Effects Of Glutathione On Grouth Performance And Intestinal Health In Oncorhynchus Mykiss

This experiment was conducted to investigate the effects of glutathione on growth performance and intestinal health of juvenile Oncorhynchus mykiss.A total of 450 Oncorhynchus mykiss with an average body weight of?4.12±0.04?g were randomly divided in 5 groups with 3replicates per group and 30 fish per replicate.Triplicate groups of Oncorhynchus mykiss were fed one of four diets which were formulated to contain glutathione 0 mg·kg^-1?control group,R0?,100mg·kg^-1?R100?,200mg·kg^-1?R200?,400mg·kg^-1?R400?,800mg·kg^-1?R800?for 8-week.The results of the study are presented as follows:1.The effects of dietary glutathione supplementation on growth performance,feed utilization and nutrient composition of Oncorhynchus mykiss.The survival rate?SR?,weight gain rate?WGR?,specific growth rate?SGR?and average feed intake?FI?increased and the feed coefficient?FCR?decreased when the dietary glutathione supplementation<400 mg·kg^-1 for Oncorhynchus mykiss.With the further increase of the glutathione supplementation,the SR,WGR,SGR and FI showed the downward trends.Dietary glutathione supplementation had no obvious influence on the moisture and ash of Oncorhynchus mykiss?P>0.05?.The whole body protein and fat contents of R400 and R800 groups were significantly increased compared with the control group?R0??P<0.05?.According to the relationship between the weight gain rate against of dietary glutathione supplementation,the suitable addition amount of glutathione for the Oncorhynchus mykiss was 400 mg·kg^-11 by the broken-line model analysis.2.The effects of dietary glutathione supplementation on intestinal tissue changes of Oncorhynchus mykiss.Intestinal morphometry demonstrated that the thickness of the muscular layer,the height of the intestinal villi and the number of goblet cells increased gradually with the increase of dietary glutathione supplementation,but no significant effect was observed in the height of the fold?P>0.05?.Intestinal histology found that the intestine villi of each group were intact and the epithelial cells were arranged neatly and tightly in all groups,and some muscle layers were damaged in R800 group.3.The effect of dietary glutathione supplementation on the nutrient transporter and non-specific immune gene of intestinal for Oncorhynchus mykiss.The oligopeptide transporter?PepT1?,amino acid transporter?SLC1A5?and sodium phosphate transporter?NaPi-IIb?mRNA levels of Oncorhynchus mykiss were increased,but the mRNA levels of interleukin-1??IL-1??,interleukin?IL-2?,interleukin-8?IL-8?and the tumor necrosis factor-??TNF-??decreased with increased dietary glutathione supplementation levels?P<0.05?.4.The effect of dietary glutathione supplementation on the microbial diversity of Oncorhynchus mykiss.The results showed that most of the microorganisms in the intestinal of the Oncorhynchus mykiss were bacteria.Chao1 index,Ace index and Shannon index were increased with increased dietary glutathione supplementation levels.When the glutathione in the feed was 200 mg·kg^-1,the abundance of the intestinal flora of the Oncorhynchus mykiss reached a significant level?P<0.05?.The main dominant bacteria were Proteobacteria,Firmicutes and Bacteroidetes,of which Firmicutes/Bacteroidetes have an increased trend.In conclusion,adding a certain amount of glutathione to the feed can significantly promote the growth performance,improve the survival rate,reduce the feed coefficient,and improve the protein and fat content of the Oncorhynchus mykiss.The peristalsis ability of the intestinal and the absorption area and efficiency of nutrients?mainly including small peptides,amino acids and phosphorus?can be improved by promoting the intestinal tissue structure?increasing muscle layer thickness,microintestinal villi height?and the gene expression of nutrient transporters.In addition,it can also inhibit the expression of pro-inflammatory cytokines,increase the abundance and uniformity of intestinal microbes,promote the barrier function of intestinal mucosa,and also contribute to the stability of intestinal health.