Use of Plasma Urea Nitrogen to Vary Protein Allowances of Lambs

Abstract

Three experiments were conducted with growing lambs to determine if plasma urea nitrogen (PUN) levels could be manipulated by dietary protein in such a way that desired PUN levels could be maintained over time and to ascertain whether or not the control of PUNs within a suitable range would result in improved performance. The data indicate that if animals are segregated on the basis of PUN levels after being fed a standard diet for 21 days and then fed a protein level designed to maintain PUN at about 15 mg/100 ml, superior performance will result. The desired PUN level was easier to achieve in individually fed lambs than in lot fed groups. The combined experiments demonstrate that PUN levels in individual lambs can be controlled and that initial PUN can be used to allocate lambs to controlled levels of dietary protein intake and thereby increase their performance. By careful stratification of the lot fed animals, it should be possible to maintain the desired levels throughout a feeding period and obtain superior gains with less dietary protein than if animals are fed without consideration of PUN levels.