Abstract：
Our objective was to compare insemination rate and pregnancies per artificial insemination (P/AI) of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for timed artificial insemination (TAI) versus a protocol to synchronize estrus at similar days in milk (DIM). Secondary objectives were to determine the effect of protocol synchrony and postpartum body condition score (BCS) change on P/AI. Lactating Jersey cows (n = 1,272) were allocated by odd versus even ear tag number, which was randomly allocated within the herd, within parity and semen type for submission to a Double-Ovsynch protocol (DO; n = 707) or a protocol to synchronize estrus (ED; n = 565). All ED cows detected in estrus were inseminated (EDAI; n = 424), with undetected cows receiving TAI after an Ovsynch protocol (EDTAI; n = 141). There was a treatment by parity interaction on insemination rate with 100% of DO cows receiving TAI, but a tendency for fewer primiparous ED cows to be detected in estrus and AI than multiparous cows (69.5% ± 0.04% vs. 77.1% ± 0.02%, respectively). For cows inseminated with sexed Jersey or conventional beef semen, DO cows tended to have and had more P/AI than EDAI cows (sexed, 49.2% ± 0.03% vs. 43.6% ± 0.03%; beef, 64.2% ± 0.04% vs. 56.3% ± 0.05%, respectively) and had more P/AI than EDAI+EDTAI cows (sexed, 49.1% ± 0.03% vs. 40.6% ± 0.03%; beef, 65.5% ± 0.04% vs. 56.2% ± 0.04%, respectively). Overall, 29.1% of DO cows expressed estrus with 5.0% and 24.2% of cows detected in estrus ≥24 h before and at TAI, respectively, and there was no difference in P/AI 61 ± 4 d after AI based on expression of estrus at TAI. The synchronization rate was greater for DO than EDAI cows (92.1% ± 0.01% vs. 79.2% ± 0.02%, respectively); however, synchronized DO cows had more P/AI than synchronized EDAI cows (55.0% ± 0.02% vs. 49.2% ± 0.03%, respectively). There was an interaction between BCS change from 7 to 39 ± 2 DIM and treatment on P/AI 61 ± 4 d after AI with no difference between DO and EDAI cows that lost = 0.25 (49.8% ± 0.04% vs. 51.0% ± 0.05%, respectively) or maintained or gained (55.6% ± 0.04% vs. 50.8% ± 0.05%, respectively) BCS, but within cows that lost ≥0.5 BCS, DO cows had more P/AI than EDAI cows (54.1% ± 0.04% vs. 36.1% ± 0.04%, respectively). In conclusion, submission of lactating Jersey cows to a Double-Ovsynch protocol for first insemination increased insemination rate and fertility to first insemination compared with AI after a detected estrus regardless of semen type and expression of estrus, particularly for cows with excessive postpartum BCS loss.
摘要：
我们的目标是比较在提交给定时人工授精（TAI）的Double-Ovsynch协议后，首次使用性别泽西或常规牛肉精液进行授精的泌乳泽西母牛的授精率和每次人工授精（P/AI）的妊娠率。次要目标是确定方案同步性和产后身体状况评分（BCS）变化对P/AI的影响。哺乳期泽西奶牛（n=1,272）由奇数与甚至耳标号码，在群体中随机分配，在奇偶校验和精液类型内，用于提交Double-Ovsynch协议（DO;n=707）或同步发情协议（ED;n=565）。在发情期中检测到的所有ED母牛都被授精(EDAI;n=424),未检测到的母牛在Ovsynch方案(EDTAI;n=141)后接受TAI。通过胎次相互作用对授精率进行处理，100％的DO奶牛接受TAI，但是在发情和AI中检测到的初产ED母牛比多产母牛少的趋势（69.5±0.04与77.1±0.02%,分别)。对于用性别泽西或传统牛肉精液授精的奶牛，DO奶牛倾向于拥有和拥有比EDAI奶牛更多的P/AI(性别，49.2±0.03vs.43.6±0.03%；牛肉，64.2±0.04vs.56.3±0.05%,分别)，并且比EDAI+EDTAI奶牛有更多的P/AI(性别，49.1±0.03vs.40.6±0.03%；牛肉，65.5±0.04vs.56.2±0.04%，分别)。总的来说,29.1％的DO母牛表现出发情，5.0％和24.2％的母牛在TAI之前和在发情期≥24小时时检测到，分别,根据TAI发情的表达，AI后P/AI61±4d无差异。DO的同步率高于EDAI奶牛（92.1±0.01vs.79.2±0.02%,分别)；然而，同步DO母牛比同步EDAI母牛具有更多的P/AI（55.0±0.02与49.2±0.03%,分别)。从7到39±2DIM的BCS变化与AI后P/AI61±4d的处理之间存在相互作用，DO和EDAI母牛之间没有差异，损失=0.25（49.8±0.04与51.0±0.05%，分别）或维持/增加（55.6±0.04与50.8±0.05%,分别)BCS，但是在损失≥0.5BCS的奶牛中，DO奶牛的P/AI比EDAI奶牛多（54.1±0.04与36.1±0.04%,分别)。总之,与检测到发情后的AI相比，无论精液类型和发情表达如何，将泌乳泽西母牛提交给首次授精的Double-Ovsynch方案增加了首次授精的授精率和生育力，特别是对于产后BCS损失过多的奶牛。
