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→Involution
* Uniform decrease in thickness of the endometrium and myometrium.
* Uniform decrease in thickness of the endometrium and myometrium.
* Complete by 28 days
* Complete by 28 days
* In early-weaned sows, uterine involution is slower
* The morphology and physiology of the genital tract may not be optimal for fertilization and blastocyst implantation in sows weaned at farrowing or shortly after, resulting in a reduced rate of gestation or a reduced litter size
* The fastest and most reliable way to monitor uterine involution is to use ultrasonography
* Prolonged uterine pathologies, including retention of fetal membranes or endometritis, can negatively impact the duration of uterine involution
=== Restoration of the Endometrium ===
=== Restoration of the Endometrium ===
* During puerperium the uterus returns to its nongravid size and the endometrium is restored to provide a suitable environment for the establishment of a new pregnancy
* This uterine involution is generally completed within 3 weeks of farrowing.
* 1 day after farrowing, the uterine epithelium is low columnar or cuboidal.
* 1 day after farrowing, the uterine epithelium is low columnar or cuboidal.
** Extensive folding present during pregnancy
** Extensive folding present during pregnancy
** Also signs of cell division, responsible for regeneration of the epithelium.
** Also signs of cell division, responsible for regeneration of the epithelium.
* Complete and capable of sustaining another pregnancy after 21 days.
* Complete and capable of sustaining another pregnancy after 21 days.
* An delayed restoration of endometrium and uterine involution can have a negative effect on sow reproduction.
=== Return to Ovarian Cyclicity ===
=== Return to Ovarian Cyclicity ===
* Mostly no return to oestrus and no ovulation until piglets are removed.
* Mostly no return to oestrus and no ovulation until piglets are removed.
* Time to first ovulation can be shortened by temporary removal of the whole litter for varying periods during the day (partial weaning), or permanent removal of part of the litter.
* Time to first ovulation can be shortened by temporary removal of the whole litter for varying periods during the day (partial weaning), or permanent removal of part of the litter.
* Weaning pigs immediately after farrowing or within three weeks of delivery results in higher incidence of anestrus and a longer weaning-to-estrus interval, ovulation failure, or a reduced litter size
* Female pigs that fail to ovulate either show follicular regression or develop cystic ovarian diseases.
* Rapid regression of corpora lutea of pregnancy, with cellular degeneration occuring by 3 days postpartum.
* Rapid regression of corpora lutea of pregnancy, with cellular degeneration occuring by 3 days postpartum.
* By day 7 postpartum, corpora lutea are mainly connective tissue.
* By day 7 postpartum, corpora lutea are mainly connective tissue.
** No ovulation, follicles become atretic
** No ovulation, follicles become atretic
* Preovulatory surge of LH within 7 days of weaning.
* Preovulatory surge of LH within 7 days of weaning.
* Anoestrus and ovarian cysts in early weaned pigs may be due to the lack of a preovulatory LH surge
* Most of the sows resume cyclicity within a normal weaning-to-oestrus interval of less than 7 days if they are weaned after 3 weeks of farrowing
* Prolactin concentrations are high during lactation but decline rapidly to basal levels within hours after weaning.
* Prolactin concentrations are high during lactation but decline rapidly to basal levels within hours after weaning.
* Follicular growth and ovulation are supressed during lactation due to supressed LH secretion.
* Follicular growth and ovulation are supressed during lactation due to supressed LH secretion.
[[Category:Pregnancy and Parturition]][[Category:Pig]]
[[Category:Pregnancy and Parturition]][[Category:Pig - Reproductive System]]
[[Category:Bullet Points]]