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Protein Requirements of Milking Cows¹

Department of Dairy Science, Michigan State University, East Lansing 48823

ABSTRACT

During a short trial of 90 days and a longer trial of two lactations, cows were fed a ration containing about 10.7 or 12.6% protein. Cows received concentrate at 1 kg per 2.5 kg milk, and total digestible nutrient intake averaged 113 to 120% of requirement. Sufficient energy was fed so that differences in protein intake might be reflected in production. Cows on the short trial produced similar amounts of milk (18 to 20 kg/day), fat-corrected milk and fat with equal persistency on both rations (8 Holsteins/ration). In the longer trial 28 cows started on assigned diet at 45 days postpartum. Those receiving the lower protein diet produced less milk (P < .05) but not fat than predicted for the remainder of that lactation. Cows with previous production records also produced less during the first or second experimental lactation on the low protein ration than they had previously. No change was noted for those on the higher protein diet. Persistency was somewhat less (89 versus 9576, P < .1 to .05) for those on lower protein. Actual 305-day production averaged 6,582 (3,900 to 9,493) kg milk for 8 cows on the low protein diet compared to 7,893 (6,257 to 9,265) for 6 cows fed the higher protein for their second lactation on these rations. These values represent 102 and 95% of yield during first lactation on these rations.

¹ Published with the approval of the Director of the Agricultural Experiment Station as Journal Article 5432.