Urea Versus Biuret in a Roughage Diet for Steers

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Abstract
A metabolism trial was conducted with steers to study the value of urea and biuret in an 85% roughage diet. These non-protein nitrogen sources supplied about 50% of the total nitrogen in the diet. The steers were changed abruptly from a soybean meal supplemented roughage diet to the experimental diets and metabolism collections were made at 7, 21, 42, 77 and 119 days. Nitrogen (% of intake) in the feces, urine and retention for the urea and biuret diets, respectively, were: 25.5, 29.3; 46.9, 47.9; 27.6, 22.8. Fecal nitrogen and nitrogen retention were both influenced (P<.01) by period and diet x period. Nitrogen balance indicated that steers fed urea were adapted to the diet after 7 days, whereas steers fed biuret were not adapted to the diet until it was fed for 21 days. Diethylstilbestrol had no effect on nitrogen balance or adaptation to either diet. Many of the blood plasma free amino acid concentrations were affected by the criteria studied. In general, there was a decrease in the concentration of most of the amino acids after feeding compared to before feeding. A growth trial was conducted to study the performance of steers fed the diets on an ad libitum and then twice daily feeding basis during 84 day periods. Daily gains (kg.) during these periods for the urea and biuret diets, respectively, were: 0.81, 0.74; 0.15, 0.46. Gains were influenced by period (P<.01) and diet x period (P<.05). Ruminal ammonia concentrations, VFA and microbial population patterns were similar for both nitrogen sources in both trials. Copyright © 1969. American Society of Animal Science . Copyright 1969 by American Society of Animal Science

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