Threonine Requirement of Growing and Finishing Swine Fed Sorghum-Soybean Meal Diets

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Abstract
Two experiments (one with growing pigs, 17.7 kg initial weight and one with finishing pigs, 58.9 kg initial weight) were conducted to determine the threonine requirement in sorghum-soybean meal diets. Four barrows and four gilts were individually fed one of six isonitrogenous sorghum-soybean meal diets formulated with a stepwise addition (.06%) of L-threonine. Soybean meal was restricted to ensure that threonine was deficient in the basal diets (.39 and .29% in the growing and finishing diets, respectively). All other essential amino acids were present to provide 110% or more of the requirement based on the 1973 National Research Council estimates of minimum requirements for 16% protein grower and 14% finisher diets. An equimolar glycine-L-glutamic acid mixture was added to obtain the 16% grower and 14% finisher diets. In the growing experiment, average daily gain (g) and gain/feed (g/kg) for dietary L-threonine levels of .39, .45, .51, .57, .63 and .69% were, respectively: 518, 371; 622, 426; 620, 422; 619, 439; 615, 429 and 594, 416. Spline regression analyses showed that the level of threonine needed to optimize average daily gain and gain/feed in the 16% protein sorghum-soybean meal grower diets was .47%. Average daily gain and gain/feed (finishing experiment) resulting from dietary L-threonine levels of .29, .35, .41, .47, .53 and .59% were, respectively: 602, 219; 725, 244; 713, 242; 761, 237; 742, 241 and 807, 236. The level of threonine needed to optimize average daily gain and gain/feed in a 14% protein sorghum-soybean meal diet was .39 and .37%, respectively. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.

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