eye Foramen''', nabrown, 2008]] The '''optic canal''' passes from the '''optic chiasma''' over wings of the presphenoid bones and facilitates the path of the '''optic nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN II]]). The '''oval foramen''' is found within the caudal wing of the basisphenoid bones and the '''mandibular branch of the trigeminal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN V3]]) passes through it. The '''alar canal''' is formed by the rostral border of the basisphenoid bone at the base of the pterygoid processes. It is composed of the '''caudal alar foramen, rostral alar foramen''' and the '''small alar foramen'''. The '''maxillary branch of the trigeminal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN V2]]) passes through together with the '''temporal artery'''. [[Image:Pig Foramen Ventral.jpg|thumb|right|150px|'''Pig Ventral Skull Foramen''', nabrown, 2008]] The '''stylomastoid foramen''' is situated on the petrosal part of the temporal bone and allows the '''facial nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN VII]]) to pass through. The '''ethmoidal foramen''' perforates the orbital part of the frontal bone allowing the '''olfactory nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN I]]) and '''ethmoidal artery and vein''' to pass through. [[Image:Cow Skull dorsal view.jpg|thumb|right|150px|'''Cow Skull Dorsal View''', nabrown, 2008]] The '''orbital fissure''' is on the presphenoid bone and allows the '''opthalmic branch of the trigeminal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN V1]]), '''occulomotor nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN III]]), '''trochlear nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN IV]]) and the '''abducens nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN VI]]) to pass through. The '''supraorbital foramen''' is on the frontal bone and allows the '''opthalmic branch of the trigeminal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN V1]]) to pass through together with the '''frontal artery and vein'''. The '''infraorbital foramen''' is on the maxilla and allows the '''maxillary branch of the trigeminal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN V2]]) to pass through together with the '''infraorbital artery and vein'''. [[Image:Mental and Infraorbital Foramen.jpg|thumb|right|150px|'''Mental and Infraorbital Formen''', nabrown, 2008]] The '''mental foramen''' is on rostral end of the mandible and allows the '''mandibular branch of the trigeminal nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN V3]]) and the '''mental artery and vein''' to pass. The '''palatine canal''' runs through horizontal plate of palatine bone and allows the '''palatine artery''', '''palatine vein''' and '''palatine nerves''' to pass through. The '''internal acoustic meatus''' is made up of the medial surface of the petrosal part of the temporal bone and is the facial opening for the '''facial nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN VII]]). It is also the cochlear opening, dorsal vestibule opening and the ventral vestibule opening for the '''vestibulocochlear nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN VIII]]). 

== Facial Muscles ==

[[Image:Muscles of Mastication.jpg|thumb|right|150px|'''Muscles of Mastication''', C.Clarkson and T.F.Fletcher, date unknown]] The major facial muscles are covered in the following sections of anatomy and physiology:

[[Tongue - Anatomy & Physiology#Muscles|Muscles of the Tongue]]

[[Cheeks|Muscles of the Cheeks]]

[[Larynx - Anatomy & Physiology#Intrinsic_Musculature|Muscles of the Larynx]]

[[Pharynx - Anatomy & Physiology#Musculature|Muscles of the Pharynx]]

[[Eye - Anatomy & Physiology#Around_the_Eye|Muscles of the Eye]]

[[Ear - Anatomy & Physiology#Outer_Ear|Muscles of the Ear]]

[[Deglutition|Muscles involved in Deglutition]]

[[Mastication|Muscles of Mastication]]

== Species Differences ==

=== Canine ===

[[Image:Pug skull.jpg|thumb|right|150px|'''Brachycephalic skull''', nabrown, 2008]] Dogs have different skull lengths depending on breed. '''mesocephalic''' dogs have average conformation whilst '''dolichocephalic''' dogs have longer skull lengths and '''brachycephalic''' dogs have shorter skull lengths. The two sides of the mandible do not fuse allowing some movement in the canine jaw. The '''external sagittal crest''' arises from '''nuchal crest'''. The wings of the basisphenoid bones form the '''oval foramen, spinous foramen''' and '''carotid canal'''. Dogs have no '''foramen lacerum''' and the styloid process is absent. In canines, the dorsal orbital margin is formed by the orbital ligament, the orbit is incomplete. 

