Investigations of postpartum and postweaning factors that may affect subsequent sow reproductive performance

by 1973- Belstra, Bradley Aaron

BELSTRA, BRADLEY AARON. Investigations of postpartum and postweaning factors that may affect subsequent sow reproductive performance (Under the direction of Dr. William L. Flowers and Dr. M. Todd See). Experiment one examined effects of season, parity, genotype, lactation length, and weaning-to-estrus interval on the postweaning duration of estrus (DE) and onset of estrus-toovulation interval (EOI) of sows in three farms. Farm × weaning-to-estrus interval, farm × season, and parity × season interactions for DE and EOI were detected. Weaning-to-estrus interval had an inverse relationship with DE and EOI on each farm, but the weaning-to-estrus interval range that exhibited a stepwise decrease of DE and EOI was narrower on farm 1 (3 to 5 days) than farms 2 and 3 (3 to 6 days). Both DE and EOI were 8 h longer in the summer than the spring on farms 1 and 3, but did not differ between seasons on farm 2. On each farm, parity ? 3 sows had a 4.5 h longer DE and EOI than parity 1 and 2 sows in the summer, but there were no differences in DE or EOI among parity classes in the spring. Lactation length and genotype had small but significant effects on DE and EOI, respectively. Results of this experiment indicate that factors other than weaning-to-estrus interval, such as season and parity, can significantly alter DE and EOI. However, the effects of season and weaningto-estrus interval on DE and EOI are apparently farm dependent. Experiment two characterized the urinary excretion of two markers of collagen degradation, hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP), by sows during postpartum uterine involution. A postpartum increase of HP excretion occurred that was temporally consistent with the known pattern of uterine weight loss during involution. The mean molar ratio of HP:LP increased postpartum and confirmed that catabolism of a soft, non-bone tissue dominates this period. Experiment three investigated the use of transabdominal ultrasonography to estimate uterine size. The distance between the abdominal wall and intestines, which sandwich the uterus, decreased 8.7 cm from day 1 to 18 postpartum. Validation of these two techniques to monitor postpartum uterine involution by comparison to postmortem uterine measurements could provide a research tool to test the effects of uterine involution status on subsequent embryo survival and sow reproductive performance. ii