Changes

== Photoperiod ==

== Photoperiod ==

The month of birth will influence the onset of puberty, especially in [[Female_Reproductive_Tract_-Seasonality_of_Reproduction_-_Anatomy_%26_Physiology|seasonal breeders]].

The month of birth will influence the onset of puberty, especially in [[Female_Reproductive_Tract_-Seasonality_of_Reproduction_- Anatomy & Physiology|seasonal breeders]].

=== Sheep ===

=== Sheep ===

* [[Female_Reproductive_Tract_-Seasonality_of_Reproduction_-_Anatomy_%26_Physiology|Short day breeders]] (begin oestrous cycles in response to short day length)

* [[Female_Reproductive_Tract_-Seasonality_of_Reproduction_- Anatomy & Physiology|Short day breeders]] (begin oestrous cycles in response to short day length)

* Spring born lambs (February-March) reach puberty in the subsequent autumn (September-October) if they have adequate nutrition.  The age at puberty is 5-6 months.

* Spring born lambs (February-March) reach puberty in the subsequent autumn (September-October) if they have adequate nutrition.  The age at puberty is 5-6 months.

* Autumn born lambs do not reach puberty until 10-12 moths of age.  

* Autumn born lambs do not reach puberty until 10-12 moths of age.  

* This is because, seasonal cues (long days of spring/summer) delay reproductive cyclicity.

* This is because, seasonal cues (long days of spring/summer) delay reproductive cyclicity.

* Thus, [[Reproductive_Behaviour_-_Oestrus_Behaviour_-_Anatomy_%26_Physiology|oestrus]] in both spring and autumn born lambs is synchronised.

* Thus, [[Reproductive_Behaviour_-_Oestrus_Behaviour_- Anatomy & Physiology|oestrus]] in both spring and autumn born lambs is synchronised.

* This maximizes the chance that all ewes become pregnant in the fall and give birth in the spring when nutritional and environmental conditions are favourable.

* This maximizes the chance that all ewes become pregnant in the fall and give birth in the spring when nutritional and environmental conditions are favourable.

* An adequate degree of nutrition ('fatness') is required before photoperiod can exert an effect.

* An adequate degree of nutrition ('fatness') is required before photoperiod can exert an effect.

=== Queen ===

=== Queen ===

* [[Female_Reproductive_Tract_-Seasonality_of_Reproduction_-_Anatomy_%26_Physiology|Long day breeders]]

* [[Female_Reproductive_Tract_-Seasonality_of_Reproduction_- Anatomy & Physiology|Long day breeders]]

* Increasing photoperiod prompts onset of puberty.

* Increasing photoperiod prompts onset of puberty.

* Onset of puberty occurs in January-February in the Northern Hemisphere, where there is increasing day length.

* Onset of puberty occurs in January-February in the Northern Hemisphere, where there is increasing day length.

* Queens born in February-March do not reach puberty until the following spring.

* Queens born in February-March do not reach puberty until the following spring.

* Queens born in summer/autumn generally display their first [[Reproductive_Behaviour_-_Oestrus_Behaviour_-_Anatomy_%26_Physiology|oestrus]] the following January.

* Queens born in summer/autumn generally display their first [[Reproductive_Behaviour_-_Oestrus_Behaviour_- Anatomy & Physiology|oestrus]] the following January.

* Before this can have effect, there must be adequate nutrition and growth.

* Before this can have effect, there must be adequate nutrition and growth.

== Environmental and Social Conditions ==

== Environmental and Social Conditions ==

* [[Reproductive_Behaviour_-_Attractivity_Behaviour_-_Anatomy_%26_Physiology#Pheromones|Pheromonal]] substances in the [[Normal_Composition_of_Urine_-_Anatomy_%26_Physiology|urine]] act as a stimulus to enhance the onset of puberty.

* [[Reproductive_Behaviour_-_Attractivity_Behaviour_- Anatomy & Physiology#Pheromones|Pheromonal]] substances in the [[Normal_Composition_of_Urine_- Anatomy & Physiology|urine]] act as a stimulus to enhance the onset of puberty.

* Females reaching puberty in the presence of a male (producing the pheromones) have a greater opportunity of becoming pregnant.

* Females reaching puberty in the presence of a male (producing the pheromones) have a greater opportunity of becoming pregnant.

* Pubertal onset cannot be accelerated using [[Reproductive_Behaviour_-_Attractivity_Behaviour_-_Anatomy_%26_Physiology#Pheromones|pheromones]] in animals that have not achieved the appropriate metabolic body size to trigger [[Hypothalamus_-_Anatomy_%26_Physiology|hypothalamic]] responsiveness to Oestradiol (oestrogen).

* Pubertal onset cannot be accelerated using [[Reproductive_Behaviour_-_Attractivity_Behaviour_- Anatomy & Physiology#Pheromones|pheromones]] in animals that have not achieved the appropriate metabolic body size to trigger [[Hypothalamus_- Anatomy & Physiology|hypothalamic]] responsiveness to Oestradiol (oestrogen).

* [[Eye - Anatomy & Physiology|Visual]] and [[Nose - Anatomy & Physiology|olfactory]] environmental information is perceived by sensory neurons of the optic and [[Nose - Anatomy & Physiology|olfactory]] systems.

* [[Eye - Anatomy & Physiology|Visual]] and [[Nose - Anatomy & Physiology|olfactory]] environmental information is perceived by sensory neurons of the optic and [[Nose - Anatomy & Physiology|olfactory]] systems.

* Stimuli are processed by the [[Nervous and Special Senses - Anatomy & Physiology#Central Nervous System (CNS)|central nervous system]] and converted into neural inputs to the GnRH neurons of the [[Hypothalamus_-_Anatomy_%26_Physiology|hypothalamus]].

* Stimuli are processed by the [[Nervous and Special Senses - Anatomy & Physiology#Central Nervous System (CNS)|central nervous system]] and converted into neural inputs to the GnRH neurons of the [[Hypothalamus_- Anatomy & Physiology|hypothalamus]].

* The [[Hypothalamus_-_Anatomy_%26_Physiology|hypothalamus]] then gains the ability to produce high frequency and high amplitude pulses of GnRH at an earlier age.

* The [[Hypothalamus_- Anatomy & Physiology|hypothalamus]] then gains the ability to produce high frequency and high amplitude pulses of GnRH at an earlier age.

[[Category:Reproductive System]]

[[Category:Reproductive System]]