Effects of Dietary Protein Concentration on Lactating Cows

Abstract

Eighteen Holstein cows were used for three consecutive lactations to compare 13, 15, and 17% protein rations. Cows were assigned to six 3 x 3 Latin squares. Each cow was fed individually and received a different protein concentration for an entire lactation. Alfalfa hay and the designated concentrate were fed ad libitum twice daily. Cows receiving the 15 or 17% protein rations produced more milk, fat, protein, and milk solids-not-fat than those receiving the 13% protein ration. Percentages of milk components did not differ among rations. Cows receiving the 13% protein ration consumed less concentrate than those receiving the 15% or 17% rations. Hay, total dry matter intake, body weight, services per conception, or days cows were open were not different among dietary protein concentrations.