关键词: 酵母水解物, 肉鸡, 代谢能, 氨基酸消化率

Abstract:

【Objective】 The purpose of this study was to evaluate the apparent metabolic energy, nitrogen-corrected apparent metabolic energy, ileal apparent amino acid digestibility, standard ileal amino acid digestibility and total intestinal apparent amino acid digestibility of yeast hydrolysate in broilers, so as to provide the reference for the wide application of yeast hydrolysate in broiler diets. 【Method】 A total of 160 Cobb white-feathered broilers at 18 days old with no difference in body weight were randomly divided into the control group and experimental group. There were 8 replicates in each group, and 10 chickens with half male and half female were in each replicate. The control group was fed a nitrogen-free diet consisting of corn starch, glucose, fiber and soybean oil, and the experimental group was fed a semi-homozygous diet using yeast hydrolysate as the sole crude protein source. Furthermore, the control group and the experimental group were fed with 0.5% titanium dioxide, respectively, as an exogenous indicator. During the whole experiment, free feeding was available for broilers, feces were collected on 22-24 days using total fecal collection method, and the feed intake of broilers was counted. Further, the apparent metabolic energy of yeast hydrolysate and nitrogen-corrected apparent metabolic energy were calculated by measuring the total energy and nitrogen content in both diets and feces of broilers. After26 days of experiment, the latter half of ileum was dissected under anesthesia, the chime was taken out, and the contents of amino acids and titanium dioxide in both diet and ileal chyme were measured to calculate the apparent amino acid digestibility, standard ileal amino acid digestibility and total intestinal apparent amino acid digestibility of yeast hydrolysate. 【Result】 (1) The total energy value of yeast hydrolysate was 18.19 MJ·kg ^-1, the apparent metabolic energy value was 11.22 MJ·kg ^-1, and the nitrogen-corrected apparent metabolic energy was 10.17 MJ·kg ^-1. Effective energy was equivalent to that of common soybean meal. (2) Crude protein content of yeast hydrolysate was 41.7%, and total amino acid was 36.97%. The ratio of essential amino acid to dispensable amino acid was 44:56, which was close to that of common soybean meal. The limiting amino acids of yeast hydrolysate were Met, Met+Cys, Arg, Leu, Ile, Phe+Tyr, Val, His, lys, Thr and Trp, which were different from soybean meal. (3) The ileal apparent amino acid digestibility, standard ileal amino acid digestibility and total intestinal apparent amino acid digestibility of yeast hydrolysate were all higher than 70%. The available limiting amino acids were Met, Met+Cys, Arg, Leu, Ile, Thr, Phe+Tyr, His, Lys, Val, and Trp. Methionine and arginine were the first and the second limiting amino acids, and leucine and isoleucine were the third and the fourth limiting amino acids, respectively. Threonine was poorly available, and was regarded as the fifth restrictive available amino acid. In addition, the limiting amino acids of yeast hydrolysate were quite different to soybean meal. 【Conclusion】 Yeast hydrolysate was a kind of protein feed material. Its protein content and effective energy value were similar to soybean meal, but its amino acid composition and availability were quite different to soybean meal. Therefore, in the application of yeast hydrolysate in broiler diet, it was necessary to consider the need of supplementing different amino acids or mixing different protein feeds to balance amino acids.

Key words: hydrolyzed yeast, broiler, metabolizable energy, amino acid digestibility