大口黑鲈幼鱼对饲料中锌的需求量

为确定大口黑鲈幼鱼对饲料锌的适宜需求量,以酪蛋白、明胶和鱼粉为主要蛋白质源,以ZnSO_4·H_2O为锌源制作半精制基础饲料,分别向基础饲料中添加0、25、50、100和200 mg/kg锌,制成5种含不同锌水平饲料(24.8、48.8、78.9、126.1和223.6 mg/kg干物质)(命名为Zn-25、Zn-49、Zn-79、Zn-126和Zn-224),投喂初始体质量为(10.99±0.07) g的大口黑鲈幼鱼8周。结果显示,饲料中补充25 mg/kg锌(Zn-49)显著提高了大口黑鲈增重率,降低了饲料系数,进一步提高锌的添加量后,各组增重率和饲料系数趋于稳定。当饲料锌含量为25～49 mg/kg时,T-SOD和CuZn-SOD活性增加,锌含量达到49 mg/kg后,其活性保持基本稳定,而AKP活性在Zn-79组最高。大口黑鲈全鱼和脊椎骨中的锌含量随饲料中锌含量的增加而上升,当饲料锌含量达到126 mg/kg (Zn-126)后,全鱼和脊椎骨中的锌含量不再显著增加,而全鱼铁、骨铁、骨锰含量和全鱼铁、锌沉积率则随饲料锌含量的增加而下降。研究表明,在半精制饲料中补充锌可以显著改善大口黑鲈的生长和饲料利用,提高血清免疫能力、全鱼锌和骨锌的沉积,以增重率、饲料系数、全鱼锌和骨锌为指标,基于折线模型确定大口黑鲈幼鱼对饲料中锌的需求量分别为45.5、44.6、121.8和130.5 mg/kg干物质。

Dietary zinc requirement of juvenile largemouth bass (Micropterus salmoides)

To determine the dietary zinc requirement of juvenile largemouth bass (Micropterus salmoides), casein, gelatin and fish meal were used as the main protein sources and ZnSO₄·H₂O as zinc source to produce a semi-purified diet. Then, zinc was added into the basal diet at levels of 0, 25, 50, 100 and 200 mg/kg, to obtain five diets containing zinc of 24.8, 48.8, 78.9, 126.1 and 223.6 mg/kg dry matter, respectively. Largemouth bass with initial body mass of (10.99±0.07) g were fed one of the five diets for 8 weeks. The results showed that the supplementation of 25 mg/kg Zn significantly increased the weight gain rate (WGR), and reduced feed coefficient ratio (FCR) of largemouth bass, which tended to stabilize when higher levels of Zn were added. When dietary Zn reached 25-49 mg/kg, the serum activity of CuZn-SOD and T-SOD remained stable, while Zn-79 group showed the highest AKP activity. The zinc content in whole fish and vertebrae increased with the increasing dietary Zn, and showed no significant increase when dietary Zn content was higher than 126 mg/kg (Zn-126 group). The iron content in whole body, iron and manganese contents in vertebra, and the retention of iron and zinc in whole body decreased with the increasing dietary Zn. In conclusion, the supplementation of Zn in diet improved the weight gain and feed utilization, promoted serum immunity and Zn deposit in whole body and vertebra. Based on the WGR, FCR, whole body zinc and vertebra zinc, the broken-line analysis indicated that the dietary requirement of Zn was 45.5, 44.6, 121.8 and 130.5 mg/kg dry matter, respectively.