@article{belstra_flowers_croom_degroot_see_2005, title={Urinary excretion of collagen degradation markers by sows during postpartum uterine involution}, volume={85}, ISSN={["1873-2232"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-8844250111&partnerID=MN8TOARS}, DOI={10.1016/j.anireprosci.2004.04.035}, abstractNote={Incomplete uterine involution is the putative cause of the increased embryo mortality and reproductive failure often exhibited by sows that lactate for less than 21 days. Since such short lactation lengths are common in American swine production, an effective technique to monitor the postpartum involution process and test this hypothesis might be valuable. Rapid and extensive catabolism of uterine collagen is essential for normal postpartum involution. The objective of this study was to characterize postpartum excretion of two biochemical markers of collagen degradation. In experiment I, urine samples were collected from five sows every other day from the day before parturition (day −1), through a 21-day lactation, to day 8 postweaning. The collagen crosslinks hydroxylysyl pyridinoline (HP), which is present in many tissues, and lysyl pyridinoline (LP), which is primarily concentrated in bone, were assayed by both ELISA and HPLC. Urinary levels of both free (ELISA) and total (HPLC) HP and LP increased (P < 0.001) approximately two-fold during lactation. The mean molar ratio of total HP:LP increased (P < 0.001) from 6.6 ± 1.6 at day 1 to a maximum of 10.2 ± 1.5 at day 7 postpartum and averaged 9.1 ± 0.3 for the entire sampling period. These data are consistent with a postpartum increase of soft tissue collagen catabolism since bone has a low HP:LP ratio of 4 and soft tissues like the uterus have a high HP:LP ratio of ≥20 because they contain only trace amounts of LP. Since HPLC (total) and ELISA (free) crosslinks estimates were highly correlated (r = 0.85–0.91, P < 0.001) in experiment I, only the less technical ELISA technique was used in experiment II. Urine samples were collected from 21 sows every third day from day 1 to 19 of lactation. Sows from this second group exhibited one of four distinct crosslinks excretion patterns: peak on day 1 (n = 3), peak on day 7 (n = 4), peak on day 10, 13 or 16 (n = 7), or no peak (n = 7). This variation of postpartum crosslinks excretion among sows was not related to parity, body weight, lactation body weight change, litter size, or litter birth weight. Overall, data from experiments I and II indicate that urinary HP does increase postpartum in a pattern temporally consistent with uterine involution. However, significant variation among sows in the magnitude and timing of peak HP excretion was evident.}, number={1-2}, journal={ANIMAL REPRODUCTION SCIENCE}, author={Belstra, BA and Flowers, WL and Croom, WJ and DeGroot, J and See, MT}, year={2005}, month={Jan}, pages={131–145} }
 @article{belstra_flowers_see_2004, title={Factors affecting temporal relationships between estrus and ovulation in commercial sow farms}, volume={84}, ISSN={["1873-2232"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-4143080539&partnerID=MN8TOARS}, DOI={10.1016/j.anireprosci.2004.02.005}, abstractNote={The main objective was to examine effects of season, parity, genotype, lactation length, and weaning-to-estrus interval on duration of estrus (DE) and onset of estrus-to-ovulation interval (EOI) in three sow farms. Detection of estrus and ovulation by the back-pressure test and transabdominal ultrasonography, respectively, were performed every 6 h from day 2–10 postweaning in 535 sows (approximately 89 per farm per season). The average weaning-to-estrus interval, DE, and EOI of the 501 sows that returned to estrus by day 10 postweaning were 4.6±0.1 days, 55.2±0.5 h, and 41.8±0.5 h, respectively. Farm × season (P<0.01), parity×season (P<0.05), and farm×weaning-to-estrus interval (P<0.05) interactions for DE and EOI were detected. Sows weaned in the summer had an 8 h longer (P<0.001) DE and EOI than those weaned in the spring on farms 1 and 3. On farm 2 however, DE and EOI did not differ (P=0.09) in sows weaned in summer versus spring. On each farm, parity 3 and ≥4 sows had a 4.5 h longer (P<0.05) DE and EOI than parity 1 and 2 sows in the summer, but there were no differences (P>0.11) in DE or EOI among parity classes in the spring. There was a linear decrease of DE (P<0.001) and EOI (P<0.05) as weaning-to-estrus interval increased from the 3 to the ≥7 day class on each farm. However, the range of weaning-to-estrus interval that exhibited a stepwise decrease of DE and EOI was narrower on farm 1 (3–5 days) than farms 2 and 3 (3–6 days). Only farms 1 and 3 had multiple genotypes. Genotype did not affect (P>0.14) DE on either farm, but the EOI of genotype B was 4 h shorter (P<0.05) than genotype C on farm 1. On each farm, DE decreased linearly (P<0.01) as lactation length increased from ≤13 to ≥20 days. In general, factors that affected EOI also affected (P<0.05) the percentage of inseminations that occurred within 24 h pre- to 3 h post-ovulation. These data 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 weaning-to-estrus interval on DE and EOI can be inconsistent among different farms.}, number={3-4}, journal={ANIMAL REPRODUCTION SCIENCE}, author={Belstra, BA and Flowers, WL and See, MT}, year={2004}, month={Sep}, pages={377–394} }