Interactions of nutrition and reproduction.

As dairy cattle achieve higher milk production, we are becoming aware of closer relationships between nutrition and fertility. An increasing body of evidence indicates that excessive protein intake in early lactation may be detrimental to postpartum fertility. In addition, protein solubility and degradability are important. Energy restriction in high producing cows may be detrimental to fertility through its effect on hypothalamic and ovarian function. Dairy producers are susceptible to advertisements advocating the addition of specific vitamins and minerals to the rations of high producing cows since inadequate or excessive quantities may be detrimental to fertility. This is particularly true for minerals. However, high producing cows do not usually receive grossly inadequate or excessive dietary sources of vitamins and minerals. Rather, they may be presented with a borderline intake of several vitamins and minerals, which together may be detrimental to fertility. Finally, new methods must be developed to provide a more sensitive indication of fertility. These are some of the research and educational needs of the dairy industry if it is to continue successfully increased milk production. Predictions of herd averages of 16,000 kg milk and individual records exceeding 30,000 kg have been made for the yr 2000.