Journal of Animal Science, Vol 71, Issue 9 2310-2321, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Effect of source of supplemental nitrogen on the utilization of citrus pulp-based diets by sheep

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

Two trials were conducted to examine the influence of N enrichment of dried citrus pulp (DCP) through ammoniation vs urea supplementation on digestion and feeding value of a DCP-based diet for sheep. Treatments were 1) ammoniation of DCP with urea (CP-U), 2) ammoniation with ammonium hydroxide (CP-A), 3) supplementation with urea, and 4) supplementation with horse bean (HB). Diets were isonitrogenous (1.8% N). In Trial 1, treatment effects on characteristics of digestion were evaluated in a 4 x 4 Latin square experiment using four rams. Source of supplemental nonprotein N (NPN) did not influence (P > .10) ruminal OM digestion. Net microbial N synthesis, N absorption, N retention, and microbial efficiency were greater (P < .05) for the CP-U than for the CP-A or urea diets. Apparent N digestibility of CP-A was 14 to 25% lower (P < .05) than that of the other diets supplemented with NPN. In Trial 2, treatment effects on lamb growth performance were evaluated in a 105-d growing-finishing trial involving 32 Sardi lambs (19 kg). Intake was similar (P > .10) across treatments (1.13 kg of DM/d). Daily gain of the urea-fed lambs (182 g) was higher (P < .05) than that of CP-U- or CP-A-fed lambs (138 g). Feed efficiency and dietary NE values were similar (P > .10) among diets containing NPN. Growth performance seemed to be more directly affected by intake, rather than N economy. Enrichment of DCP through ammoniation with urea was a superior method of NPN supplementation with respect to efficiency of N utilization. However, the ultimate response to the potential benefits of such treatment may be seen only if N is truly limiting performance.