Abstract

The future efficiency of the dairy industry will undoubtedly be affected by the decline in fertility and reproductive efficiency in modern dairy cows. The cause of the declining fertility is probably a combination of genetic, physiological and management factors that have an additive effect on reproductive efficiency. Milk production per cow has increased and is one factor that is contributing to the problem. In addition to milk production, however, many other equally important factors may be involved. For example, the reproductive physiology of dairy cattle has changed in response to genetic selection for milk production and these changes may require different management strategies. Compared to traditional dairy cows, modern dairy cows have longer intervals to first ovulation, a higher incidence of anoestrus, abnormal luteal phases, lower blood progesterone concentrations, and greater embryonic loss. Reproductive decline can be reversed in dairy cows but a collective effort that includes more intense reproductive management, genetic selection for improved fertility, and new scientific discoveries will be necessary before the problem can be solved.

MC, Lucy

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 120-127, 2001