Fricke P M, Carvalho P D, Giordano J O, Valenza A, Lopes G, Amundson M C
Department of Dairy Science,University of Wisconsin,Madison,WI 53706-1205,USA.
Animal. 2014 May;8 Suppl 1:134-43. doi: 10.1017/S1751731114000299. Epub 2014 Mar 28.
Despite the widespread adoption of hormonal synchronization protocols that allow for timed artificial insemination (AI), detection of estrus plays an important role in the reproductive management program on most dairies in the United States. Increased physical activity is a secondary sign of estrus in dairy cattle, and a new generation of electronic systems that continuously monitor physical activity to predict timing of AI have been developed and marketed to the dairy industry. A variety of management and physiologic challenges inhibit detection of behavioral estrus on farms, but the prevalence of anouvular cows near the end of the voluntary waiting period is particularly problematic. Only 70% of lactating Holstein cows were detected in estrus when using an activity monitoring system, with the remaining 20% of cows classified as anovular and 10% ovulating without showing signs of activity. Mean time of AI in relation to ovulation based on the activity monitoring system was acceptable for most of the cows with increased activity, however, variability in the duration of estrus and timing of AI in relation to ovulation could result in poor pregnancy outcomes in some cows. Use of a Presynch-Ovsynch protocol for submission of cows for first AI has been widely adopted by dairies in the United States, and a combined approach in which AI based on activity is followed by submission of cows not detected with activity to timed AI after synchronization of ovulation may be an effective strategy for submission of cows to first AI. Based on a field trial on a large commercial dairy in the United States, the activity monitoring system detected 70% of cows with increased activity after the second PGF2α injection of a Presynch-Ovsynch protocol, however, cows inseminated to increased activity had fewer pregnancies per AI (P/AI) compared with cows with increased activity after the second PGF2α injection that received timed AI after completing the Presynch-Ovsynch protocol. Based on an economic model comparing reproductive management programs with varying levels of AI to estrus v. timed AI, the rate of estrus detection and the P/AI to inseminations based on AI to detected estrus v. timed AI affected the decision to inseminate based on activity v. timed AI. In conclusion, an activity monitoring system detected increased activity in about 70% of lactating Holstein cows on a large commercial dairy in the United States, however, synchronization of ovulation and timed AI was beneficial to inseminate cows not detected with increased activity by the activity monitoring system.
尽管广泛采用了能实现定时人工授精（AI）的激素同步方案，但在美国大多数奶牛场，发情检测在繁殖管理计划中仍起着重要作用。活动量增加是奶牛发情的次要迹象，新一代持续监测活动量以预测人工授精时间的电子系统已被开发并推向奶牛行业。农场中存在各种管理和生理挑战，阻碍了对行为发情的检测，而在自愿等待期快结束时，不排卵奶牛的比例尤其成问题。使用活动监测系统时，只有70%的泌乳荷斯坦奶牛能被检测出发情，其余20%的奶牛被归类为不排卵，10%的奶牛排卵但未表现出活动迹象。对于大多数活动量增加的奶牛来说，基于活动监测系统的人工授精相对于排卵的平均时间是可以接受的，然而，发情持续时间和人工授精相对于排卵时间的变异性可能导致一些奶牛的妊娠结果不佳。在美国，奶牛场广泛采用Presynch - Ovsynch方案进行首次人工授精，对于活动监测系统未检测到活动的奶牛，在排卵同步后进行定时人工授精的联合方法，可能是奶牛首次人工授精的有效策略。基于美国一家大型商业奶牛场的田间试验，活动监测系统在Presynch - Ovsynch方案的第二次PGF2α注射后，检测到70%活动量增加的奶牛，然而，与在完成Presynch - Ovsynch方案后接受定时人工授精且第二次PGF2α注射后活动量增加的奶牛相比，因活动量增加而进行人工授精的奶牛每次人工授精的妊娠数（P/AI）较少。基于一个经济模型，该模型比较了不同人工授精水平（发情人工授精与定时人工授精）的繁殖管理方案，发情检测率以及基于发情人工授精与定时人工授精的人工授精妊娠率（P/AI）影响了基于活动量人工授精与定时人工授精的授精决策。总之，在美国一家大型商业奶牛场，活动监测系统检测到约70%的泌乳荷斯坦奶牛活动量增加，然而，排卵同步和定时人工授精对于活动监测系统未检测到活动量增加的奶牛进行授精是有益的。
