Production and reproduction in dairy cows

Abstract

Economic models suggest maximum income is realized when cows calve every 12 to 13 months. Increasingly, farmers have questioned the feasibility and economic justification of achieving a 12 to 13 month calving interval in cows producing over 9,000 kg of milk. Concerns have arisen over two issues. One is biological: are higher yields of milk associated with reduced conception rate (CR); the other is managerial: are longer calving intervals more profitable in higher producers. Breeding is often delayed in high producing cows, particularly when expensive semen is used, because managers feel CR is reduced at days in milk that correspond to a yearly calving interval. Additionally, the impression exists that higher producing cows make more money when calving intervals are longer than average producing herd mates. This paper will examine the biological and managerial relationships between milk yield and reproduction.