Stevenson J S, Pursley J R, Garverick H A, Fricke P M, Kesler D J, Ottobre J S, Wiltbank M C
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-0201, USA.
J Dairy Sci. 2006 Jul;89(7):2567-78. doi: 10.3168/jds.S0022-0302(06)72333-5.
Our objective was to determine whether progesterone (P4) supplementation during an Ovsynch protocol would enhance fertility in lactating dairy cows. Lactating dairy cows (n = 634) at 6 locations were assigned randomly within lactation number and stage of lactation to receive the Ovsynch protocol [OVS; synchronization of ovulation by injecting GnRH 7 d before and 48 h after PGF(2alpha), followed by one fixed-time AI (TAI) 16 to 20 h after the second GnRH injection] or Ovsynch plus a controlled internal drug release (CIDR) P4-releasing insert for 7 d, beginning at the first GnRH injection (OVS + CIDR). Blood was sampled to quantify P4 10 d before the first GnRH injection, immediately before the first GnRH injection, at the time of CIDR removal, before the PGF(2alpha) injection (1 to 2 h after CIDR insert removal), and 48 h after the PGF(2alpha) injection to determine cyclicity status before initiation of treatment, luteal status at the PGF(2alpha) injection, and incidence of luteal regression. Overall, conception rates at 28 (40 vs. 50%) and 56 d (33 vs. 38%) after TAI differed between OVS and OVS + CIDR, respectively; but a treatment x location interaction was detected. Compared with OVS, pregnancy outcomes were more positive for OVS + CIDR cows at 4 of 6 locations 28 d after TAI and at 3 of 6 locations 56 d after TAI. An interaction of luteal status (high vs. low) before CIDR insert removal and PGF(2alpha) injection with pretreatment cycling status indicated that cows having low P4 at PGF(2alpha) injection benefited most from P4 supplementation (OVS + CIDR = 36% vs. OVS = 18%), regardless of pretreatment cycling status. Pregnancy loss between 28 and 56 d after TAI was greater for noncycling cows (31%) compared with cycling cows (16%). Pregnancy loss for cows receiving P4 (21%) did not differ from that for cows not receiving P4 (21%). Supplementation of P4, pretreatment cycling status, and luteal status before PGF(2alpha) injection altered follicular diameters at the time of the second GnRH injection, but were unrelated to pregnancy outcomes. Incidence of multiple ovulation was greater in noncycling than in cycling cows. Further, cows having multiple ovulations had improved pregnancy outcomes at 28 and 56 d after TAI. In summary, a CIDR insert during the Ovsynch protocol increased fertility in lactating cows having low serum P4 before PGF(2alpha) injection. Improved pregnancy outcomes were observed at some, but not all locations.
我们的目标是确定在Ovsynch方案期间补充孕酮（P4）是否会提高泌乳奶牛的繁殖力。在6个地点的634头泌乳奶牛，根据泌乳次数和泌乳阶段随机分组，接受Ovsynch方案[OVS；通过在PGF（2α）注射前7天和注射后48小时注射GnRH来同步排卵，然后在第二次GnRH注射后16至20小时进行一次定时人工授精（TAI）]或从第一次GnRH注射开始，Ovsynch方案加一个持续释放P4的可控内部药物释放（CIDR）插入物7天（OVS + CIDR）。在第一次GnRH注射前10天、第一次GnRH注射前即刻、去除CIDR时、PGF（2α）注射前（去除CIDR插入物后1至2小时）以及PGF（2α）注射后48小时采集血样，以确定治疗开始前的周期性状态、PGF（2α）注射时的黄体状态以及黄体退化的发生率。总体而言，TAI后28天（40%对50%）和56天（33%对38%）的受孕率在OVS和OVS + CIDR之间分别有所不同；但检测到治疗×地点的交互作用。与OVS相比，TAI后28天在6个地点中的4个地点以及TAI后56天在6个地点中的3个地点，接受OVS + CIDR的奶牛的妊娠结局更理想。在去除CIDR插入物和PGF（2α）注射前的黄体状态（高对低）与预处理周期状态的交互作用表明，无论预处理周期状态如何，在PGF（（2α）注射时P4水平低的奶牛从补充P4中获益最大（OVS + CIDR = 36%对OVS = 18%）。与有周期的奶牛（16%）相比，无周期的奶牛在TAI后28至56天的妊娠损失更大（31%）。接受P4的奶牛的妊娠损失（21%）与未接受P4的奶牛的妊娠损失（21%）没有差异。在第二次GnRH注射时，补充P4、预处理周期状态以及PGF（2α）注射前的黄体状态改变了卵泡直径，但与妊娠结局无关。无周期的奶牛的多排卵发生率高于有周期的奶牛。此外，有多排卵的奶牛在TAI后28天和56天的妊娠结局有所改善。总之，在Ovsynch方案期间使用CIDR插入物可提高在PGF（2α）注射前血清P4水平低的泌乳奶牛的繁殖力。在一些但并非所有地点观察到了改善的妊娠结局。
