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Amino Acid Supplementation of Urea-Rich Diets for Lambs

Oklahoma Agricultural Experiment Station, Stillwater^,3

Abstract

Six pairs of twin lambs (average weight 18 kg.) were allotted at random within pairs into two treatment groups for a 41-day growth trial. The control group was fed a purified diet, in which urea was the nitrogen source, while the other group was fed the same diet except that it was supplemented with leucine, isoleucine, valine and phenylalanine at levels of 0.28, 0.16, 0.16 and 0.18% of the diet, respectively. The level of urea in the supplemented diet was reduced from 4.20 to 4.02% in order to make both diets isonitrogenous. All animals were fed ad libitum and blood and rumen fluid samples were collected 2 hr. after feeding on the last day of the trial. Supplemental amino acids had no significant effect on: (1) daily gain or feed intake; (2) blood hematocrit or hemoglobin levels; (3) plasma concentration of (a) total- or ammonia-nitrogen, and (b) acetic, propionic, n-butyric, isobutyric, isovaleric+2-methy butyric or valeric acid concentrations. These results indicate that ruminal synthesis of branched-chain fatty acids was not the major growth-limiting factor in lambs fed a purified diet in which urea is the sole nitrogen source.

¹ Present address: Department of Animal Science, Cornell University, Ithaca, New York.

² Department of Animal Science.

³ Approved by the Director.