| Theanine is a non-protein amino acid unique component for tea plant,which can improve growth rate,enhance immunity,and intestinal flora for animal growth by adding it to animal feed.Larimichthys crocea(L.crocea)is one of the most important marine fish in China.In this study,juveniles of L.crocea were used as research objects.By adding different doses of theanine to the bait,the different amounts of juveniles were compared.The effects of growth,immunity and quality are expected to lay a theoretical foundation for the development of environmentally friendly feed additives for L.crocea.The main results of this study are as follows:1.HPLC method is suitable for theanine determination.The R2 of the standard curve obtained is 0.996.Under the conditions of material ratio 1:40(g/mL),ultrasonic 50 min,temperature 60? and power ultrasonic 50 w,theanine yield reached 1.77%.2.The added concentration of theanine in the feed was set at 0%,0.5%,1%,1.5%,2%.After 60 days of feeding,compared with the control group(0% added group),all the experimental groups could significantly improve the survival rate of L.crocea,especially in the 1% added group,the survival rate of L.crocea was the highest(P < 0.05).However,the effect of each experimental group on the weight increase of L.crocea was not significant(P > 0.05),and the specific growth rate of body mass,body length and total length did not show significant differences.3.Compared with the control group,the contents of immunoglobulin,superoxide dismutase,lysozyme and catalase in each addition group were significantly increased,indicating that the addition of theanine could effectively improve the antioxidant capacity of L.crocea.In particular,the activity of each enzyme was the highest in the 1% addition group.In addition,with the addition of theanine,the morphology of red blood cells,white blood cells and other blood cells are also affected,and the maturation rate is significantly accelerated.4.The results of quality analysis showed that theanine could increase the moisture content in the muscles of L.crocea and reduce the protein and fat content,but had no significant effect on ash content.In terms of amino acid content,the amino acid index EEAI was higher than the control group when theanine content was 1%,1.5% and 2%,and reached 66 when theanine content was 2%.In terms of fatty acid composition,theanine has little effect on the proportion of saturated fatty acid,monounsaturated fatty acid and polyunsaturated fatty acid.However,the content of polyunsaturated fatty acids was significantly increased,reaching 11.33% in the 2% added group,1.2 times that of the control group.The changes of quality components have a certain effect on maintaining the normal physiological function and improving immune capacity of croaker.Based on the above results,a certain dose of theanine can improve the growth survival rate of L.crocea,improve the enzyme activity of a variety of immune-related enzymes in the fish,and affect the content of protein and fat in the fish,suggesting that theanine can be used as a new feed additive in the production practice of L.crocea. |
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