Protein, Fats and Fertility in Dairy Cows

Abstract

Levels of dietary protein that optimize milk production may depress fertility in dairy cows. While fertility responses of dairy cows fed diets with increased levels of crude protein have not been consistent, trends towards increased services/conception and days open have been reported. New concepts in ruminant protein nutriture partition crude protein into rumen undegradable and degradable fractions. Few studies investigating protein effects on fertility have accounted for partitioning of dietary protein. Dairy cows in their fourth or greater lactation are more likely to become pregnant by 120 days postpartum when fed diets balanced for rumen degradable and undegradable protein. Superovulation studies suggest fertilization failure occurs in older cows fed diets with high levels of rumen degradable protein.

Increases in milk yield has been reported in dairy cows receiving fat supplemented diets. Fats protected from rumen degradation have been advocated over vegetable oils and fat mixtures of grease and tallow. Dairy cows fed protected fats have a 2.052 risk odds ratio for pregnancy compared to cows not receiving fats. Conception rate in cows fed protected fats is 59.3% versus 41.5% in control cows. Fat included in dairy cattle rations may not only benefit production, but also reproduction.