不同饵料对美洲西鲱仔鱼生长、相关酶活力及体脂肪酸的影响

Effects of different diets on growth performance, enzyme activity, and body fatty acid composition in larval American shad(Alosa sapidissima)

以美洲西鲱(Alosa sapidissima)仔鱼(孵化后10 d)为实验对象,在室内进行为期30 d的摄食生长试验,分别投喂不同的饵料[单独投喂卤虫(Artemia)、单独投喂微颗粒饲料、卤虫与微颗粒饲料混合投喂],分析不同饵料的投喂对存活、生长、消化酶活性、非特异性免疫相关酶活性以及体脂肪酸组成的影响。结果表明:(1)混合投喂组的存活与生长表现都要显著优于卤虫组和微颗粒饲料组(P<0.05),微颗粒饲料组与卤虫组相比差异不大,而试验后期(20~30 d)微颗粒饲料组的存活与生长表现要优于卤虫组;(2)消化酶的结果显示,胃蛋白酶和淀粉酶活力在各组中无显著性差异(P>0.05),胰蛋白酶、糜蛋白酶和脂肪酶在卤虫组中活力最低,显著低于其他两组(P<0.05),其中糜蛋白酶和脂肪酶活性在微颗粒饲料组中要显著高于混合投喂组(P<0.05);(3)碱性磷酸酶和超氧化物岐化酶活力在各组中无显著性差异(P>0.05),过氧化氢酶和溶菌酶活力在微颗粒饲料组中最高,卤虫组中最低,两者之间差异显著(P<0.05);(4)鱼体脂肪酸受饵料脂肪酸组成影响较大,微颗粒饲料中n-3HUFA和DHA含量较高,其投喂后在鱼体中的含量也高。综上所述,不同饵料投喂对美洲西鲱仔稚鱼存活、生长、消化酶活性、非特异性免疫相关酶活性以及体脂肪酸影响显著,在试验20 d之前使用卤虫与微颗粒饲料混合投喂,20 d后完全转食微颗粒饲料,可以降低成本,同时提高生产效率。

The American shad, Alosa sapidissima, is an economically and ecologically valuable anadromous herring native to the Atlantic coast of North America, which was introduced into China as an alternative species to the Chinese shad Tenualosa reevesii （because of the latter＇s near extinction）, and is considered as an emerging aquaculture species in China. However, the high mortality rate in the early stage of development, particularly after ingestion of exogenous food, has seriously restricted the development of the industry. Therefore, food selection during seed rearing has important significance. In the present study, the effect of different diets, on growth performance, survival, digestive enzyme activity, immune response, and body fatty acid composition in larval American shad were assessed. Larvae of American shad, 10 d after hatching, were reared with different diets （Artemia, micro diet, and mixed feeding Artemia and micro diet）, in triplicate, for 30 d cultivation. The survival and growth performance （survival rate, total length, body weight, and specific growth rate） in the mixed feeding group were significantly better than those in the other two groups during the studied period （P〈0.05）. This may be attributable to the difficulty in digesting micro diets during the early experiment stage and the deficiency of essential fatty acids in Artemia, particularly the deficiency of n-3 highly unsaturated fatty acids （n-3HUFA） and docosahexaenoic acid （DHA）. There were no obvious differences between the micro diet group and Artemia group; however, the survival and growth performance of the micro diet group during the 20 d-30 d period were better than those in the Artemia group （P〈0.05）. This may be because larval fish can digest and absorb micro diets efficiently during this period; moreover, micro diets have a better nutrient content. There were no Significant differences in the pepsin and amylase activities among all groups, whereas the activities of trypsin, chymotrypsin, and lipase in the Artemia group were significantly lower than those in the other two groups （P〈0.05）. Furthermore, chymotrypsin and lipase activities in the micro diet group were significantly higher than those in the mixed feeding group （P〈0.05）. This indicates that fish larvae could digest micro diets efficiently at the end of experiment, and the addition of micro diets can improve digestive enzyme activities and digestion ability to a certain extent. There was no significant difference in the alkaline phosphatase and superoxide dismutase activities among all groups. The highest activities of catalase （CAT） and lysozyme （LZM） were recorded in the micro diet group, and the activities in this group were significantly higher than those in the Artemia group （P〈0.05）. There was a certain correlation between the survival performance during the 20-30 d period and the activities of CAT and LZM. The mortality in the micro diet group and mixed feeding group remained stable, whereas that in the Artemia group continued to decline during this period. This indicates that the addition of micro diets may enhance the non-specific immune response of larval fish. The fatty acid composition of fish larvae was affected considerably by the fatty acid composition of diets. Due to the higher content of essential fatty acids in micro diets, the contents of n-3 HUFA and DHA in the mixed feeding group and micro diet group were significantly higher than those in the Artemia group （P〈0.05）. The experimental results indicate that different diets have an obvious influence on the growth performance, survival, digestive enzyme activity, immune response, and body fatty acid composition of larval American shad. This preliminary analysis showed that mixed feeding with Artemia and micro diets before 20 d and full conversion to feeding with micro diets after 20 d can reduce costs and improve production efficiency.