Digestible protein requirement for Nile tilapia fed with rations based on soybean meal and corn

ABSTRACT. The objective was to determine the requirement of digestible protein (DP) for Nile tilapia fed with diets based on soybean meal and corn. Two hundred Nile tilapia juveniles, sexually reversed, were used for a trial period of 100 days. The animals were distributed in 20 boxes of 1000 L-1 in a random design with five treatments and four replications, the boxes were connected to a water recirculation system. Five isoenergetic diets were tested with different levels of digestible protein (DP): 20, 25, 30, 35 and 40%. At the end of the experimental period were evaluated the zootechnical performance data. A quadratic effect (p < 0.05) was shown to parameters of final weight, weight gain, final length, fillet yield and visceral fat with the best points that ranged from 28.3 to 29.9% of DP. The largest area of hepatocytes was found to the lowest levels of DP in the diet (20 and 25%) compared to the other levels, which were similar. Thus, Nile tilapia has adequate performance for the consumption of diets based on soybean and corn meal and the recommended level is 28.3% of PD in these conditions.

摘要
本试验旨在确定以豆粕和玉米为基础饲料的尼罗罗非鱼对可消化蛋白质（digestible protein，DP）的需求量。试验选取200尾性逆转尼罗罗非鱼幼鱼，试验周期为100天。将试验鱼随机分配至20个容积为1000升的养殖箱中，采用5个处理组、4个重复的随机试验设计，所有养殖箱均连接水循环系统。本试验共设置5种等能饲料，其可消化蛋白质水平分别为20%、25%、30%、35%和40%。试验结束后，测定各组试验鱼的养殖性能指标。结果显示，终体重、增重、终体长、鱼片出肉率及内脏脂肪含量均呈现显著二次效应（p<0.05），最优可消化蛋白质水平区间为28.3%~29.9%。与其余各组相比，饲料可消化蛋白质水平最低的20%和25%组的肝细胞面积最大，其余各组肝细胞面积无显著差异。综上，以豆粕和玉米为基础饲料饲喂尼罗罗非鱼可获得良好养殖性能，本试验条件下推荐可消化蛋白质水平为28.3%。