生长中期草鱼蛋氨酸需要量的研究

Methionine Requirement of Grass Carp(Ctenopharyngodon idell) during Middle Growth Stage

本试验通过研究饲料蛋氨酸水平对生长中期草鱼生长性能和消化吸收能力的影响,旨在确定生长中期草鱼的蛋氨酸需要量。选用平均体重为(259.00±0.48)g的草鱼900尾,随机分为6个处理(每个处理5个重复,每个重复30尾),分别饲喂蛋氨酸水平为2.19、4.72、7.18、9.67、12.21和14.69 g/kg的试验饲料,试验期49 d。结果表明:与蛋氨酸水平为2.19 g/kg时相比,提高饲料中蛋氨酸水平显著地提高了生长中期草鱼的增重、摄食量、饲料效率、特定生长率和蛋白质效率(P<0.05)。当蛋氨酸水平达到7.18 g/kg时,增重和特定生长率达到最大值。蛋氨酸水平显著影响生长中期草鱼的肝胰脏和肠道重量、肝胰脏和肠道蛋白质含量以及肠道长度(P<0.05),对肝体指数没有显著影响(P>0.05)。当蛋氨酸水平≥4.72 g/kg时,肝胰脏和肠道重量以及肠道长度在各处理间差异不显著(P>0.05)。肝胰脏和肠道蛋白质含量分别在蛋氨酸水平为9.67和12.21 g/kg时达到最大值。当蛋氨酸水平为7.18 g/kg时,肝胰脏和肠道胰蛋白酶、糜蛋白酶和脂肪酶活性均达到最大值。当蛋氨酸水平为4.72 g/kg时,肠道淀粉酶活性达到最大值,且与其他处理间差异达到显著水平(P<0.05)。蛋氨酸水平显著影响各肠段Na+,K+-ATP酶、碱性磷酸酶、γ-谷氨酰转肽酶和肌酸激酶活性(P<0.05)。由此得出,饲料中适宜水平的蛋氨酸可以提高生长中期草鱼的生长性能和消化吸收能力。以特定生长率为标识,当饲料胱氨酸含量为1.61 g/kg时,生长中期草鱼(259～498 g)的蛋氨酸需要量为10.41 g/kg饲料或34.71 g/kg蛋白质。

This experiment was conducted to study the effects of dietary methionine level on growth performance,digestive and absorptive ability of grass carp(Ctenopharyngodon idell) during middle growth stage,and to determine the methionine requirement of grass carp during middle growth stage.A total of 900 grass carp with an average body weight of(259.00±0.48) g were randomly assigned to 6 treatments with 5 replicates per treatment and 30 fish per replicate.The fish were fed 6 experimental diets containing different levels(2.19,4.72,7.18,9.67,12.21 and 14.69 g/kg,respectively) of methionine for 49 d.The results showed as follows: compared with the 2.19 g/kg methionine,increasing dietary methionine level significantly improved the weight gain,feed intake,feed efficiency,specific growth rate and protein efficiency ratio(P<0.05).When methionine level arrived at 7.18 g/kg,the weight gain and specific growth rate had the highest values.Methionine level had significant effects on hepatopancreas and intestine weight,hepatopancreas and intestine protein content and intestine length(P<0.05),but had no significant effects on intestosomatic index(P>0.05).When methionine level is greater than or equal to 4.72 g/kg,no significant differences were found in hepatopancreas and intestine weight and intestine length among all treatments(P>0.05).The hepatopancreas protein content and intestine protein content had the highest values when methionine level reached 9.67 and 12.21 g/kg,respectively.The activities of trypsin,chymotrypsin and lipase in intestine and hepatopancreas got the highest values when methionine level was up to 7.18 g/kg.The highest value of amylase activity in intestine were found in 4.72 g/kg methionine treatment,and there was significant effects between 4.72 g/kg methionine treatment and other treatments(P<0.05).The activities of Na+,K+-ATPase,alkaline phosphatase,γ-glutamyl transpeptidase and creatine kinase in each intestinal segment were significantly affected by methionine level(P<0.05).It is concluded that the optimal levels of dietary methionine can improve the growth performance,digestive and absorptive ability of grass carp during middle growth stage.Based on specific growth rate,the dietary methionine requirement of middle growth stage grass carp(259 to 498 g) is estimated to be 10.41 g/kg(34.71 g/kg crude protein) in the presence of 1.61 g/kg cystine.