大型溞的营养成分分析及其作为渔用饲料原料的潜在利用价值

为了评估大型溞在渔用饲料中的的营养价值,测定了不同季节人工培养的大型溞和夏季污水中大型溞风干样的营养成分与重金属含量。结果显示,各季节人工培养的大型溞水分含量存在显著的季节差异,冬季最高为5.14%,夏季最低为2.51%;夏季污水中大型溞水分含量(9.12%),显著高于人工培养的大型溞。人工培养的大型溞粗蛋白含量为30.93%~50.21%,在不同的季节也存在显著性差异,冬季人工培养、夏季污水中大型溞粗蛋白含量显著高于其他组。大型溞的15种氨基酸含量在各季节中差异显著,冬季最高(36.65%),夏季最低(24.74%);夏季污水中氨基酸含量为41.79%,9种必需氨基酸占22.15%,赖氨酸含量达到3.4%,蛋氨酸的含量为1.14%,苏氨酸含量为2.45%。大型溞粗脂肪含量随季节变化差异显著,冬季最高(18.88%),秋季最低(4.19%),夏季污水与冬季人工培养的大型溞无显著性差异。秋季人工培养的大型溞与夏季污水大型溞必需脂肪酸含量最高,为17%左右,所有大型溞中均没有检测到花生四烯酸和亚麻酸。重金属铬、铜和锌、铅最高含量分别出现在夏季污水、秋季、春季、夏季人工培养大型溞;夏季污水和冬季人工培养大型溞中未检测到铅元素,所有大型溞中均没有检测到镉元素。除铬外,铜、铅、砷和锌的最低含量均出现在夏季污水大型溞中。研究表明,大型溞蛋白质、脂肪营养丰富,而夏季污水大型溞必需氨基酸和必需脂肪酸营养价值普遍高于人工培养的大型溞,且重金属潜在毒性较低,作为渔用饲料蛋白源进行资源化利用的可行性更高。

Nutrient analysis and potential utilization value of Daphnia magna used as aqua-feed raw material

A trial was conducted to determine nutrient composition and heavy metal content of dried Daphnia magna from artificial-cultivation pond in spring, summer, autumn, winter and eutrophic lake sewage in summer, aiming to assess potential utilization value in aqua-feed. The results showed that there was significant seasonal difference in the moisture of artificial cultivated D.magna, and the highest was 5.14% in winter, and the lowest was 2.51% in summer. The moisture content (9.12%) of D.magna in summer sewage was significantly higher than that of artificial cultivation. The content of protein of artificially cultivated D.magna was 30.93% - 50.21% with significant differences in different seasons, and in winter and summer sewage was significantly higher than that of other groups. The total content of 15 amino acids determined markedly differed among groups, with the highest (36.65%) in winter and the lowest in summer (24.74%).In summer sewage, the amino acid content was 41.79%, and 9 essential amino acids accounted for 22.15%, lysine content reached 3.4%, methionine 1.14%, and threonine 2.45%. The fat content was also significantly different with seasonal variation, the highest fat content was observed in winter (18.88%), while the lowest in autumn (4.19%), and no significant difference on the fat content was found in winter and summer sewage. The essential fatty acids were the highest in autumn and the summer sewage (17%),and the arachidonic acid and linolenic acid were not detected in all samples. The highest levels of heavy metal chromium, copper, zinc and lead appeared in summer sewage and artificial-cultivation pond in autumn, spring and summer, respectively, and no lead was detected in summer sewage and winter, no cadmium in all groups. Except for chromium, the lowest concentrations of copper, lead, arsenic and zinc were found in the summer sewage. All the results indicated that the D.magna was rich in protein and fat with lower potential toxicity of heavy metals, and both the essential amino acid and essential fatty acid nutrient values in summer sewage were generally higher than those of artificial cultivation, so it is more feasible to use D.magna in summer sewage as the feed protein source.