POSTWEANING CHANGES IN THE REPRODUCTIVE TRACT OF THE SOW

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Abstract
The postweaning growth changes in the reproductive tract of the sow were determined in 98 Yorkshire sows slaughtered at 2-day intervals from weaning (day 0) to day 16 postweaning. At the time of weaning, after a 42-day lactation, the reproductive tract resembled that of a prepubertal gilt or anestrous sow. From weaning to day 6 (estrus), the only observed change in the ovaries was an increase in size of the vesicular follicles. After ovulation there was a decrease (P < 0.01) in ovarian weight (day 6, 8.2 ± 0.3 g; day 8, 6.0 ± 0.5 g). Subsequently ovarian weight increased with development of the corpora lutea (day 16, 13.2 ± 0.9 g). Growth of the oviducts and cervix followed the pattern of ovarian follicle growth with an increase (P < 0.01) in weight and length until day 6 postweaning (7.5 ± 0.6 g, 51.7 ± 2.2 cm, and 108 ± 7 g, 15.9 ± 0.9 cm, respectively). After ovulation, the weight and length of the oviducts and the cervix declined to those observed on day 2 postweaning. Uterine weight increased (P < 0.01) from weaning to day 6 postweaning (137 ± 24 g to 371 ± 24 g). A small increase (P < 0.01) in length was observed by day 4 postweaning (125 ± 8 cm to 151 ± 5 cm). After ovulation, uterine weight decreased to 278 ± 15 g by day 8 postweaning. Subsequently both weight and length increased to day 16 postweaning (455 ± 31 g, 264 ± 11 cm). Thus, while growth of the oviducts, uterus and cervix were associated with preovulatory follicular development only uterine growth was postiviely associated with development of the corpora lutea. Key words: Sow, postweaning, reproductive tract growth