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University of Illinios, Urbana 61801
2 Reprint requests should be addressed to this author at Dept. of Anim. Sci. 318 Mumford Hall, 1031 W. Gregory Drive, Urbana, IL 61801.
Abstract
Fifteen gravid, crossbred gilts were utilized in an experiment to measure the effect of five isonitrogenous dietary treatments (12% crude protein, sorghum-soybean meal; sorghum; sor-ghum+lysine; sorghum+threonine; sorghum+ lysine+threonine) on N balance, colostrum composition and plasma constituents (protein, urea N and IgG). All gilts were fed a standard corn-soybean meal diet from breeding until switched to the sorghum basal diet, on d 60 of gestation. Treatment diets were imposed at d 70. Nitrogen retention, measured between d 103 and 113 of gestation, was improved (P<.002) by lysine addition. Nitrogen retention was similar (P<.10) for gilts fed either the 12% crude protein, sorghum-soybean meal diet or the lysine + threonine-supplemented diet. Plasma protein levels at farrowing were depressed (P<.06) in those gilts fed sorghum diets without supplemental lysine and plasma urea N was elevated (P<.10). Plasma protein and plasma urea N were not affected by threonine supplementation (P<.10). In contrast, the depression of plasma IgG was ameliorated (P<.03) by threonine and unaffected by lysine supplementation. These results confirm the hypothesis that lysine is the first limiting amino acid in sorghum protein for gravid gilts as determined by N retention but indicate that threonine is likely the first limiting amino acid for the production of the specific protein, IgG.
1 Supported by a Fellowship from Consejo Nacional de Ciencia y Tecnologia, Mexico, D.F.
3 The assistance of Scott Williamson, Howard Cook, Dale Alexander, Ron Brewer and Steve Heffernan with diet preparation and animal care is gratefully acknowledged.
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