Individual inseminations from the southeastern U.S. for the past 15 year period (birth years 1985-1999) were analysed. Conception rate decreases in hotter months, early in lactation, at higher yields and in recent years. Genetic gain for several different breeding objectives were predicted using parameters from Tsuruta et al., 2005 and economic values from French and Nebel, 2003 and VanRaden 2004. The economic cost of poor fertility is higher when milk yields increases, pregnancy rate decreases or breeding conditions limit the length of lactation. The value of fertility is estimated to be 4.5 times higher under a seasonal versus continual breeding situation. Improving fertility in dairy cows requires that variables, such as, genetic parameters; local economic conditions; breeding policies and long-term sustainability must be considered in designing a successful breeding programme.

Thomas J Lawlor, Ignacy Misztal, Shogo Tsuruta, C. Huang

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.35, 2006
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