Study On The Effects Of Fermented Plant Protein Sources On The Growth And Health Of Pacific White Shrimp,Litopenaeus Vannamei

In this paper,we studied the effects of fermented vegetable protein source replacing soybean meal on growth performance,antioxidant capacity,immune regulation and intestinal microflora of Litopenaeus vannamei.On this basis,the feasibility of organic acids and enzymes as functional additives in new protein-derived feeds was preliminarily explored.The main research content and findings of this thesis are divided into three aspects as follows.1.Effects of substituting soybean meal with fermented cottonseed meal on growth,Physiology,biochemistry and intestinal flora of L.vannameiThe experiment was divided into 6 groups: normal fish meal group Con(positive control),low fish meal group 25%,50%,75% and 100% soybean meal were replaced by fermented cotton meal on the basis of negative control FCSM0 group(soybean meal replaced 40% fish meal in Con),which were denoted as FCSM25,FCSM50,FCSM75 and FCSM100.The culture experiment lasted for 8 weeks.The results showed that the FCSM0 group had the lowest specific growth rate,survival rate and weight gain rate among the 6groups,and notably lower than the FCSM75 group(P < 0.05).The malondialdehyde content of hepatopancreas in FCSM25,FCSM75 and FCSM100 groups was notably lower than the Con group(P < 0.05).The activity of superoxide dismutase increased with the amount of substitution.The activities of serum alkaline phosphatase and acid phosphatase in all groups were notably lower than those in Con group(P < 0.01).The activities of hepatopancreas digestive enzymes(trypsin and amylase)in fermented cottonseed meal supplemental group were notably higher than the FCSM0 and Con group(P < 0.05).The results of intestinal bacteria sequencing showed that fermented cottonseed meal reduced the relative abundance of pathogenic bacteria(Vibrio,Photobacterium)and increased the diversity of intestinal bacteria.According to the KEGG function prediction results,the "metabolism","synthesis" and "transport" functional pathways were significantly affected after the addition of fermented cottonseed meal.In this study,replacing 75% soybean meal with fermented cottonseed meal in low fish meal diet can inhibit the growth of pathogenic bacteria,and improve the growth performance,antioxidant and immune capacity,and the intestinal microbial structure of L.vannamei.2.Effects of replacing soybean meal with fermented rapeseed meal on growth,physiology,biochemistry and intestinal health of L.vannameiL.vannamei with an initial weight of 1.04 ± 0.04 g was selected for an 8 weeks culture experiment.With normal fish meal group(FM)as positive control,the diets of low fish meal group were supplemented with negative control SM group(soybean meal replaced40% fish meal in FM group),and 25%,50%,75% and 100% soybean meal were replaced with fermented rapeseed meal,respectively,which were denoted as FRM25,FRM50,FRM75 and FRM100.We got a conclusion that the specific growth gain rate and weight rate were negatively correlated with the supplemental level of fermented rapeseed meal.The content of malondialdehyde in hepatopancreas in FM group was significantly higher than that in FRM25,FRM50 and FRM100 groups(P < 0.05).The activity of superoxide dismutase increased with the amount of substitution.There were no significant differences in serum phenol oxidase activity and lysozyme activity between FRM50 group and FM group(P > 0.05).Transcriptome results showed that high levels of fermented rapeseed meal in the diet significantly affected the expression of genes related to lipid metabolic pathways and led to downregulation of transcripts related to oxidoreductase activity.Increased levels of fermented rapeseed meal can also cause intestinal mucosa to separate from muscular layer.The intestinal flora sequencing results showed that the relative abundance of Bacteroidetes in FRM100 group was lower than that in SM group,and the relative abundance of Proteobacteria was higher than that in other groups.This study shows that fermented rapeseed meal can replace 25% of soybean meal in the diet without affecting the growth and health of L.vannamei.Beyond this replacement level,intestinal flora of penaeus prawn will be disturbed,lipid metabolism will be affected,and growth performance of penaeus prawn will be reduced.3.Effects of adding enzyme preparation and organic acid salt to fermented rapeseed meal feed on growth and health of L.vannameiThe experiment was divided into the following 7 groups: PC(high soya meal),NC(rapeseed meal replacing 30% soya meal in the SM group),TP(NC + protease),TB(NC +sodium butyrate),TB + P(NC + sodium butyrate + protease),TC(NC + sodium citrate)and TC + P(NC + sodium citrate + protease)groups.The PC group was used as a positive control and the NC group as a negative control.The initial weight of the prawns was 0.128± 0.01 g and the experimental period was 8 weeks.The results showed that except TC and TC+P,the weight gain rate and specific growth rate of the other groups were significantly lower than those of the PC group(P < 0.05).There were no significant differences in muscle hardness and masticability between TC group and PC group(P > 0.05).Plasma MDA content in TC+P group was significantly lower than that in PC group(P < 0.05).Blood cell count and hemocyanin content were significantly higher in all groups except the TB group compared to the negative control group(P < 0.05).The bacterolytic activity of TB group was higher than that of other 5 groups,and there was no significant difference between TB group and positive control group(P > 0.05).Intestinal flora sequencing results showed that compared with the negative control group,the relative abundance of verrucobacteria in TC,TP and TC+P groups was increased,and the effect of protease addition group was the most obvious.This study shows that the addition of organic acids and enzymes to fermented rapeseed meal can improve the growth performance and immunity of shrimps caused by the replacement of soybean meal by fermented rapeseed meal,with sodium citrate being the most effective in combination with protease.According to the above research,the utilization efficiency of different fermentable plant proteins is quite different.The fermented cottonseed meal can replace 75% soybean meal in the low fish meal diet,improve the intestinal flora structure of prawn and enhance its immune capacity.The replacement amount of fermented rapeseed meal was only 25%.High content of fermented rapeseed meal in diets can reduce the growth performance of penaeus prawn by affecting the structure of intestinal flora and gene expression of "oxidoreductase activity" and lipid metabolism related pathways in hepatopancreas.Although the addition of organic salt and enzyme preparation can alleviate the adverse effects of fermented rapeseed meal on L.vannamei to a certain extent,it has little effect.