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Urea-Treated Corn Silage as the Only Forage for Lactating Cows

Department of Dairy Science, Virginia Polytechnic Institute, Blacksburg

ABSTRACT

Two experiments were conducted to determine the feeding value of corn silage to which from 0.5 to 0.85% urea was added at the time of ensiling. The per cent of total ration nitrogen furnished by added urea averaged 0, 14.8 and 26.8 in Experiment 1 and 0, 25.2 and 38.0 in Experiment 2. Treatment periods for the respective experiments were 70 and 63 days. Concentrates were formulated so that rations within each experiment were isonitrogenous and isocaloric. Milk production was not significantly affected by consumption of urea-treated corn silage. However, in both experiments per cent milk protein was lowest (P < .05) at the highest level of urea. Neither silage dry matter nor total dry matter intakes were affected by urea treatment. Difference between treatments in several volatile fatty acids were observed in Experiment 1 but not in Experiment 2. Blood serum urea and rumen ammonia were generally increased as urea in the ration increased. In Experiment 2 crude protein digestibility was least (P < .01) and urinary nitrogen excretion greatest (P < .01) at the highest level of urea; thus resulting in considerable negative nitrogen balance for cows on this treatment (P < .01).

¹ Present address: Department of Dairy, Michigan State University, East Lansing.