Santos J E P, Rutigliano H M, Sá Filho M F
Department of Animal Sciences, University of Florida, Gainesville, FL 32611-0920, United States.
Anim Reprod Sci. 2009 Feb;110(3-4):207-21. doi: 10.1016/j.anireprosci.2008.01.014. Epub 2008 Jan 20.
The objectives of this study were to evaluate factors associated with resumption of postpartum estrous cycles and embryonic survival in lactating dairy cows. Holstein cows, 6396 from four dairy farms were evaluated to determine the relationships among parity, body condition score (BCS) at calving and at AI, season of year when cows calved, and milk yield on resumption of postpartum estrous cycles by 65 days postpartum, and all the previous variables, estrual or anestrus and AI protocol on conception rates and embryonic survival at the first postpartum insemination. Cows had their estrous cycle pre-synchronized with two PGF(2alpha) injections given 14 days apart and were inseminated between 69 and 82 days postpartum following either an estrous or ovulation synchronization protocol initiated 12-14 days after the presynchronization. Blood was sampled and analyzed for progesterone twice, 12-14 days apart, to determine whether cows had initiated onset of estrous cycles after calving. Cows were scored for body condition in the week after calving, and again at AI, between 69 and 82 days postpartum. Pregnancy was diagnosed at 30+/-3 and 58+/-3 days after AI. Farm influenced all reproductive outcomes evaluated. More (P<0.0001) multiparous than primiparous cows had initiated estrous cycles. Onset of estrous cycles was also influenced (P<0.01) by BCS at calving and at AI, BCS change, season, and milk yield. More (P<0.001) cows that had initiated estrous cycles than anestrous cows were pregnant at 30 and 58 days after AI, but anestrus did not affect pregnancy loss. Conception rates were also influenced (P<0.01) by parity, BCS at calving and AI, BCS change, and season; however, milk yield and insemination protocol were not associated with conception rates at 30 and 58 days after AI. Factors that reduced conception rate on day 30 after AI also increased pregnancy loss between 30 and 58 days of gestation. Improving BCS at calving and AI, minimizing losses of BCS after calving, and hastening onset of estrous cycles early postpartum are all expected to increase conception because of enhanced embryonic survival.
本研究的目的是评估与泌乳奶牛产后发情周期恢复及胚胎存活相关的因素。对来自四个奶牛场的6396头荷斯坦奶牛进行评估，以确定胎次、产犊时及人工授精时的体况评分（BCS）、奶牛产犊的年份季节以及产后65天内产后发情周期恢复时的产奶量之间的关系，以及所有先前变量、发情或乏情状态和人工授精方案对首次产后人工授精时的受孕率和胚胎存活的影响。奶牛在间隔14天注射两次前列腺素F2α（PGF2α）后进行发情周期预同步，并在预同步后12 - 14天开始的发情或排卵同步方案之后，于产后69至82天进行人工授精。每隔12 - 14天采集两次血液样本并分析孕酮，以确定奶牛产后是否开始发情周期。在产后一周内以及产后69至82天人工授精时对奶牛的体况进行评分。在人工授精后30±3天和58±3天诊断妊娠情况。农场对所有评估的繁殖结果均有影响。经产奶牛比初产奶牛更早开始发情周期（P<0.0001）。产犊时及人工授精时的BCS、BCS变化、季节和产奶量也对发情周期的开始有影响（P<0.01）。在人工授精后30天和58天，开始发情周期的奶牛比处于乏情状态的奶牛怀孕的更多（P<0.001），但乏情并不影响妊娠丢失情况。受孕率也受到胎次、产犊时及人工授精时的BCS、BCS变化和季节的影响（P<0.01）；然而，产奶量和人工授精方案与人工授精后30天和58天的受孕率无关。在人工授精后第３０天降低受孕率的因素也会增加妊娠30至58天之间的妊娠丢失。由于胚胎存活率提高，预计在产犊时及人工授精时改善BCS、尽量减少产犊后BCS的损失以及在产后早期加速发情周期的开始均会提高受孕率。
