| Chlorella Growth factors(Chlorella Growth Factor,CGF)is a unique active substance in Chlorella cells.It not only can promote the cell growth,but also has a series of physiological functions,including the enhancement of immunity,the improvement of the antioxidant activity and so on.The application prospect is widespread.At this moment,the research of the physiological and ecological influence and its mechanism on the aquatic invertebrates of CGF is still blank.In this paper,the marina shrimp(Litopenaeus vannamei)young shrimp is set as the test object,five treatment groups(0.5 %,1 %,5 %,10 %,15 %)are built according to the addition of the CGF proportion respectively,with no added feed as the control group(0 %).45 d cultivation experiment is conducted,and the prawn growth,digestive,nutrition and immune performance etc.are tested at the end.On the other hand,another 1 % group and the control group are selected for non-ionic ammonia stress test(0.5mg/L)at the end of the cultivation,and the physiological and ecological response rules of the two groups to non-ionic ammonia stress are compared.The main research contents and results are as follows:(1)Effects of CGF on growth,basal body composition and digestive enzymes of Litopenaeus vannameiThe addition of CGF in the feed can significantly improve the survival rate,weight gain rate and specific growth rate,and reduce the feed coefficient of Litopenaeus vannamei.With the increase of the adding proportion of CGF,prawn survival rate,weight gain rate and specific growth rate tend to increase first and then decrease,all indexes have reached the highest in the 1 % group.The tendency of feed coefficient is in opposite,the lowest locates in the 1 % group.Dietary CGF supplementation has influences on basal body composition of Litopenaeus vannamei.The crude protein content has been increased,whilst the moisture,ether extract and ash content have been decreased.Among all experimental groups,the 1 %group has the lowest moisture,ether extract and ash content,and the highest crude protein content.Different concentrations of CGF have different effects on the digestive enzyme activities of Litopenaeus vanname.The lipase in the 0.5 % group has been significantly increased compared with the control group(P<0.05),the 1 % group has significant effects on amylase,lipase and protease(P<0.05).With the increase of dietary supplemental concentration,lipase and protease in the 5 % group has reached the highest values.(2)Effects of CGF on nutrients and flavoring substances of Litopenaeus vannameiAfter the cultivation experiment,the types and contents of amino acids,fatty acids and related indexes of muscle quality(inosinic acid,hypoxanthine,monophosphate,creatine kinase)are measured in the muscle tissue of the shrimps.The results showed that dietary supplementation of 10～15 % CGF can significantly increase the contents of total fatty acids,saturated fatty acids,monounsaturated fatty acids and polyunsaturated fatty acids.Dietary CGF supplementation could increase the proportion of polyunsaturated fatty acids but decrease the proportion of saturated fatty acids and monounsaturated fatty acids.The proportion of saturated fatty acids in 1 % group is the lowest.All treatment groups(except10 % treatment group)could significantly increase the total amino acid content and essential amino acid content(P<0.05).The contents of essential amino acids and flavor amino acids in1 % supplemental group are significantly higher than those in the control group and other experimental groups(P<0.05).The essential fatty acid contents of arachidonic acid,linoleic acid,α-linolenic acid,EPA and DHA have shown an increasing trend,and the essential fatty acid indexes of the 1 % group are significantly different from those of the control group(P<0.05).The supplementation of high proportion of CGF can significantly promote the accumulation of fatty acids,while the appropriate proportion(1～5 %)of CGF can significantly reduce the proportion of saturated fatty acids,and increase the contents of polyunsaturated fatty acids and essential fatty acids.The muscle quality indexes of Litopenaeus vannamei have been changed when different concentrations of CGF are added into the diets.The monophosphate and creatine kinases in the high-concentration treatment group(10 ～15 %)differ evidently from those in the control group(P<0.05).Inosinic acid content gradually increase with the increase of supplemental level,and there are significant differences between all treatment groups and the control group,except the 0.5% group(P<0.05).Compared with the control group,hypoxanthine has been increased in all treatment groups except the 1 % group.Overall,the 1 % group is more advantageous,with a significant difference in inosinic acid content compared to the control group(P<0.05),and the hypoxanthine content is the lowest.(3)Effects of CGF on immunity and response to non-ionic ammonia stress in Litopenaeus vannameiAfter the cultivation experiment,the hepatopancreas of shrimps are collected to measure the immune enzyme activities: acid phosphatase(ACP),alkaline phosphatase(AKP),superoxide enzyme(SOD),nitric oxide synthase(NOS),glutathione peroxidase(GSH-Px),malondialdehyde(MDA).The results show that the diet supplemented with 1 % CGF is most beneficial to the metabolism of shrimps(P<0.05),enhancing its immunity and improving the activity of ACP and GSH-Px.The activities of AKP,SOD and GSH-Px in hepatopancreas of Litopenaeus vannamei are significantly affected by the 5 % CGF addition(P<0.05).The content of MDA is decreased while the NOS activity is increased at 0.5% concentration(P<0.05).On the other side.the changes of hepatopancreas immune indexes(ACP,AKP,NOS,SOD,MDA,GSH-Px)and muscle respiratory metabolic enzymes(HK,PK,LDS,SDH)in the 1% and the control groups are measured after non-ionic ammonia stress test.The results showed that the activities of ACP,AKP,NOS and SOD in hepatopancreas of Litopenaeus vannamei are significantly increased by 1 % CGF supplementation(P<0.05),and the content of MDA in hepatopancreas is reduced.After non-ionic ammonia stress test,the activities of ACP,AKP,SOD,NOS and GSH-Px in hepatopancreas of the 1% group are firstly decreased and then increased versus time,while MDA shows an opposite trend.With the extension of stress time,ACP,NOS and SOD in the control group first decrease and then increase,GSH-Px continues to decrease,and MDA content continuously accumulate.MDA content in the control group is significantly higher than that in the treatment groups(P<0.5).The overall activities of PK,LDS and SDH in Litopenaeus vannamei muscle at 24 h are higher than those in the control group,and HK in the experimental groups at 3h are also significantly higher than those in the initial stage of the experiment,indicating that 1 % CGF supplementation in the diet can reduce the damage of Litopenaeus vannamei under non-ionic ammonia stress and improve its immune regulation ability.To sum up,appropriate proportion addition of CGF in the feed can obviously improve the growth performance,improve the accumulation of nutrients,especially reduce the proportion of the unsaturated fatty acid,and increase the fatty acid and the amino acid content,promote the accumulation of muscle flavor substances,which is in favor of the body’s immune function,and beneficial to the body’s resistance to stress of non-ionic ammonia.The suitable adding proportion is 1 %. |
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