Studies of the Adaptation Phenomenon by Lambs Fed Urea as the Sole Nitrogen Source, Chemical Alterations in Ruminal and Blood Parameters

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Abstract
TWO trials were conducted with wether lambs fed isonitrogenous purified diets containing urea or soy protein as the only nitrogen source. Ruminal and jugular blood samples were taken at 10-day intervals to determine the chemical alterations due to the substitution of urea for isolated soybean protein. At the conclusion of trial 2, ruminal contents and livers from four lambs fed each ration were assayed for certain enzyme activities. In the first trial average propionic acid concentrations were higher and butyric acid levels were lower for the lambs fed urea than for those fed soy protein. In the second trial, there were no such trends. The levels of the branched-chain VFA's were lower in both trials for the lambs fed urea. The percent ruminal NPN and ammonia nitrogen and blood urea levels were significantly higher for the urea-fed lambs. However, there was a general tendency for these parameters to decrease with time for these lambs. Blood plasma levels of tyrosine, lysine, valine and leucine were significantly lower for the urea-fed lambs compared to those fed soy protein in both trials. Isoleucine and methionine were lower for trial 1 and arginine and phenylalanine for trial 2. Serum total proteins and albumin levels decreased with time for the lambs fed both nitrogen sources. However, the decrease was greater for the lambs fed urea. The liver enzyme activity of glutamic-pyruvate transaminase was 43% higher (P<.05) for the urea-fed lambs than for those fed soy protein. Copyright © 1972. American Society of Animal Science. Copyright 1972 by American Society of Animal Science.

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