金鼓鱼幼鱼对蛋白质的适宜需要量研究

Studies on requirement of optimal protein levels in diets of butterfish Scatophagus argus juvenile

为确定金鼓鱼（Scatophaus Jargus）日粮中蛋白质的适宜添加量，作者以酪蛋白为蛋白源、鱼油为脂肪源，配制脂肪水平为8％，蛋白水平分别为24％、28％、32％、36％、40％的5种配合饲料（D1-D5）．在海上网箱中以初始体质量为4.3g左右的幼鱼开展养殖实验。8周后，测定实验鱼增质量率、特定生长率、蛋白质效率、饲料系数、消化酶和一些免疫及抗氧化指标。结果显示，随着饲料蛋白水平的升高，金鼓鱼的增质量率、特定生长率、蛋白质效率等均呈现先上升后下降的趋势，以D3组最高，3项指标均显著高于Dl、D2组；饵料系数呈现先下降再上升趋势，以D3组最低，且显著低于D1、D2组。饲料蛋白水平也显著影响金鼓鱼的相关生理生化指标，其中D3和D4组的全鱼蛋白含量、消化道蛋白酶活性和一些免疫抗氧化指标最高，全鱼脂肪含量最低。根据饲料蛋白含量与增质量率的线性回归分析，确定金鼓鱼幼鱼饲料中的适宜蛋白水平为35％。

In order to determine the requirement of optimal protein levels for butterfish Scatophagus argus, five formulated feeds （D1-D5） containing 8% lipid and different levels of protein （24%, 28%, 32%, 36% and 40%） were prepared using casein as protein source and fish oil as lipid source. After an 8-week feeding period of butterfish juveniles （average body weight 4.3 g） in net cages in the sea, the effects of dietary protein levels on growth performance and physiological/biochemical indexes of butterfish juveniles were evaluated. The results showed that the weight gain rate （WGR）, specific growth rate （SGR） and protein efficiency rate （PER） upgraded first and then declined with the increase of dietary protein levels, and the maximum value was observed in the group of fed with D3, which was significantly higher than those in dietary D1 and D2 groups. However, the feed conversion ratio （FCR） displayed an opposite changing tendency, and the minimum value was observed in D3 group which was significantly lower than those in D1 and D2 groups （P〈0.05）. The dietary protein levels also signifi- cantly affected the contents of lipid and protein in fish body, the activities of protease in digestive system, and the immunity and antioxidant indexes in fish body. All the vales were largest in D3 and D4 dietary groups. According to the quadratic equa- tion of WGR with dietary protein levels, the suggested optimal dietary protein level is about 35% for butterfish juveniles.