实用饲料中添加结晶蛋氨酸对罗非鱼生长、体组成的影响

INFLUENCE OF PRACTICAL DIET SUPPLEMENTATION WITH FREE D-METHIONINE ON THE GROWTH AND BODY COMPOSITION IN TILAPIA OREOCHROMIS NILOTICUS×O.AUREUS

以奥尼罗非鱼(Oreochromis niloticus×O.aureus)为实验材料,在室内循环玻璃水族箱内分别饲喂含蛋氨酸为0.45%、0.50%、0.55%、0.60%和0.65%的等能等氮的实用饲料(胱氨酸为0.52%),日投喂率为体重的4%—8%,每日人工投饲三次,探讨实用饲料中添加结晶D-蛋氨酸(0.00%、0.05%、0.10%、0.15%和0.20%)对奥尼罗非鱼生长以及体组成的影响。结果表明:实用饲料中补充结晶D-蛋氨酸,罗非鱼的瞬间生长率(SGR)、饲料系数(FCR)、蛋白沉积率(APR)和肝脂含量均得到明显改善(p<0.05)。蛋氨酸0.50%水平显著提高了血清蛋氨酸的含量(p<0.05),但是对体蛋白含量和鱼体氨基酸含量均无显著影响(p>0.05)。结晶蛋氨酸能够被罗非鱼有效利用,是补充饲料蛋白质的一种有效途径。

Tilapia is the most commercially cultured species in the South China,and the culture scale has rapidly developed in the past few years.Due to high cost and limited availability,the replacement of fish meal by plant protein sources is of great interest.It is very important aspects that how to improve the utilization of plant protein sources in aquafeeds.Therefore,the aim of the present study was to investigate the effects of dietary supplementation with methionine on growth,body composition and levels of serum amino acids in juvenile hybrid tilapia.The tilapia Oreochromis niloticus×O.aureus（mean weight of（4.18±0.04）g） were fed separately in 15 fiberglass tanks（400 L） with 30 fish per tank.Five isonitrogenous and isoenergetic diets（crude protein 32%,gross energy 15.8 kJ/g） were formulated,in which free amino acids were supplemented by free D-methionine at 0.00%,0.05%,0.10%,0.15% and 0.20%,respectively.Every experimental diet was taken three repeats,and fed practical diets containing methionine 0.45%,0.50%,0.55%,0.60% and 0.65%（containing cystine 0.52%） thrice a day for 60 days at 4%—8% of body weight respectively.Results indicated that the practical diets containing free methionine improved the specific growth rate（SGR）,feed conversion ratio（FCR）,apparent protein retention（APR） and hepatopancreas lipid content in comparison with the basal diet（p〈0.05）.Specific growth rate（SGR） of fish fed diets containing methionine 0.55% was significantly higher than those in fish fed other diets（p〈0.05）.The highest feed conversion ratio（FCR） was observed in fish fed the diet containing methionine 0.55%（p〈0.05）.Significantly higher the concentration of serum free methionine was observed in juvenile hybrid tilapia fed diet with methionine 0.50% level than those of fish fed with other diets（p〈0.05）.There were no significant differences in condition factor,whole body moisture,protein,lipid,ash and body amino acids contents of tilapia among the five groups（p〉0.05）.Viscera ratio and hepatosomatic index decreased significantly with increasing methionine supplementation level（p〉0.05）.The results suggested that methionine supplementation can significantly improved growth performance in juvenile hybrid tilapia.Free methionine was proved to be a significantly better way of dietary protein supplementation.