黄鳝幼鳝对饲料中锌需求量的研究

DIETARY ZINC REQUIREMENT OF JUVENILE MONOPTERUS ALBUS

  • 摘要: 为探究黄鳝(Monopterus albus)对锌的适宜需求量, 以鱼粉和豆粕为蛋白源, 鱼油和豆油为脂肪源配制基础实验饲料, 以甘氨酸锌(Zn2+≥21%)为锌源在基础饲料中分别添加0、10、20、40、80、160和320 mg/kg的锌, 制成7种不同锌水平的饲料(实际锌含量分别为48.24、60.79、70.25、88.04、123.88、204.35和381.65 mg/kg干物质), 饲喂初始体重为(23.17±0.04) g的黄鳝 60d, 以增重率、特定生长率、脊椎骨锌含量和血清碱性磷酸酶活性等指标综合评价黄鳝锌的需求量。结果表明: (1)各组的增重率、特定生长率随饲料锌水平呈先上升后下降趋势, 存活率呈下降趋势, 60.79组和70.25 mg/kg组黄鳝的增重率和特定生长率较高, 381.65 mg/kg组增重率、特定生长率和存活率均最低且显著低于48.24—70.25 mg/kg组, 以增重率和特定生长率为评价指标, 黄鳝幼鳝对锌的需求量分别为56.85和56.79 mg/kg。(2)随着饲料锌水平的升高, 全鱼粗蛋白含量呈先上升后下降趋势, 70.25 mg/kg组最高, 粗脂肪呈先下降后平缓的趋势, 48.24 mg/kg组显著高于其他组, 全鱼锌含量升高、锌沉积率呈先上升后下降的趋势, 黄鳝脊椎骨、肝脏、皮肤和肾脏中锌含量显著增加, 脊椎骨锌含量呈先显著上升后平缓的现象; 肌肉中锌含量变化不明显; 全鱼铁、锰、铜、骨铁和骨锰含量呈下降趋势, 骨磷和骨钙含量呈先上升后下降趋势, 以脊椎骨锌含量为评价指标, 黄鳝对锌的需求量为81.01 mg/kg。(3)随着饲料锌水平的升高, 黄鳝血清碱性磷酸酶活力和白蛋白含量呈先上升后下降的趋势, 在88.04 mg/kg组最高且显著高于204.35—381.65 mg/kg组, 以血清碱性磷酸酶活力为评价指标, 黄鳝幼鳝对锌的需求量为76.73 mg/kg。溶菌酶活力呈先上升后下降的趋势, 60.79 mg/kg组显著高于其他组, 381.65 mg/kg组血清谷丙转氨酶活性最高且显著高于48.24—70.25 mg/kg组。综合饲料锌水平对黄鳝生长性能、体成分、组织锌沉积和血清生化指标的影响, 黄鳝饲料中适宜的锌需求量为56.79—81.01 mg/kg。黄鳝皮肤、脊椎骨和肝脏较肌肉更易沉积锌。

     

    Abstract: In order to determine the optimal feed zinc requirement for Monopterus albus, we formulated basic experimental diets using fish meal and soybean meal as protein sources, and fish oil and soybean oil as fat sources. Seven experimental diet groups were created by sequentially adding glycine zinc as the zinc source to the basic group, resulting in zinc concentrations of 0, 10, 20, 40, 80, 160, 320 mg/kg. Monopterus albus with an initial body weight of (23.17±0.04) g were fed these diets for 60d, resulting in actual zinc contents of 48.24, 60.79, 70.25, 88.04, 123.88, 204.35, and 381.65 mg/kg dry matter, respectively. The zinc demand of Monopterus albus was comprehensively evaluated by weight gain rate, specific growth rate, vertebral bone zinc content and serum alkaline phosphatase activity. The results showed as follows: (1) The weight gain rate and specific growth rate initially increased and then decreased with dietary zinc level. Survival rate exhibited a declining trend. The 60.79 and 70.25 mg/kg groups showed higher weight gain and specific growth rates compared to other groups. The 381.65 mg/kg group had the lowest rates, significantly lower than the 48.24—70.25 mg/kg group. Based on gain rate and specific growth rate, the zinc demand for Monopterus albus was 56.85 and 56.79 mg/kg, respectively. (2) With increasing dietary zinc level, whole fish crude protein initially increased and then decreased, peaking in the 70.25 mg/kg group. Whole fish crude fat exhibited an initial decrease followed by a slowdown, with the 48.24 mg/kg group significantly higher than others. Zinc content in the whole body increased, and zinc deposition rate followed an initial increase and subsequent decrease. The content of zinc in various tissues (vertebrae, liver, skin and kidney) increased significantly, with vertebrae zinc content peaking before leveling off. Bone phosphorus and calcium content increased and then decreased. Considering zinc content in vertebral bone, the zinc demand for Monopterus albus was 81.01 mg/kg. (3) With the increase of dietary zinc level, Monopterus albus exhibited a pattern of initially increasing and subsequently decreasing serum alkaline phosphatase activity and albumin content. The apex of these parameters was observed in the 88.04 mg/kg group, surpassing significantly the range of 204.35—381.65 mg/kg. Utilizing serum alkaline phosphatase activity as the evaluation index, the zinc demand of Monopterus albus juveniles was determined to be 76.73 mg/kg. Lysozyme activity demonstrated an initial rise followed by a decline, with the 60.79 mg/kg group exhibiting a marked superiority over the other groups. The serum alanine aminotransferase activity in the 381.65 mg/kg group reached the highest levels, significantly higher than that in the 48.24—70.25 mg/kg group. In conclusion, considering the effects of dietary zinc levels on growth performance, nutrient composition, tissue znic deposition, and serum biochemical indexes of Monopterus albus, the appropriate zinc demand in the diet ranges from 56.79 to 81.01 mg/kg. Additionally, the skin, spine, and liver of Monopterus albus exhibit higher susceptibility to zinc deposition than muscle.

     

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