用饲料酵母替代鱼粉对大菱鲆幼鱼生长及免疫机能的影响

分别用质量分数为0、15%、30%、45%、60%的饲料酵母替代饲料中0、17%、34%、51%、68%的鱼粉,配制成5种等氮、等能的试验饲料,分别记为Ⅰ（对照组）、Ⅱ、Ⅲ、Ⅳ和Ⅴ组。将195尾大菱鲆Scophthatmus maximus（9.02 g±0.15 g）随机分为5组,每组设3个重复,每个重复组放养13尾鱼。将试验鱼饲养于设有循环流水系统的水族箱（60 cm×40 cm×50 cm）中,用5种饲料投喂,每天投喂3次,投饲率为鱼体质量的3%～4%,以生长及免疫指标来评价饲料酵母替代鱼粉对大菱鲆幼鱼生长的影响。经过56 d的饲养,结果表明：Ⅱ组的增重率（275.30%）和特定生长率（1.91%/d）最高,但与对照组（235.66%、1.82%/d）无显著差异（P〉0.05）;Ⅱ组的饲料系数（1.34）最低,但与对照组（1.53）无显著差异（P〉0.05）;Ⅱ组（97.44%）和Ⅳ组（94.87%）的成活率均显著高于对照组（84.62%）（P〈0.05）,而Ⅴ组的成活率（74.36%）则显著低于对照组（P〈0.05）;鱼体的粗蛋白含量随着饲料酵母替代比例的增加而逐渐降低（P〈0.05）,粗灰分则逐渐升高（P〈0.05）;溶菌酶、超氧化物歧化酶和血浆中蛋白的含量随着替代比例的增加而减少,且当饲料酵母替代比例超过51%时,与对照组差异显著（P〈0.05）。综合考虑大菱鲆的生长指标、形体指标、鱼体成分和免疫机能等因素,要获得最佳的养殖效益,大菱鲆幼鱼饲料中用饲料酵母替代鱼粉的比例以17%为宜。

Effects of replacement of fish meal by feed yeast on growth performance and immunity in turbot Scophthalmus maximus

Turbot Scophthalmus maximus with body weight of（9.02±0.15） g were randomly stocked into 15 glass tanks of each 60 cm ×40 cm × 50 cm with circulating sea water at a rate of 15 fish per tank and fed five isocaloric and isonitrogenous diets containing 0（Group Ⅰ）,15%（Group Ⅱ）,30%（Group Ⅲ）,45%（Group Ⅳ） and 60%（Group Ⅴ）of feed yeast,which replaced 0,17%,34%,51% and 68% of fish meal,at feeding rate of 3%-4% three times a day for 56 d.The results showed that there were the maximal weight gain rate（WGR）（275.30%）,and specific growth rate（SGR）（1.91%/d） and the minimal foodd conversion ratio（FCR）（1.34） in Group Ⅱ compared with the control group（235.66%,1.82%/d and 1.53）.The fish in Group Ⅱ（97.44%） and Group Ⅳ（94.87%）had significantly higher survival rate（SR） than that in the control group（84.62%）,but the fish in Group Ⅴ had significantly lower（74.36%）survival.Crude protein contents in the fish were decreased,and the ash contents in the fish were increased with the increase in the dietary yeast.Lysozyme activity,total protein content and superoxide dismutase（SOD） activity in plasma were found to be decreased with the increase in feed yeast,and significant differences for the parameters were observed in the fish fed the diets containing to upon 51% of the yeast.It is concluded that the optimal dietary yeast is 17% based on the growth performance,morphological indicators,body composition and immunity.