Fertility in the high-producing dairy cow

Genetic correlations between milk yield and reproductive measures in dairy cows are unfavourable. This suggests that successful selection for higher yields may have led to a decline in fertility. There is also evidence that an imbalance of nutrients, in either high genetic merit cows or those fed diets. not matched to their performance, leads to poorer reproductive performance. Physiological reasons for the antagonism have not been elucidated. In this paper we examine the complexity of genetic, nutritional, physiological and management factors of the yield versus fertility antagonism. To maintain or recover high fertility in modem dairy cows calls for a two-pronged approach involving both inclusion of fertility in broader breeding goals and adjustment to management practices. (C) 2003 Elsevier B.V. All rights reserved.