Studies on improving the fertility of aged sows. 3. Results of histological studies on puerperal involution and regeneration processes in the endometrium of lactating sows and sows after extremely early weaning]

Involution and regeneration following parturition was studied in 48 sows allowed to suckle their piglets normally, or from which the piglets were taken away at 5-8 days of age. Samples of uterus were obtained by biopsy 4, 8, 11, 14, 17, 20, 30, 32 and 40 days after parturition. In lactating sows, endometrial changes similar to those of oestrus in a normal cycle were present 32 days after parturition. This fact seems to justify the removal of piglets at 21-28 days of age. After very early weaning (5-8 days), incomplete oestrus-like changes in the endometrium were seen on the 17th day after parturition. The observed involutionary and regenerative changes in the puerperal uterus suggest that early weaning after 10-12 days of suckling is feasible, but it may be advisable to use drugs that would accelerate uterine involution.