| Brachymystax lenok was used as experimental subjects.0,0.2% and 1% golden algal β-glucan and yeast β-glucan were added into basical feed,respectively named as G1(control group),G2(0.2% golden algal polysaccharide),G3(1% golden algal polysaccharide),G4(0.2% yeast polysaccharide),G5(1% yeast polysaccharide).It amis to study the effects of different sources ofβ-glucan on the growth,serum biochemistry,intestinal health and disease resistance of Brachymystax lenok.The main results are as follows:1.Effects of β-glucan from different sources on growth and feed utilization of Brachymystax lenokAfter 8 weeks of feeding Brachymystax lenok with different β-glucan,the survival rate of all groups was higher than 96%,and the final body mass,weight gain rate,specific growth rate and feeding intake rate of each β-glucan addition group were significantly higher than the control group(p<0.05),but the feed coefficient and organ body ratio were significantly lower than those in the control group(p<0.05).The fullness of feeding intake rate in the G5 group was significantly lower than that in the control group(p<0.05),and there was no significant difference in liver-to-body ratio between the groups(p>0.05).2.Effects of β-glucan from different sources on body composition and serum biochemical of Brachymystax lenokThe addition of β-glucan from different sources in feed significantly reduced the crude fat content of fine-scale Brachymystax lenok(p<0.05),among which the two groups(G3 and G5)with1% addition were significantly lower than the two groups(G2 and G4)with 0.2% addition.The ash content of whole fish in G3 and G4 groups was significantly higher than that in G1,G2 and G5groups(p<0.05).The serum total cholesterol content of G2,G3,G4 and G5 groups was significantly lower than that in G1 group(p<0.05).The triglyceride content in G2 and G4 groups was lower than that in G1 group and higher than that in G3 and G5 groups,and the triglyceride content in G3 and G5 groups was significantly lower than that in G1 group(p<0.05).LDL cholesterol in the G2,G3,G4 and G5 groups was significantly lower than that in the G1 group(p<0.05).The bile acid content in the G3 group was significantly lower than that in the G1 group(p<0.05).3.Effects of β-glucan from different sources on intestine health in Brachymystax lenokThe addition of β-glucan from different sources significantly increased the expression(p<0.05)of intestinal complement(C3,C4)and tight junction protein(cldn-1,OCLN,ZO-1)of Brachymystax lenok with different sources,among which the two groups(G3 and G5)with 1%addition were significantly higher than those in the two groups(G2 and G4)(p<0.05)with 0.2% of the added amount,and the expression of C4 gene in G3 group was significantly higher than that in G5 group(p<0.05).The expression of ZO-1 gene in the G3 group was significantly higher than that in the G5 group(p<0.05).The addition of β-glucan from different sources in feed also significantly affected the expression of intestinal inflammatory factor genes in Brachymystax lenok,among which the expression of IL-1β,IL-8 and TNF-α pro-inflammatory factor genes decreased significantly,and the expression of IL-1β,IL-8 in G5 group and TNF-α gene in G3,G4 and G5 groups were significantly lower than those in other treatment groups(p<0.05).The intestinal villi length and muscular thickness of the β-glucan addition group were significantly higher than those in the control group(p<0.05),but there was no significant difference between the added groups.In the analysis of intestinal microbiota of Brachymystax lenok,the intestinal microbial diversity of the β-glucan addition group was significantly lower than that of the control group(p<0.05),the abundance of Exiguobacterium in G2 and G3 groups was significantly higher than that in G1 group(p<0.05),the abundance of Streptococcus and Lactococcus was significantly lower than that in G1group(p<0.05),and the abundance of Pediococcus in G2,G3 and G4 groups was significantly higher than that in G1(p<0.05).4.Effects of β-glucan from different sources on resistance to Aeromonas salmonicides in Brachymystax lenokThe survival rates of each group after 5 days of infection with Aeromonas salmonicida were32.5%,47.5%,57.5%,35.0% and 42.5%,respectively.Before infection,there was no significant difference in CAT activity between the β-glucan addition group and the control group(p>0.05).GPx activity was significantly higher than that of the control group(p<0.05),but there was no significant difference between the β-glucan addition group(p>0.05).The MDA content in theβ-glucan addition group was significantly lower than that in the control group(p<0.05),and the MDA content in the G3 and G5 groups was significantly lower than that in the G2 and G4 groups(p<0.05).The SOD activity in the G3 group was significantly higher than that in the G1 group(p<0.05).After infection,CAT activity in G2 group was significantly higher than that in G4 group(p<0.05).The activity of GPx decreased significantly compared with that before infection,and the G2,G4 and G5 groups were significantly lower than those in the G1 group(p<0.05),and the G4 and G5 groups were significantly lower than those in the G2 group(p<0.01).The content of MDA was significantly higher than that before the infection,and the G2 and G3 groups were significantly lower than those in the G1 group(p<0.05).The activity of SOD decreased significantly compared with that before infection,and the G2 group was significantly higher than that in the G4 group(p<0.05).In summary,the addition of β-glucan to feed can significantly improve the immunity of Brachymystax lenok,improve the body’s lipid metabolism and intestinal health,and can improve the anti-Aeromonas salmonicida ability of Brachymystax lenok.Golden algal β-glucan was superior to yeast β-glucan in improving the non-specific immunity of Brachymystax lenok and the ability to resist Aeromonas salmonicida. |
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