Cabrera V E
Animal and Dairy Sciences Department, University of Wisconsin-Madison, Madison 53706.
JDS Commun. 2021 Nov 25;3(2):147-151. doi: 10.3168/jdsc.2021-0155. eCollection 2022 Mar.
The economic value of using beef semen in dairy herds depends on the market value of calves (crossbred beef and dairy), market price of semen (beef, conventional, and sexed), herd reproductive performance, and semen combination strategies. Due to the complex interaction among all these factors and their inherent changing conditions, the quest for an optimal strategy is best served by the application of an integrated model and a decision support tool adaptable to ever-changing farm and market conditions. We have developed a model and a decision support tool to calculate the income from calves over semen costs (ICOSC) in response to user-defined beef semen crossbreeding strategies in combination with sexed and conventional semen utilization. The model follows a Markov-chain approach in which animal (heifer and cow) statuses (age, months after calving, lactation, pregnancy, calving) are simulated monthly. Replacement balance is calculated as the difference between demand and supply of calves in function of selected semen utilization protocols, which could include beef, sexed, or conventional semen. A case study was performed in a 1,000-cow virtual Holstein herd with 35% turnover rate and 7% stillbirth rate. Five strategies of beef semen utilization on adult cows (0 to 100% in 25-percentage-unit intervals) were combined with 6 strategies of sexed semen use [none (NS), first service in heifers (1H), first and second services in heifers (2H), 2H + 20% top genetic cows (TOP), 2H + first service in primiparous (1C), and 1C + first service in second-lactation cows (2C)]. All animals not bred to either sexed or beef semen were bred to conventional semen. Having a price of beef calves 4 times greater than the price of a dairy calf and having the price of sexed semen ~2.3 times greater than the conventional or beef semen determined that the optimal breeding semen protocols that concurrently maximized the ICOSC and produced enough replacements were 100% beef semen use after 2C sexed semen protocol (ICOSC = $2,001) for medium reproductive performance (20% 21-d pregnancy rate) and 100% beef semen after 1H sexed semen protocol (ICOSC = $6,215) for high reproductive performance (30% 21-d pregnancy rate). These strategies were consistently the best options under several feasible market conditions for herds with medium and high reproductive performance. However, the optimal ICOSC was negative or marginally low for low-performance herds (15% 21-d pregnancy rate), for which the opportunity to use beef semen is minimal or nonexistent.
在奶牛群中使用牛肉精液的经济价值取决于犊牛（杂交肉牛和奶牛）的市场价值、精液的市场价格（牛肉精液、常规精液和性别分选精液）、牛群的繁殖性能以及精液组合策略。由于所有这些因素之间复杂的相互作用及其固有的变化情况，通过应用一个综合模型和一个能够适应不断变化的农场和市场条件的决策支持工具，最有助于寻求最佳策略。我们开发了一个模型和一个决策支持工具，用于根据用户定义的牛肉精液杂交策略以及性别分选精液和常规精液的使用情况，计算犊牛收入减去精液成本（ICOSC）。该模型采用马尔可夫链方法，每月模拟动物（小母牛和母牛）的状态（年龄、产犊后月龄、泌乳、怀孕、产犊）。根据选定的精液使用方案（可能包括牛肉精液、性别分选精液或常规精液），计算犊牛供需差异来确定后备牛平衡。在一个拥有1000头奶牛的虚拟荷斯坦牛群中进行了案例研究，该牛群的周转率为35%，死胎率为7%。将成年母牛使用牛肉精液的五种策略（以25个百分点的间隔从0到100%）与六种性别分选精液使用策略[不使用（NS）、小母牛首次输精（1H）、小母牛首次和第二次输精（2H）、2H + 20%顶级遗传母牛（TOP）、2H + 初产母牛首次输精（IC）、IC + 二胎泌乳母牛首次输精（2C）]相结合。所有未使用性别分选精液或牛肉精液输精的动物都使用常规精液输精。由于肉牛犊价格约为奶牛犊价格的4倍，性别分选精液价格约为常规精液或牛肉精液价格的2.3倍，因此对于中等繁殖性能（约20%的21天怀孕率），在2C性别分选精液方案后使用100%牛肉精液（ICOSC = 2001美元）以及对于高繁殖性能（约30%的21天怀孕率），在1H性别分选精液方案后使用100%牛肉精液（ICOSC = 6215美元）是同时使ICOSC最大化并产生足够后备牛的最佳输精精液方案。对于中等和高繁殖性能的牛群，在几种可行的市场条件下，这些策略始终是最佳选择。然而，对于低性能牛群（约15%的21天怀孕率），最佳ICOSC为负或略低，在这种情况下使用牛肉精液的机会微乎其微或不存在。
