Effects Of Butyrate Glycerides Supplementation In High Soybean Meal-based Diet Of Juvenile Black Sea Bream(Acanthopagrus Schlegelii)

Multiple progresses have been made to evaluate soybean meals(SBM)as a potential replacement of fish meal(FM)in aquafeed production,but high or total replacement of FM by SBM has not been achieved perhaps because of the limiting amino acids and the presence of anti-nutritional factors in SBM.To overcome these limitations feed additive was suggested to be supplemented in diet.Butyrate glycerides,a butyrate derivate,have shown to play an important role in maintaining the gastrointestinal health as well as improving animal growth performance.Butyrate glycerides are involved in intestinal barrier defense,inflammatory and oxidative status,cell growth and differentiation,and intestinal immunoregulation.Therefore,addition of butyrate glycerides in the diet has gained particular interest in animal production.Among farm fish cultured in China,black sea bream is a valuable commercial fish highly appreciate for its meat.This research study therefore focusses on the supplementation of butyrate glycerides in high SBM based diet of black sea bream.To achieve this objective four main experiments has been conducted,and the main findings obtained are summarized as follows:1.This study was conducted to investigate the effects of addition different level of tributyrin in high SBM-based diet.Seven experimental diets were designed:PC(456 g kg-1 FM,120 g kg-1SBM),NC(209 g kg-1 FM,450 g kg-1 SBM)and TB diets made of NC diet supplied with gradual levels at 0.5,1,2,4 and 8 g TB kg-1.Eventually,fish fed PC diet had higher weight gain and specific growth rate than the other dietary treatments.Fish fed the NC diet had the lowest growth and addition of TB in the diet increased black sea bream growth up to TB 0.2 diet while greater supplementation tend to decrease the growth rate.The feed utilization did not vary among the dietary treatments and fish fed the PC diet had higher phosphorus discharge compared to the dietary high SBM based.Dietary TB showed to improve the protease activity and enhance antioxidant capacity.Furthermore,fish fed the NC diet developed multiple sign of intestine inflammation,as confirmed by the histological examination and the expression of target genes.The addition of TB in the diet showed to improve intestinal morphology structure;up regulated the expression of GPR41,CLDNI and decrease the expression of IL-1,TNF1,CAS3 level.2.This experiment aimed to investigate the effects of graded level of mixture butyrate glycerides(MB)supplementation in high soybean meal diet of juvenile black sea bream.The MB(56%content)was composed by mono(340 g kg-1),di(190 g kg-1)and tri(30 g kg-1)-butyrin.Six experimental diets were designed containing 199 g kg-1 FM and 450 g kg-1 SBM,supplied with gradual levels at 0,2,4,6,8 and 16 g MB kg-1.The results showed that weight gain and specific growth rate of fish increased with increasing dietary MB supplementation up to fish fed MB6 diet while further increment of MB level led to a significant(P<0.05)decrease of growth rate.Dietary MB supplementation increased the activity of intestinal protease,but had no significant(P>0.05)effect on intestinal lipase and amylase activities.Fish fed the basal diet exhibited a villus shortening with a decrease in the number of goblet cells and a reduction of absorptive and digestive epithelial surface,while fish fed the MB4,MB6,MB8 and MB 16 diets showed a well-integrated gut,with large absorptive surface and digestive epithelial surface.Supplementation of MB in diet also improved antioxidant capacity of black sea bream by increasing superoxide dismutase and glutathione peroxidase activities while decreasing malondialdehyde content.3.A comparison between four types of diets:PC(high FM-low SBM),MB,TB and microencapsulated sodium butyrate(MSB)was evaluated.The optimum level of MB,TB and MSB was added in high SBM based diets which are 4.98,2.24 and 2.40 g kg-1 respectively.The results showed that juvenile black sea bream had similar growth performance among all dietary treatment.The TEM observation revealed close appearance in gut ultrastructure with long-dense brush border and tight junction in all dietary treatments;however,dietary TB and MSB demonstrated high epithelial cell vacuolization.4.The gut microbial composition of black sea bream fed the PC,MB,TB and MSB were investigated in this experiment.Our results showed no significant difference in OTUs and the alpha diversity of gut microbiota of black sea bream fed all dietary treatment Moreover,the Proteobacteria,Cyanobacteria,Actinobacteria,Firmicutes and Acidobacteria were the most dominant phylum found in black sea bream gut,where the MB group had the lowest Proteobacteria abundance and the highest Cyanobacteria abundance compared to the other dietary treatment group.In summary,the inclusion of butyrate glycerides in high SBM diets can improve growth performance,maintain healthy gut morphology and enhance antioxidative capacity of black sea bream.Moreover,the addition of the optimum level of butyrate glyceride in high SBM based diet lead to a similar growth performance of black sea bream fed with high FM diet.