School of Veterinary Medicine, University of California, Davis CA 95616, USA.
J Dairy Sci. 2013 Mar;96(3):1612-22. doi: 10.3168/jds.2012-5971. Epub 2013 Jan 26.
The objectives of the current experiment were to evaluate the reproductive performance and economic outcome of 3 synchronization strategies for first artificial insemination (AI) of dairy heifers. Holstein heifers from 2 herds (site A, California, n=415; site B, Idaho, n=425) were assigned to 1 of 3 treatments. Heifers assigned to the AI on estrus (AIE) treatment received an injection of 25mg of PGF(2α) at enrollment (d 0) and every 11 d thereafter until AI occurred. Heifers assigned to the CIDR5 treatment received a controlled internal drug release insert (CIDR) containing 1.38 g of progesterone, which was removed 5 d later concomitantly with an injection of 25mg of PGF(2α), and received fixed-time AI (TAI) concomitantly with an injection of 100 μg of GnRH 53 to 60 h later. Heifers assigned to the CIDR7 treatment received a CIDR insert, which was removed 7 d later concomitantly with an injection of 25mg of PGF(2α), and received TAI concomitantly with an injection of 100 μg of GnRH 53 to 60 h later. Heifers were observed for estrus and inseminated up to 98 and 73 d after enrollment in sites A and B, respectively. Thereafter, heifers were moved to pens with bulls and considered failure to conceive to AI if still not pregnant at the end of the observation period. Economic outcomes were based on cost of synchronization protocol (CIDR treatment=$11, PGF(2α) or GnRH treatments=$2.5/treatment, estrous detection=$0.80/heifer per day), rearing cost ($2.75/heifer per day), and economic loss if a heifer did not conceive to first AI ($150). Input cost of the reproductive programs=synchronization protocol cost + semen cost + rearing cost + replacement cost. Pregnancy per AI (P/AI) 38 ± 3 d after first AI was greatest for AIE heifers (61.1%) followed by CIDR5 (44.8%) and CIDR7 (35.7%) heifers. Furthermore, P/AI 73 ± 7 d after first AI was greatest for AIE (58.8%) and tended to be greater for CIDR5 (42%) than for CIDR7 (34.1%) heifers. The percentage of heifers that had spontaneous luteolysis from CIDR insertion to CIDR removal was reduced for CIDR5 compared with CIDR7 (13.8 vs 31.8%). Pregnancy rate was greatest for AIE heifers but did not differ between CIDR5 [adjusted hazard ratio (95% confidence interval)=0.75 (0.63, 0.90)] and CIDR7 [adjusted hazard ratio (95% confidence interval)=0.65 (0.54, 0.77)] heifers. Consequently, rearing cost and input cost of AIE heifers ($67.1 ± 4.4 and -$107.1 ± 7.0, respectively) were reduced compared with CIDR5 ($86.9 ± 5.1 and -$143.4 ± 8.1, respectively) and CIDR7 ($98.3 ± 5.1 and -$156.5 ± 8.2, respectively) heifers, but no differences were observed between CIDR5 and CIDR7 heifers.
本实验的目的是评估 3 种首次人工授精（AI）奶牛同步方案的繁殖性能和经济结果。来自 2 个牛场（A 牛场，加利福尼亚州；B 牛场，爱达荷州）的荷斯坦小母牛被分配到 3 种处理之一。被分配到发情期 AI（AIE）处理的小母牛在登记（d0）时注射 25mg 的 PGF(2α)，此后每 11 天注射一次，直到 AI 发生。被分配到 CIDR5 处理的小母牛接受含有 1.38g 孕酮的控释宫内节育器（CIDR），5 天后取出，同时注射 25mg PGF(2α)，并在 53 至 60 小时后进行固定时间 AI（TAI）。被分配到 CIDR7 处理的小母牛接受 CIDR 插入，7 天后取出，同时注射 25mg PGF(2α)，并在 53 至 60 小时后进行 TAI。小母牛在 A 牛场和 B 牛场分别登记后 98 天和 73 天观察发情并进行授精。此后，小母牛被转移到公牛圈，如果在观察期结束时仍未怀孕，则被认为首次 AI 未受孕。经济结果基于同步方案成本（CIDR 处理$11，PGF(2α)或 GnRH 处理$2.5/处理，发情检测$0.80/小母牛每天）、饲养成本（$2.75/小母牛每天）以及如果小母牛未受孕至首次 AI 的经济损失（$150）。生殖计划的投入成本=同步方案成本+精液成本+饲养成本+替代成本。首次 AI 后 38±3 天的妊娠率（P/AI）以发情期 AI（61.1%）的小母牛最高，其次是 CIDR5（44.8%）和 CIDR7（35.7%）的小母牛。此外，首次 AI 后 73±7 天的 P/AI 以发情期 AI（58.8%）的小母牛最高，并且 CIDR5（42%）的 P/AI 似乎高于 CIDR7（34.1%）的小母牛。与 CIDR7（31.8%）相比，CIDR5 小母牛的自发黄体溶解率从 CIDR 插入到 CIDR 取出时降低（13.8%比 31.8%）。发情期 AI 小母牛的妊娠率最高，但与 CIDR5（调整后的危险比（95%置信区间）=0.75（0.63，0.90））和 CIDR7（调整后的危险比（95%置信区间）=0.65（0.54，0.77））小母牛之间无差异。因此，发情期 AI 小母牛的饲养成本和投入成本（$67.1±4.4 和 -$107.1±7.0）分别低于 CIDR5（$86.9±5.1 和 -$143.4±8.1）和 CIDR7（$98.3±5.1 和 -$156.5±8.2）的小母牛，但 CIDR5 和 CIDR7 小母牛之间没有差异。
