Dietary Factors Affecting Utilization of Urea Nitrogen by Sheep in Purified Diets

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Abstract
A series of experiments was conducted over a period of 3 years investigating the effect of several factors on the utilization of urea in purified diets for the growth of lambs. The factors were supplements of sodium and potassium bicarbonates (cations), alfalfa and ad libitum vs. limited feeding regimens. The overall effect of cations was to improve the growth of lambs whether the dietary intake was limited or the animals were fed ad libitum. In general, the inclusion of 5% alfalfa also improved growth. An ancillary measurement which correlated with the gains was the level of lactate in the rumen; that is, in general, high levels of ruminal lactate were correlated with lower gains and vice versa. Under limited feeding conditions, both cations and alfalfa were required to decrease ruminal lactate to low levels. Evidence was obtained that the “ammonia-producing mechanism” for the excretion of anions by the kidney was stimulated when supplemental cations were omitted from the diet.