Chebel R C, Santos J E P, Cerri R L A, Rutigliano H M, Bruno R G S
Veterinary Medicine Teaching and Research Center, University of California-Davis, Tulare 93274, USA.
J Dairy Sci. 2006 Nov;89(11):4205-19. doi: 10.3168/jds.S0022-0302(06)72466-3.
The objectives of this study were to evaluate the effects of an intravaginal insert containing progesterone (CIDR, controlled internal drug releasing) administered in presynchronization and resynchronization protocols on cyclicity, detection of estrus, pregnancy rate, and pregnancy loss to first AI; reinsemination patterns; and pregnancy rates to second postpartum AI before and after the time of first-service pregnancy diagnosis in dairy cows. Holstein cows (n = 1,052) were blocked by parity and BCS at 3 +/- 3 d in milk (study d 0 = day of calving) and assigned randomly to 1 of 3 presynchronization treatments. During the presynchronization programs, all cows received 2 injections of PGF2alpha, on study d 35 and 49. Cows enrolled in the control presynchronization treatment received AI after detected estrus from study d 49 to 62. Cows enrolled in the CIDR estrus-detection (CED) presynchronization treatment received a CIDR insert from study d 42 to 49 and AI on detection of estrus from d 49 to 62. Cows enrolled in the CIDR timed AI (CTAI) presynchronization treatment received the same treatment as CED, but were subjected to timed AI on study d 72 after the Ovsynch (GnRH, 7 d PGF2alpha, 2 d GnRH, 24 h timed AI) protocol. The control and CED cows not inseminated by study d 62 were enrolled in the Ovsynch protocol on the same day and received timed AI on study d 72. After first AI, cows were assigned to no resynchronization (RCON) or resynchronization with a CIDR insert (RCIDR) between 14 and 21 d after AI. Blood samples collected on study d 35, 49, and 62 were analyzed for concentrations of progesterone and cows were classified as anestrous when progesterone was < 1.0 ng/mL in the first 2 samples. On study d 62, anestrous cows with progesterone > or = 1.0 ng/mL were classified as having resumed cyclicity. Pregnancy was diagnosed at 31 and 60 d after first AI and at 42 d after second AI. A greater proportion of anestrous cows in CED and CTAI became cyclic by d 62 postpartum than control cows. Resynchronization with the CIDR insert increased the pregnancy rate at 31 d after first AI in CED and CTAI, and at 60 d after AI in all cows because of reduced pregnancy loss. These results indicate that presynchronization with the CIDR insert increased induction of cyclicity in anestrous cows and that resynchronization with the CIDR insert did not affect the reinsemination rate but did reduce pregnancy loss and increased the pregnancy rate at 60 d after first AI.
本研究的目的是评估在预同步和再同步方案中使用含孕酮的阴道内植入物（CIDR，可控内部药物释放装置）对奶牛发情周期、发情检测、妊娠率、首次人工授精后的妊娠损失；再输精模式；以及首次配种妊娠诊断前后第二次产后人工授精的妊娠率的影响。将荷斯坦奶牛（n = 1052）在产奶3±3天（研究第0天 = 产犊日）时按胎次和体况评分进行分组，并随机分配到3种预同步处理中的1种。在预同步程序期间，所有奶牛在研究第35天和49天接受2次PGF2α注射。纳入对照预同步处理的奶牛在研究第49天至62天检测到发情后进行人工授精。纳入CIDR发情检测（CED）预同步处理的奶牛在研究第42天至49天接受CIDR植入物，并在第49天至62天检测到发情时进行人工授精。纳入CIDR定时人工授精（CTAI）预同步处理的奶牛接受与CED相同的处理，但在Ovsynch（促性腺激素释放激素、7天PGF2α、2天促性腺激素释放激素、24小时定时人工授精）方案后的研究第72天进行定时人工授精。在研究第62天未进行人工授精的对照和CED奶牛在同一天纳入Ovsynch方案，并在研究第72天接受定时人工授精。首次人工授精后，奶牛被分配到不进行再同步（RCON）或在人工授精后14至21天使用CIDR植入物进行再同步（RCIDR）。对在研究第35天、49天和62天采集的血样进行孕酮浓度分析，当在前两个样本中孕酮<1.0 ng/mL时，奶牛被分类为乏情。在研究第62天，孕酮≥1.0 ng/mL的乏情奶牛被分类为已恢复发情周期。在首次人工授精后31天和60天以及第二次人工授精后42天诊断妊娠。与对照奶牛相比，CED和CTAI中更大比例的乏情奶牛在产后第62天恢复发情周期。使用CIDR植入物进行再同步提高了CED和CTAI中首次人工授精后31天以及所有奶牛人工授精后60天的妊娠率，原因是妊娠损失减少。这些结果表明，使用CIDR植入物进行预同步增加了乏情奶牛发情周期的诱导，并且使用CIDR植入物进行再同步不影响再输精率，但确实减少了妊娠损失并提高了首次人工授精后60天的妊娠率。
