军曹鱼幼鱼日粮锌最适添加量的研究

在以卵白蛋白为蛋白源的基础饲料（Zn含量为5．65mg／kg）中添加10、20、30、40、50mg／kg以ZnSO4为Zn源的Zn，使饲料中总Zn含量为15．97、25．66、33．90、45．85、55．88mg／kg。投喂军曹鱼幼鱼8周。试验结果表明，基础饲料组鱼出现生长不良、厌食、皮肤糜烂和白内障等症状，其成活率、增重率、血清碱性磷酸酶活性（AKP）显著低于添加Zn组（P〈0．05），骨骼、肌肉、血清和肝脏Zn含量也表现出相同趋势。10mg／kg和20mg／kgZn添加量组鱼仍出现缺Zn症状，各项测定指标随Zn添加量的增加而增大。当饲料中Zn添加量达到30mg／kg时，各项指标趋向稳定，与添加量40mg／kg和50mg／kg组无显著差异。以增重率和骨骼Zn含量为主要评价指标，通过回归分析表明，以ZnSO4为Zn源时，军曹鱼幼鱼日粮Zn的最适添加量为42．86mg／kg。

Dietary Zinc Requirement of Juvenile Cobia (Rachycentron canadum)

The dietary zinc(10,20,30,40 and 50 mg/kg) was added to the purified diet(znic content 5.65 mg/kg) based on albumin as the protein source,in order to meet the dietary zinc content of 15.97,25.66,33.90,45.85 and 55.88 kg/mg.The feeding trial on cobia(Rachycentron caradum) was conducted for eight weeks.The results showed that there were no significant differences in feed conversion rate on cobia fed the experimental diets regardless of concentration of supplemental zinc compared to fish fed the basal diet;but the survival rate,weight gain rate and serum alkaline phosphatase(AKP) activity were significantly affected by dietary zinc level(P<0.05),there was a significant difference in zinc concentrations in muscle,bone,liver and serum for the fish fed the distinct zinc supplementation levels(P<0.05).The survival rate,weight gain rate,serum alkaline phosphatase activity and zinc concentrations in fish tissues and serum were responded in broken-lines models to increase in dietary zinc levels.Over signs of zinc deficiency such as slow growth,anorexia,erosive skin,cataract and increased mortality were observed in fish fed the low-zinc diet.Determined by broken-lines regression analysis,with zinc sulfate as the zinc sources,the minimum requirement for dietary zinc was recommended for 42.86 mg/kg.