以酪蛋白和明胶为蛋白源,鱼油和豆油为脂肪源,糊精为糖源并添加氨基酸混合物配制精制基础饲料,通过向基础饲料中添加维生素A醋酸酯使饲料中的维生素A含量达到0、1 000、2 000、4 000、8 000和16 000 IU/kg(实测含量为245、1 005、1 835、3 781、7 583和15 273 IU/kg),配制出6种等氮等能的实验饲料(饲料1～6).以花鲈为实验对象,在室内流水系统中进行为期9周的生长实验,探讨精制饲料中不同维生素A含量对花鲈生长和血清学生化指标的影响.结果表明:摄食不添加维生素A组(饲料1)饲料的花鲈在养殖后期表现出较高的死亡率,并出现眼球浮肿、膨胀、鳍基充血以及鳃盖扭曲等维生素A缺乏症,而在其他维生素A添加组(饲料2～6)并未出现类似症状.体成分分析表明:饲料中不同维生素A含量会显著增加花鲈体脂肪含量,但对蛋白质和水分的含量没有显著影响.对花鲈血清指标分析表明:饲料添加维生素A含量会显著增加花鲈血清碱性磷酸酶(AKP)、甘油三酯(TG)和胆固醇(TC)含量,但显著降低丙氨酸氨基转移酶(ALT)和天冬氨酸氨基转移酶(AST)活力.采用折线模型,当以增重率为评价指标时,花鲈对饲料中维生素A的需求量为1 934.8 IU/kg;当以肝脏维生素A含量为评价指标时,花鲈对饲料中维生素A的需求量为3 546.6 IU/kg.

A 9-week feeding experiment was conducted to evaluate the effect of dietary vitamin A level on growth and serum biochemical parameters for juvenile Japanese seabass,Lateolabrax japonicus.Six groups of isonitrogenous(43% crude protein)and isoenergetic(20 kJ/g dry matter)purified diets(Diets 1-6)containing 245,1 005,1 835,3 781,7 583 and 15 273 IU vitamin A(supplied as retinyl acetate)per kg diet were fed twice daily to triplicate groups(10 fish/group)of fish[initial weight(10.20±0.14)g/fish]in 120 L plastic tanks.Fish fed the basal diet(Diet 1)developed heavy mortality,exophthalmos,haemorrhages at the base of the fins and distortion of operculum.None of these deficiency signs were observed in fish fed the vitamin A supplemented diets(Diet 2-6).Carcass lipid content significantly increased with dietary increasing vitamin A level,while protein and moisture showed no significant differences.The analyses of serum parameters showed that the activity of alkaline phosphatase(AKP),the content of triacylglycerol(TG)and total cholesterol(TC)all significantly increased with the increase of dietary vitamin A level,while the activities of glutamate transaminase(ALT)and aspartate aminotransferase(AST)had the reverse trend.Broken-line regression analysis of weight gain or liver vitamin A content showed that juvenile Japanese seabass require a minimum of 1 934.8 IU vitamin A/kg diet for maximal growth or 3 546.6 IU vitamin A/kg diet for maximal liver vitamin A deposition.

国家自然科学基金(30901108)