Microbial phytase improves amino acid utilization in young chicks fed diets based on soybean meal but not diets based on peanut meal

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Abstract
Studies were conducted to evaluate the ability of supplemental microbial phytase to improve performance of young chicks fed phytate-containing, amino acid-deficient diets. Diets based on corn and peanut meal or soybean meal (SBM) and dextrose were fed to young chicks housed in battery cages for 10- and 13-d experimental periods. Assays were designed to evaluate phytase supplementation of both amino acid-deficient and amino acid-adequate diets. Weight gain, feed intake, and gain:feed values of chicks increased (P < 0.05) when deficient amino acids were serially supplemented to either the corn-peanut meal or SBM-dextrose diets. Phytase supplementation (600 and 1,200 U/kg) to the corn-peanut meal diet resulted in no significant differences in weight gain, feed intake, or gain:feed values of chicks when the diet was either deficient or adequate in amino acids. However, phytase supplementation (1,200 U/kg) produced significant increases (P < 0.05) in gain:feed values, but not weight gain, of chicks when they were fed the amino acid-deficient, but not the amino acid-adequate, SBM-dextrose diet. This gain:feed response to phytase supplementation of the amino acid-deficient SBM-dextrose diet occurred in both crossbred (New Hampshire x Columbian) and commercial (Ross x Hubbard) chicks. A digestibility assay was also performed using cecectomized roosters fed dehulled SBM containing three levels of phytase (0, 600, and 1,200 U/kg). When averaged across nine essential amino acids and cystine, true amino acid digestibility (TAAD) values were increased by approximately 2% when 1,200 U/kg phytase was included with SBM and administered to cecectomized roosters. However, neither TAAD values nor TMEn were significantly improved by the phytase addition.