Nutrition and fertility in dairy cows.

Introduction It is now widely recognised that reduced fertility in dairy herds is one of the most important factors affecting producer profitability. Roche (2006) has defined the effect of infertility on profitability as: (i) prolonged calving interval with fewer calves and less milk per cow; (ii) increased replacement costs; (iii) increased labour, semen and veterinary bills; and (iv) an extended low production or dry period which increases BCS (body condition score) at calving and also reduces fertility at the subsequent breeding season. While published targets for fertility parameters are often achieved in research centres and on some commercial dairy farms, there is a tremendous amount of variation in fertility performance between farms and, in general, the fertility performance achieved on commercial Irish farms is often much lower than the quoted targets (Mayne et al., 2002; Mee and Buckley, 2003). Dairy farmers have consequently become more aware that poor dairy herd fertility is costing them large amounts of money. Therefore, the impetus to improve fertility on Irish dairy farms has never been greater. However, it must always be remembered that infertility is a multi-factorial problem and that approaches to solve such problems at herd level must consider a vast range of possible causative factors. This article will deal with nutritional factors that are of importance for dairy cow fertility. It is primarily based on review papers presented at two recent dairy conferences held at University College Dublin: ‘Focus on fertility’ and ‘Production diseases of the transition cow’.