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چکیده
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A study was conducted to evaluate the effects of adding Gly to broiler starter diets in which the CP was decreased from 24 to 18% by adding essential amino acids. Effects on live performance, development of the digestive organs, and bone and some serum parameters were evaluated. Male broiler chicks were fed from hatch to 18 d on 1 of 14 experimental diets in which amino acids were added in turn as they became limiting. The order of limiting amino acids was Met (TSAA), Lys, Thr, Val, Ile, Arg, Trp, and His. For diets supplemented with Thr through His, aliquots of the diets were supplemented with Gly to provide 2.0% Gly + Ser. Each treatment was fed to 6 pens of 5 male chicks of a commercial strain. The BW and FCR of broilers fed diets in which Arg, Trp, and His became limiting were significantly lower than those of birds fed diets in which Met and Lys were limiting. The addition of Gly significantly improved the BW and FCR of broilers fed the diets in which Arg, Trp, and His became limiting and significantly improved the FCR of diets in which Val became limiting. Significant differences were observed in relative organ weights between chicks fed the diets in which Thr, Val, and Ile became limiting and those fed the diets with Met and Lys added. Addition of Gly to some diets significantly increased or decreased the relative weights of the various intestinal segments, but not in a consistent manner. Significant differences were observed for tibia ash, tibia diameter, and bone-breaking strength of broilers among the broilers fed the diet of limiting amino acids and those fed only Met and Lys. Supplementation with Gly increased bone-breaking strength and the diameter of the tibia. No significant differences were observed for urea nitrogen, ammonia, and blood urea nitrogen levels in the serum of broilers fed the diets with the first 8 limiting amino acids. Supplemental Gly significantly increased the serum urea nitrogen and serum ammonia content. Therefore, Gly may be crit
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