1. Appetite suppressant activity of supplemental dietary amino acids and subsequent compensatory growth of broilers

Department of Poultry Science, The Pennsylvania State University, University Park 16802, USA. nap2@psu.edu

This study was conducted to take advantage of the appetite-suppressant effect of excessive dietary amino acids in reducing feed intake and, in turn, restricting the early rapid growth of broilers to minimize metabolic disorders. Dietary amino acids were supplemented to a basal diet to yield a total of 1.57, 2.57, and 3.57% His; 2.7, 4.3, and 5.9% Lys; 1.36, 2.16, and 2.96% Met; 2.8, 3.8, and 4.8% Thr; and 1.27, 2.27, and 3.27% Trp and were fed to 408 chicks from 4 to 11 d of age. Fifteen dietary treatments of His, Lys, Met, Thr, and Trp were compared to the basal diet. Feed consumption was measured daily. Body weight measurements were taken at 0, 4, 7, 11, 14, and 21 d. At 21 d, pectoralis major and minor muscles, liver, and abdominal fat pad were weighed. High levels of Met and His caused the greatest depression in appetite from 4 to 11 d, and Thr, Trp, and Lys were found to be less potent. The exponential growth rate (EGR) of birds from 4 to 11 d of age was significantly reduced by the intermediate and high levels of the amino acid supplementation. From 11 to 14 d, EGR was greatest with high levels of Met or Trp, indicating more potential compensatory growth realized with these treatments. The high level of His decreased the percentage of pectoralis minor muscle yield, whereas the high level of Lys and Met increased the percentage of liver compared to those fed the basal diet. These results indicate that it is possible to use excessive individual amino acids in diets to suppress the appetite and early rapid growth to alleviate or minimize metabolic disorders.

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