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Protein Requirements of Cows Fed High Concentrate Rations

Department of Animal Science, Brigham Young University, Provo, Utah 84601

ABSTRACT

In Experiment I, 96 multiparous Holstein cows were assigned at calving to rations containing 13.2, 14.4, and 15.5% crude protein in dry matter. Daily dry matter intake per cow was 4.2 kilograms corn silage, 5.9 kilograms alfalfa hay, and 10.8 kilograms concentrates. In Experiment II, 88 cows at calving were assigned to rations with 13.9 and 15.8% crude protein in dry matter. Daily dry matter intake was 3.8 kilograms corn silage, 8.4 kilograms alfalfa hay, and 10.0 kilograms concentrates. Amount of concentrate offered was reduced to 4 kilograms per cow daily in each experiment if milk production declined to less than 18 kilograms daily or the cow gained more than 45 kilograms body weight over calving weight. In both experiments cows were offered either 115 or 170% of maintenance energy needs during the 60-day dry period resulting in 2 x 3 (Experiment I) and 2 x 2 (Experiment II) factorial arrangements of treatments.

Average unadjusted 305-day yields in response to ration protein values of 13.2, 14.4, and 15.5% were 6,582, 6,941, and 7,321 kilograms milk; 211, 228, and 223 kilograms fat; 564, 595, and 632 kilograms solids-not-fat; and milk protein percentages of 3.33, 3.27, and 3.37. Comparative production results from dietary proteins of 13.9 and 15.8% in Experiment II were 6,647 and 7,256 kilograms milk, 231 and 250 kilograms fat, and 564 and 614 kilograms solids-not-fat. Prepartum energy treatments did not affect lactation.