=== Feline ===

[[Image:Lion skull.jpg|thumb|right|150px|'''Lion skull''', nabrown, 2008]] The mandible appears globular in shape and the large orbits have complete bony margins. There are also large '''tympanic bullae''' which can be palpated. The two parts of the mandible do not fuse allowing some movement. Cats have a '''weak external sagittal crest''' arising from the '''nuchal crest'''. The wings of the basisphenoid bones form the '''oval foramen, spinous foramen''' and '''carotid canal'''. Cats have no '''foramen lacerum''' and the styloid process is absent. The dorsal margin of orbit is formed by the orbital ligament which is ossified. The '''interparietal bone''' does not fuse entirely in the adult. 

=== Equine ===

[[Image:Horse Skull.jpg|thumb|right|150px|'''Horse Skull''', nabrown, 2008]] Horses have a '''weak external sagittal crest''' arising from the '''nuchal crest'''. They also have an '''internal sagittal crest''' on the '''internal surface of the parietal bone'''. The orbit is placed more laterally with a complete bony rim and a strong '''zygomatic arch''' continues on to form the '''facial crest'''. There is a '''deep nasoincisive notch''' and a prominent '''hamular process'''. Horses have a very large mandible with a '''vascular notch''' and a high ramus. The wings of the basisphenoid bones form the '''oval foramen, spinous notch''' and '''carotid notch'''. Horses have a '''foramen lacerum'''. The zygomatic process articulate with the zygomatic process of the temporal bone. Horses have '''three rows of ethmoturbinates present'''. 

=== Ruminant ===

[[Image:Sheep skull.jpg|thumb|right|150px|'''Sheep skull''', nabrown, 2008]] In ruminants the skull is short and wide with a '''[[Horn - Anatomy & Physiology|cornual]]''' process on frontal bone. The nuchal crest is reduced to a '''nuchal line''', although there is a prominent '''temporal line'''. Ruminants have an elevated orbital ring which is complete but have no facial crest. There are prominent '''tympanic bullae''' and a '''nasoincisive notch''' present. The wings of the basisphenoid bones form the '''oval foramen'''. Ruminants have no '''foramen lacerum'''. The petrosal and tympanic parts of the temporal bone are fused to the squamous part. The zygomatic process articulates with the frontal process of the zygomatic bone. 

=== Porcine ===

[[Image:Pig skull.jpg|thumb|right|150px|'''Pig skull''', nabrown, 2008]] Pigs have a thick nuchal crest and an '''internal sagittal crest''' on the internal surface of the parietal bone. They have a prominent '''temporal line''' and their orbit is incomplete and small. There is a strong and deep zygomatic arch, large tympanic bullae and a high caudal part of the skull. The styloid process is absent. 

=== Avian ===

[[Image:Bird skull.jpg|thumb|right|150px|'''Bird skull''', nabrown, 2008]] Birds have '''pneumatised skull bones''' which connect to airways in the head rather than the air sacs. They have large orbits and their skull plates are separated by spongy bone. A '''single occipital condyle''' articulates with the '''atlas''' allowing more rotation of the head. In parrots, the nasal bone and frontal bone are joined by a flexible cartilage structure allowing greater jaw opening which is called the craniofacial hinge. This allows kinesis to occur. Birds have thin '''jugal arches''' (equivalent to zygomatic arch) and the middle ear contains only the columella (equivalent to the stapes). 
 
{{Learning
|flashcards= [[Skull - Musculoskeletal - Flashcards|Skull]] [[Facial Muscles - Musculoskeletal - Flashcards|Facial Muscles]]
|videos= [[Canine Lateral Head video|Potcast of the lateral surface of the canine head]]
|dragster= [[Canine Head Skeletal Anatomy Resources (I & II)]] [[Canine Head Skeletal Anatomy Resources (III, IV & V)]] [[Canine Facial Features Dissection Anatomy Resource]] [[Canine Head Radiographical Anatomy Resources (I, II & III)]] [[Canine Head Radiographical Anatomy Resources (IV & V)]] [[Equine Head Dissection Anatomy Resources (I, II & III)]] [[Equine Head Dissection Anatomy Resources (IV, V & VI)]]
}}

[[Category:Musculoskeletal_System_-_Anatomy_&_Physiology]] [[Category:A&P Done]]