Department of Animal Science, Sari Agricultural Sciences and Natural Resources University, Sari, Mazandaran, Iran.
Leduc Farm Animal Hospital, Leduc, Canada.
Reprod Domest Anim. 2024 Aug;59(8):e14696. doi: 10.1111/rda.14696.
This study compared reproductive outcomes among two protocols for synchronization of ovulation that provide for a lengthened proestrus with the conventional oestradiol-based protocol currently used for timed-AI (TAI). Holstein heifers (13-15 months) at one location were assigned randomly to one of three TAI protocols. Heifers (n = 150) in the 7-day oestradiol benzoate (EB) group received a progesterone device (Cue-Mate) and 2 mg EB on Day 0; 500 μg of cloprostenol (PGF) and Cue-Mate removal on Day 7; 1 mg of EB on Day 8 and TAI on Day 9 (54 h after Cue-Mate removal). Heifers (n = 150) in the 5-day CO-Synch (CO) group received a Cue-Mate and 100 μg of gonadotropin-releasing hormone (GnRH) on Day 2; Cue-Mate removal and PGF (twice, 12 h apart) on Day 7; and GnRH along with TAI on Day 10 (72 h after Cue-Mate removal). Heifers (n = 150) in the J-Synch (JS) group received a Cue-Mate and 2 mg of EB on Day 1; PGF and Cue-Mate removal on Day 7; GnRH and TAI on Day 10 (72 h after Cue-Mate removal). Heifers were inseminated by one technician with frozen-thawed conventional semen from one of four commercially available sires. Plasma progesterone (P4) concentrations (ng/mL) were determined at Cue-Mate removal and TAI. Ovarian ultrasonography was done in a subset of 217 heifers at the initiation of protocols, at Cue-Mate removal; TAI; and 7 days after TAI. Approximately, 28 and 50 days after TAI pregnancy status was determined by ultrasonography. Mean (±SEM) plasma P4 concentration at Cue-Mate removal was greater (p < .01) in CO (6.02 ± 0.2) and JS (6.51 ± 0.2) compared to EB heifers (4.53 ± 0.2). Mean (±SEM) plasma P4 concentration at TAI was lowest in the JS (0.28 ± 0.05), intermediate in CO (0.46 ± 0.02), and greatest in EB heifers (0.66 ± 0.05, p < .01). The diameter of the ovulatory follicle (mean ± SEM) was the smallest in the JS group compared to that in the CO and EB groups (15.8 ± 0.5; 13.9 ± 0.5; and 12.7 ± 0.5 mm for EB, CO and JS, respectively). More (p < .01) heifers in the JS group had their oestrous cycle synchronized (50.0, 78.8 and 82.4% for EB, CO and JS groups), and were pregnant at 28 (40.3, 51.3 and 63.3% for EB, CO and JS groups) and 50 days after TAI (32.6, 46.0 and 60.0% for EB, CO and JS groups). In summary, heifers subjected to the J-Synch TAI protocol had lower P4 at TAI, and better overall response to hormonal treatments, which resulted in increased P/AI at 28 and 50 days after TAI compared to those heifers subjected to either a 7-day EB protocol or a 5-day CO-synch protocol.
本研究比较了两种排卵同步方案的生殖结果，这两种方案为传统的雌激素基础定时人工授精（TAI）方案提供了延长的发情前期。在一个地点的荷斯坦小母牛（13-15 个月）被随机分配到三个 TAI 方案之一。EB 组（n=150）的小母牛在第 0 天接受孕激素装置（Cue-Mate）和 2mg EB；第 7 天接受 500μg 氯前列醇（PGF）和 Cue-Mate 去除；第 8 天接受 1mg EB，第 9 天（Cue-Mate 去除后 54 小时）进行 TAI。CO-Synch（CO）组（n=150）的小母牛在第 2 天接受 Cue-Mate 和 100μg 促性腺激素释放激素（GnRH）；第 7 天接受 Cue-Mate 去除和 PGF（两次，间隔 12 小时）；第 10 天接受 GnRH 和 TAI（Cue-Mate 去除后 72 小时）。JS 组（n=150）的小母牛在第 1 天接受 Cue-Mate 和 2mg EB；第 7 天接受 PGF 和 Cue-Mate 去除；第 10 天接受 GnRH 和 TAI（Cue-Mate 去除后 72 小时）。小母牛由一名技术员用来自四个商业来源的常规精液进行冷冻解冻授精。在 Cue-Mate 去除和 TAI 时测定血浆孕酮（P4）浓度（ng/mL）。在方案开始时、Cue-Mate 去除时、TAI 时和 TAI 后 7 天对 217 头小母牛进行了卵巢超声检查。TAI 后约 28 和 50 天通过超声检查确定妊娠状态。在 CO（6.02±0.2）和 JS（6.51±0.2）组，Cue-Mate 去除时的平均（±SEM）血浆 P4 浓度（p<.01）高于 EB 组（4.53±0.2）。在 JS 组（0.28±0.05），TAI 时的平均（±SEM）血浆 P4 浓度最低，CO 组（0.46±0.02）居中，EB 组（0.66±0.05，p<.01）最高。排卵卵泡的直径（平均值±SEM）在 JS 组最小，与 CO 和 EB 组相比（15.8±0.5；13.9±0.5；12.7±0.5mm 分别为 EB、CO 和 JS 组）。JS 组（p<.01）同步发情的小母牛数量更多（EB、CO 和 JS 组的发情周期同步率分别为 50.0%、78.8%和 82.4%），TAI 后 28 天（EB、CO 和 JS 组的妊娠率分别为 40.3%、51.3%和 63.3%）和 50 天（EB、CO 和 JS 组的妊娠率分别为 32.6%、46.0%和 60.0%）怀孕的小母牛更多。总之，与 EB 方案或 7 天 CO 方案相比，接受 J-Synch TAI 方案的小母牛在 TAI 时的 P4 水平较低，对激素治疗的整体反应更好，这导致 TAI 后 28 和 50 天的 P/AI 增加。
