草鱼鱼种对饲料中缬氨酸需求量的研究

以鱼粉和晶体氨基酸为蛋白源,制作7组缬氨酸梯度水平分别为6.3、7.2、8.9、11.0、12.6、14.1、15.8 g/(kg干饲料)的等氮等能半精制饲料,饲喂初始体质量为1.35 g的草鱼鱼种75 d,结果表明:草鱼鱼种增重率随饲料缬氨酸水平的提高而显著增加,当饲料缬氨酸水平达12.6 g/(kg干饲料)时草鱼鱼种增重率达最大值,继续增加饲料缬氨酸水平,草鱼鱼种增重率显著下降(P0.05)。草鱼鱼种蛋白质累积率表现出与增重率相同的趋势。草鱼鱼种饲料效率在饲料缬氨酸水平为12.6、14.1 g/(kg干饲料)时达最大值(P0.05)。饲料缬氨酸水平对草鱼鱼种鱼体必需氨基酸、支链氨基酸、总氨基酸含量及体组成无显著影响(P0.05)。草鱼鱼种肝脏谷丙转氨酶活性在饲料缬氨酸水平为11.0 g/(kg干饲料)时达最高值(P0.05),但各组之间并无明显规律性,饲料缬氨酸水平对草鱼鱼种肝脏谷草转氨酶活性无显著影响(P0.05)。分别以鱼体增重率、蛋白质累积率和饲料效率为指标,以抛物线回归模型分析,求得草鱼鱼种对饲料缬氨酸的需求量为12.79~13.68 g/(kg干饲料),占饲料蛋白的3.76%~4.02%。

Dietary valine requirement for juvenile grass carp (Ctenopharyngodon idella)

A 75d feeding trail was conducted to determine the dietary valine requirement for juvenile grass carp (Ctenopharyngodon idella). Seven isonitrogenous diets with graded levels of valine ranging from 6.3 to 15.8 g/kg of dry diet were fed to triplicate groups of fish with an average initial body weight of 1.35 g, respectively. The results showed that the weight gain rate, feed efficiency and protein retention efficiency were significantly affected(P<0.05). Weight gain rate and protein retention increased significantly with increasing dietary valine levels from 6.3 to 12.6 g/kg, but decreased significantly with further increase to 15.8 g/kg. Feed efficiency increased significantly with increasing dietary valine levels from 6.3 to 12.6 g/kg, but kept stable with increase to 15.8 g/kg. Fish essential amino acids, leucine, isoleucine, total amino acids and whole fish content were not affected significantly by dietary valine levels (P>0.05). ALT (glutamic-pyruvic transaminase) activity in hepatopancreas reached the maximum value at the dietary valine level of 11.0 g/kg, but there was no significant difference between the groups. AST (glutamic-oxalacetic transaminase) activity in hepatopancreas was not affected significantly by dietary valine levels (P>0.05). Second-degree polynomial regression analysis based on weight gain rate, protein retention efficiency and feed efficiency indicated that the requirements of dietary valine for fingerling grass carp were 12.79-13.68 g/kg of dry diet, 3.76%-4.02% of dietary protein, respectively.