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Growth and Carcass Characteristics of Broilers Fed Low-Protein, Threonine-Supplemented Diets

Nutri-Quest, Inc., 1400 Elbridge Payne Road, Chesterfield, MO 63017; Phone: (314) 537-4057; FAX: (314) 532-1710

J. D. Firman and S. D. Boling

Animal Sciences Center, University of Missouri, Columbia, MO 65211

Correspondence: M. T. Kidd

For years poultry nutritionists have decreased the use of protein-rich feedstuffs by adding methionine and lysine. The extent to which crude protein can be decreased without compromising bird performance remains subject to much debate. Because Threonine is the third limiting amino acid for broilers, two experiments were conducted to evaluate Threonine's efficacy in low crude protein diets adequate in methionine and lysine.

In Experiment 1, Threonine supplementation to low crude protein diets improved some carcass measurements at 56 days of age although it failed to do so at 42 days of age. In Experiment 2, birds fed a low crude protein diet containing supplemental Threonine had 21- to 42-day weight gain and feed conversion statistically equivalent to that of those fed a high crude protein diet. Low crude protein diets containing Threonine-limiting ingredients may require supplemental L-Threonine for optimal feed conversion and weight gain. Poultry nutritionists who formulate low crude protein broiler diets with Threonine-limiting ingredients should pay careful attention to the level of dietary Threonine to optimize feed conversion ratios and monetary returns.

Key Words: Amino acid • broiler • feed conversion • low crude protein • Threonine