酵母水解物对吉富罗非鱼生长、免疫力、抗氧化性及抗无乳链球菌感染的影响

本研究旨在探究饲料中添加酵母水解物对吉富罗非鱼(Oreochromis niloticus)生长性能、免疫力和抗病力的影响。在基础饲料中添加0 (对照组)、0.5%、1.0%、1.5%和2.0%的酵母水解物制成5种实验饲料，对5组初始体重为(25.80±0.45) g的吉富罗非鱼进行为期8周的养殖实验，每组 3个重复，每个重复30尾鱼。实验结束后，每个重复选择12尾鱼进行无乳链球菌(Streptococcus agalactiae)攻毒实验，每尾鱼腹腔注射0.2 mL浓度为8.3×105 CFU/mL的菌液，连续观察14 d，统计累积死亡率。结果显示，随着酵母水解物添加量的增加，吉富罗非鱼终末体质量(FBW)和特定生长率(SGR)均呈先显著上升(P<0.05)后下降的趋势。回归分析表明，当SGR达到最大值时，对应的酵母水解物添加量为1.29%。罗非鱼血清一氧化氮合酶、酚氧化酶、酸性磷酸酶、过氧化氢酶和超氧化物歧化酶活性均随饲料中酵母水解物添加量的提高呈先上升后下降的趋势(P<0.05)，添加量为1.5%时达最大值。饲料添加酵母水解物对吉富罗非鱼无乳链球菌的抵抗力有显著影响(P<0.05)，除添加量为0.5%的实验组死亡率与对照组差异不显著外，其他实验组罗非鱼的死亡率均显著低于对照组(P<0.05)。本研究中，饲料添加酵母水解物可有效提高吉富罗非鱼的生长性能、免疫力和抗病力，且在添加量为1.5%时，效果最显著。

Effects of Yeast Hydrolysate on Growth, Immunity, Oxidation Resistance, and Anti-Streptococcus agalactiae Activity of Genetically Improved Farmed Tilapia

This study aimed to investigate the effects of yeast hydrolysate on the growth performance, immunity, oxidation resistance, and anti-Streptococcus agalactiae activity of genetically improved farmed tilapia (GIFT). Five experimental diets were prepared by adding 0 (control group), 0.5%, 1.0%, 1.5%, and 2.0% yeast hydrolysate to the basic diet of these fish. GIFT with an initial weight of (25.80±0.45) g were randomly divided into five groups and were cultured for 8 weeks. After the breeding test, 12 fish from each group were selected for the S. agalactiae challenge test. Each fish was injected intraperitoneally with 0.2 mL bacterial solution at a concentration of 8.3×105 CFU/mL, and the cumulative mortality was counted for 14 days. The results showed that the final body weight and specific growth rate (SGR) increased significantly at first (P<0.05) and then decreased with the increase in the concentration of yeast hydrolysate. Regression model analysis showed that the most suitable dietary yeast hydrolysate level reached the highest SGR at 1.29%. The activities of nitric oxide synthase, phenol oxidase, acid phosphatase, catalase, and superoxide dismutase increased (P<0.05) at first and then decreased under the increased dietary yeast hydrolysate level; the peak was reached on supplementation with 1.5% yeast hydrolysate. Dietary yeast hydrolysate significantly influenced the resistance of GIFT to S. agalactiae (P<0.05). Except for the 0.5% yeast hydrolysate test group, the cumulative mortalities of the other test groups (1.0% yeast hydrolysate supplementation or more) were significantly lower than the cumulative mortality of the control group (P<0.05). In this study, the addition of yeast hydrolysates to the diet of GIFT significantly improved their growth performance, immunity, and disease resistance, and the 1.5% yeast hydrolysate-supplemented test group showed the best results.