吉富罗非鱼对饲料中锌的需要量

Dietary zinc requirement of genetically improved farmed tilapia( GIFT,Oreochromis niloticus)

为考察吉富罗非鱼(GIFT,Oreochromis niloticus)对饲料中锌的需要量,以蛋氨酸锌为锌源,配制锌添加水平分别为0,10,20,40,80,160 mg/kg的6组等氮等脂饲料(实测值分别为9.98,21.47,33.75,56.03,88.16,172.54 mg/kg),饲喂初始体质量为(84.44±3.04)g的吉富罗非鱼,试验鱼分为6组,每组3个重复,每个重复20尾鱼,养殖周期为10周。结果显示,随着饲料中锌含量的增加,吉富罗非鱼的增重率、特定生长率先显著升高,在锌含量达到33.75 mg/kg后趋于稳定,添加锌显著降低了饲料系数,提高了成活率。饲料锌含量对全鱼水分、粗蛋白及灰分含量无显著影响,显著降低了全鱼粗脂肪含量。饲料中添加锌对血清总胆固醇含量无影响,显著提高了血清碱性磷酸酶的活性,碱性磷酸酶活性在锌含量达到33.75 mg/kg后趋于稳定,血清甘油三酯含量,乳酸脱氢酶、谷草转氨酶和谷丙转氨酶活性则呈下降趋势。饲料锌含量显著影响脊椎骨、全鱼和肝脏锌的含量,脊椎骨和全鱼锌含量先线性上升,在锌含量达到56.03 mg/kg后趋于稳定,各组的肌肉锌含量无显著差异。以增重率、骨骼锌和全鱼锌含量为评价指标,根据折线回归分析得出,以蛋氨酸锌为添加锌源,吉富罗非鱼对饲料中锌的需要量分别为32.37、55.67和56.13 mg/kg。

A feeding experiment was conducted to estimate the optimum requirement of dietary zinc for genetically improved farmed tilapia （ GIFT, Oreochromis niloticus） .The six experimental diets were formulated to contain the graded levels of zinc （0, 10, 20, 40, 80, 160 mg/kg, respectively） supplied as methionine zinc, providing the actual dietary zinc val-ues of 9.98（control）, 21.47, 33.75, 56.03, 88.16, 172.54 mg/kg diet, respectively.Each diet was assigned to three replicate groups of GIFT （ mean initial body weight： 84.44 ±3.04 g） for 10 weeks.Results indicated that weight gain rate （ WGR） , specific growth rate （ SGR） enhanced with dietary zinc levels up to 33.75 mg/kg diet , and plateaued thereafter .Fish fed with the control diet had significantly higher feed conversation rate （ FCR） and lower survival rates （ SR） than those fed on diets supplemented with zinc.Dietary zinc supplementation had no significant effect on the mois-ture, protein and ash contents of whole body .However, the lipid content of whole body in the control group was signifi-cantly higher than those of the other five groups .Serum total cholesterol （ TCHO） concentration showed no significant differences among the treatments.However, alkaline phosphatase （ ALP） activity increased with dietary zinc levels up to＆amp;nbsp;33.75 mg/kg diet .Serum triglyceride （TG） concentration, lactate dehydrogenase （LDH）, aspartate aminotransferase （ AST） and alanine aminotransferase （ ALT） activities declined with increasing dietary zinc levels.Zinc concentrations in vertebrae and whole body were linearly increased up to the 56.03 mg zinc per kg diet and then remained stable beyond this level.Liver zinc concentration increased with dietary zinc levels, but muscle zinc concentrations remained relatively stable.Linear regression analysis showed that the optimum dietary zinc requirement for GIFT, using WGR, vertebrae and whole body zinc concentrations as response criteria, was 32.37, 55.67 and 56.13 mg/kg, respectively.