吉富罗非鱼对饲料精氨酸的需要量

以饲料精氨酸水平分别为0.67%、0.94%、1.24%、1.58%、1.86%和2.11%的6种等氮等能的半纯化饲料(粗蛋白质含量30.21%,总能17.77 MJ/kg),投喂初始体重为(81.52±2.00)g的吉富罗非鱼60 d,考察饲料精氨酸水平对吉富罗非鱼生长性能、饲料利用、体成分、血清生化指标和非特异性免疫指标的影响,以期获得吉富罗非鱼对饲料精氨酸的最佳需要量。每种饲料投喂3个网箱,每个网箱放养15尾鱼。结果表明:随着饲料精氨酸水平的升高,吉富罗非鱼的增重率、特定生长率、蛋白质效率以及蛋白质沉积率均呈现先上升后下降的趋势,并均在1.58%组达到最高值,与其他组差异显著(P0.05);饲料系数、肝体比、脏体比则呈现先下降后上升的趋势,饲料系数在1.58%组达到最低值,与其他组差异显著(P0.05);全鱼粗脂肪和肌肉粗灰分含量的变化趋势与饲料系数相似,肌肉粗脂肪呈现与增重率和特定生长率相似的变化趋势,而全鱼粗灰分和肌肉粗蛋白质含量则呈先上升后稳定的趋势。饲料精氨酸水平对吉富罗非鱼的肥满度,全鱼水分、粗蛋白质及肌肉水分含量无显著影响(P0.05)。肌肉中各氨基酸(除酪氨酸、甘氨酸、丙氨酸外)、必需氨基酸、总氨基酸含量均随饲料精氨酸水平的升高呈先上升后下降的趋势。饲料精氨酸水平显著影响血清中谷草转氨酶、谷丙转氨酶活性及总胆固醇、甘油三酯、总蛋白、尿素氮和葡萄糖含量(P0.05),也显著影响肝脏和血清中总超氧化物歧化酶、总一氧化氮合酶和溶菌酶的活性(P0.05)。以增重率、饲料系数和蛋白质效率为主要评价指标,通过二次回归分析可知,吉富罗非鱼对饲料中精氨酸需要量为1.51%~1.58%,占饲料蛋白质的4.99%~5.25%。

Dietary Arginine Requirement of Genetically Improved Farmed Tilapia (Oreochromis niloticus)

This experiment was conducted to study the effects of dietary arginine ( Arg) level on growth per?formance, feed utilization, body composition, serum biochemical indices and non?specific immune indices of genetically improved farmed tilapia ( GIFT, Oreochromis niloticus) , in order to determine the dietary Arg re?quirement of GIFT. Six isonitrogenous and isoenergetic semipurified diets ( contained 30.21% crude protein and 17.77 MJ/kg gross energy) were formulated with 0.65%, 0.94%, 1.24%, 1.58%, 1.86% and 2.11% Arg, respectively. Each experimental diet was fed to 3 net cages for 60 d, and 15 fish with the initial body weight of (81.52±2.00) g in each net cage. The results showed as follows: with the dietary Arg level increasing, the weight gain rate ( WGR) , specific growth rate ( SGR) , protein efficiency ratios ( PER) and protein deposition efficiency ( PDE) were firstly increased and then decreased, and reached their peaks in the 1. 58% group, which were significantly higher than those in other groups ( P<0. 05 ); whereas the feed conversion ratio ( FCR) was firstly decreased and then increased, and reached the lowest value in the 1.58% group, which was significantly lower than that in other groups ( P<0.05);the hepatosomatic index ( HSI) and viscerosomatic in?dex ( VSI) had the same trend with FCR. The change tendency of ash content in muscle and crude lipid content in whole body was similar to FCR with dietary Arg level increasing, but the change tendency of crude lipid content in muscle was similar to WGR and SGR, while the crude protein content in muscle and ash content in whole body were firstly increased with dietary Arg level increasing and then leveled off. Dietary Arg level had no significant effects on the condition factor ( CF) and the contents of crude protein in whole body, moisture in whole body and muscle ( P>0.05) . With the increase of dietary Arg level, the contents of all amino acids ( ex?cept tyrosine, glycine and alanine), essential amino acids and total amino acids in muscle were firstly de?creased and then increased. Dietary Arg level significantly affected the activities of aspartate transaminase ( AST) , alanine aminotransferase ( ALT) and the contents of total protein ( TP) , urea nitrogen ( UN) , total cholesterol ( T?CHO) , glucose ( GLU) and triglycerides ( TG) in serum ( P<0.05) , and significantly affected the activities of total superoxide dismutase ( T?SOD ) , total nitric oxide synthase ( T?NOS ) and lysozyme (LYZ) in liver and serum (P<0.05). Regarding the WGR, FCR and PER as the evaluation indicators, the quadratic regression analysis shows that the dietary Arg requirement of GIFT is 1. 51% to 1. 58% of diet or 4.99% to 5.25% of dietary protein.