Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: July 29, 1997
Publication Date: N/A
Technical Abstract: The majority of N fed to beef cattle is excreted in the urine and feces. Improved utilization of dietary N would result in smaller amounts of N being lost to the environment. The present studies were conducted to determine the effect of intermittent protein supplementation on nutrient balance of lambs fed a high-concentrate diet. Ten St Croix lambs (avg. BW-20 kg) were used in two 5 x 5 Latin square experiments. In each experiment dietary treatments consisted of the following: 1) 10% CP, 2) 12.5% CP, 3) 15% CP, 4) 10% and 15% CP diets alternated daily (A1), and 5) 10% and 15% CP diets alternated every other day (A2). In Exp. 1, supplemental N was provided by cottonseed meal, and in Exp. 2, was provided by a 50:50 (N basis) blend of cottonseed meal and urea. All diets contained 10% roughage (50:50 cottonseed hulls: alfalfa. Each period of the Latin square was 28 d with an 8 d urine and fecal collection. Dietary treatment did not affect DM digestibility in either trail (Mean: 85.1 +/- .25%). Nitrogen retention increased linearly (P < .01) with increased N intakes in both trials (.77, 1.36, and 1.89 g/d for 10%, 12.5%, and 15%, respectively in Exp. 1; .84, 1.43, and 2.19 g/d for 10%, 12.5%, and 15% respectively in Exp. 2). Compared to lambs continuously fed the 12.5% CP diet, alternating CP intake on a daily basis (A1) did not significantly affect N retention in either experiment (1.62 and 1.57 g/d for Exp. 1 and 2, respectively). However, alternating CP intake every other day (A2) increased (P < .05) N retention 38% in Exp. 1 (1.87 g/d), primarily the result of a nonsignificant decrease in urinary N excretion. These results suggest that alternating dietary CP concentration could potentially improve N utilization in ruminants fed high-concentrate diets.