Influence of Varying Amounts of Urea on the Fermentation Pattern and Nutritive Value of Corn Silage

Abstract

Urea, in amounts of either 0%, .5% or .75%, was added to silages containing 37 to 40% dry matter (DM) in Experiment I (1968) and 38 to 42% DM in Experiment II (1969). Acetic acid production in all silages was essentially complete after 5 days of fermentation while lactic acid production continued for 25 days. The production of propionic, butyric, and lactic acids increased (P < .01) with increasing amounts of urea. Acetic acid production increased (P < .01) with the addition of .75% urea but was slightly depressed by the addition of .50% urea (P < .05). Approximately 65 to 73% of the urea-nitrogen was converted to other forms. Increased NH3-N accounted for 23 to 44% of this decrease in urea-N. In the lactation trials, 24 Holstein cows were in a 3 × 3 Latin square design with three 28-day periods. Experimental silages were fed in amounts to maintain 10% weigh back daily. Diets were isonitrogenous and isocaloric. In Experiment I, cows fed 0% and .50% urea silages consumed more (P < .01) silage dry matter than cows fed .75% urea silage while in Experiment II cows fed .50% urea silage consumed the most silage DM (P < .01). Milk production (4% fatcorrected milk) was not significantly affected by treatments in Experiment I, but in Experiment II cows fed .50% urea silage produced more fat-corrected milk than did the other treatment groups (P < .05). Cows fed control silage in Experiment I gained more weight than those fed .75% urea silage (P