饲料异亮氨酸水平对卵形鲳鲹消化酶活性和免疫指标的影响

实验旨在研究饲料异亮氨酸(Ile)水平对卵形鲳鲹(Trachinotus ovatus)消化酶活性和免疫指标的影响。以鱼粉、豆粕、花生粕和L-晶体氨基酸为蛋白源,配制含粗蛋白430 g·kg~(-1)的6种等氮饲料,各组分别含有13.2 g·kg~(-1)、15.7 g·kg~(-1)、18.2 g·kg~(-1)、20.7 g·kg~(-1)、23.2 g·kg~(-1)和25.7g·kg~(-1)(以干物质计)异亮氨酸。每组3个重复,每个重复随机放置20尾鱼初始体质量(6.36±0.03)g],实验时长8周。结果显示,各实验组的肠淀粉酶和胃蛋白酶活性、血清总抗氧化能力(T-AOC)、溶菌酶(LZM)活性、免疫球蛋白M和补体(C3和C4)浓度均随着饲料Ile水平的升高而先上升后下降,这5个指标的较高值出现在18.2 g·kg~(-1)和20.7 g·kg~(-1)组,而较低值则出现在13.2 g·kg~(-1)和25.7 g·kg~(-1)组,上述4组与其他2组差异显著。血清尿素氮和丙二醛(MDA)浓度的变化趋势则与上述7个指标相反,较低值出现在18.2 g·kg~(-1)和20.7 g·kg~(-1)组,且显著低于其他4组。血清超氧化物歧化酶(SOD)活性则随着饲料Ile水平的增加而显著升高,18.2~25.7 g·kg~(-1)这4组SOD活性没有显著性差异。综上所述,饲料Ile水平为18.2~20.7 g·kg~(-1)时,卵形鲳鲹具有较好的消化性能和免疫机能。

Effects of dietary isoleucine levels on activities of digestive enzymes and immune index of Trachinotus ovatus

We investigated the effects of dietary isoleucine on the digestive enzymes and immune index of juvenile golden pompano,Trachinotus ovatus.Six diets with different concentrations of L-isoleucine(13.2 g·kg-1,15.7 g·kg-1,18.2 g·kg-1,20.7 g·kg-1,23.2 g·kg-1 and 25.7 g·kg-1 dry diet)were formulated to contain 430 g·kg-1 crude protein with fish meal,soybean meal,peanut meal and pre-coated crystalline amino acids.Each diet was randomly assigned to triplicate treatments of 20 fish initial body weight was(6.36±0.03)g] for eight weeks.The intestinal amylase and pepsase activities,serum T-AOC and LZM activities,IgM concentrations increased with increasing isoleucine concentration up to 18.2 g·kg-1,whereas decreased in the groups exceeding 20.7 g·kg-1isoleucine significantly.Those parameters of the fish fed with diets of 15.7 g·kg-1and 23.2 g·kg-1isoleucine were significantly higher than those fed with diets of 13.2 g·kg-1and 25.7 g·kg-1isoleucine,while significantly lower than groups containing 18.2 g·kg-1and 20.7 g·kg-1isoleucine.There is an opposite change trend in serum urea and MDA concentration,i.e.,significantly lower in 18.2 g·kg-1and 20.7 g·kg-1isoleucine groups than those in the other groups.The SOD activity rate increased with increasing isoleucine concentration up to 18.2 g·kg-1,and there was no significant difference when the dietary isoleucine exceeded 18.2 g·kg-1.So diet with 18.2～20.7 g·kg-1isoleucine can improve the digestive performance and immune function of T.ovatus.