Puerperium - Sow
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Also see General Puerperium
Changes of the puerperium must occur rapidly, with a return to the normal pregravid state, so that pregnancy can occur as quickly as possible after weaning.
- Rapid initial uterine shrinkage in the first 5 days postpartum.
- After day 6, most uterine weight loss is due to changes in the myometrium:
- Reduction in cell size
- Reduction in cell numbers
- Reduction in the amount of connective tissue
- Uniform decrease in thickness of the endometrium and myometrium.
- 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.
Restoration of the Endometrium
- 1 day after farrowing, the uterine epithelium is low columnar or cuboidal.
- Extensive folding present during pregnancy
- At 7 days, epithelial cells are very low and flattened, showing signs of degenerative change.
- Also signs of cell division, responsible for regeneration of the epithelium.
- Complete and capable of sustaining another pregnancy after 21 days.
Return to Ovarian Cyclicity
- Suckling and weaning have an effect on return to ovarian cyclicty (ovarian rebound) and other puerperial changes in the tract.
- 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.
- 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.
- Follicular activity occurs during suckling, which is sometimes associated with behavioural oestrus shortly after farrowing.
- No ovulation, follicles become atretic
- Preovulatory surge of LH within 7 days of 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.
- FSH concentrations rise after weaning.