Journal of Animal Science, Vol 71, Issue 6 1657-1665, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Influence of level of urea and method of supplementation on characteristics of digestion of high-fiber diets by sheep

N. Rihani, W. N. Garrett and R. A. Zinn
Institut Agronomique et Veterinaire Hassan II, Rabat Instituts, Morocco.

Effects of level and method of urea supplementation of N utilization and characteristics of digestion of a N-deficient (.85% N), citrus pulp-based diet were evaluated in a 4 x 4 Latin square design experiment, using four ruminally and intestinally cannulated crossbred (D'man x Sardi) rams. Two levels of urea (15.1 and 8.8 g/d, providing total N intakes of 12.0 and 9.1 g/d, respectively) and two methods of supplementation (urea mixed with the diet or continuously infused in the rumen) were compared in a 2 x 2 factorial arrangement of treatments. Ruminal pH varied between 6.2 and 7.0 across treatments and tended (P > .10) to be lower in animals receiving urea infusion. Ruminal ammonia concentrations were lower (P < .01) and more stable with urea infusion than with urea feeding. Ruminal VFA concentrations and profiles were unaffected (P > .10) by treatments. Site and extent of OM and fiber digestion were not influenced (P > .10) by either level of urea in the diet or method of supplementation. Average ruminal OM and ADF digestion were 53.1 and 64.5%, respectively. Total tract digestion values averaged 75.9 and 73.5%, respectively. With the exception of N efficiency (duodenal nonammonia N/total N intake) that was 31% lower (P < .10) for the high- than for the low-urea treatment, there were no treatment responses or interactions (P > .10) on characteristics of N utilization. Microbial N flow to the small intestine averaged (across treatments) 9.0 g/d and constituted 87% of the nonammonia N leaving the abomasum.(ABSTRACT TRUNCATED AT 250 WORDS)