Dietary supplementation of Streptococcus faecalis benefits the feed utilization, antioxidant capability, innate immunity, and disease resistance of blunt snout bream (Megalobrama amblycephala)

• Published in: Fish physiology and biochemistry Vol. 45; no. 2; pp. 643 - 656
• Main Authors: Zhong, Xiao-Qun, Liu, Ming-Yang, Xu, Chao, Liu, Wen-Bin, Abasubong, Kenneth-Prudence, Li, Xiang-Fei
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.04.2019; Springer Nature B.V
• Subjects: Animal Anatomy; Animal Biochemistry; Animal Physiology; Antioxidants; Biomedical and Life Sciences; Bream; Control; Dietary supplements; Disease resistance; Diseases; Feed conversion; Feeding experiments; Feeds; Fish; Freshwater & Marine Ecology; Histology; Immunity; Immunity (Disease); Immunoglobulin M; Innate immunity; Intestine; Life Sciences; Liver; Megalobrama amblycephala; Microvillus; Morphology; Mortality; Streptococcus faecalis; Tissue; Zoology; Blunt snout bream; Disease resistance; Innate immunity; Growth; Streptococcus faecalis
• ISSN: 0920-1742; 1573-5168
• DOI: 10.1007/s10695-018-0595-9

This study aimed to investigate the effects of Streptococcus faecalis on the growth performance, intestinal histology, antioxidant capability, innate immunity, and disease resistance of blunt snout bream Megalobrama amblycephala . Fish were fed five experimental diets containing 0 (SF0, control), 1 × 10 5 (SF1), 1 × 10 6 (SF2), 1 × 10 7 (SF3), and 1 × 10 8  cfu/g (SF4) of Streptococcus faecalis , respectively, for 10 weeks. After the feeding trial, fish were challenged by Aeromonas hydrophila with the cumulative mortality recorded during a period of 96 h. The results showed that WG and FI of fish both showed no significant difference ( P  > 0.05) among all the treatments. However, the FCR was significantly ( P  < 0.05) affected by Streptococcus faecalis levels with the lowest value observed in the SF2 group, whereas the opposite was true for intestinal microvillus length ( P  < 0.05). Dietary supplementation of 1 × 10 6  cfu/g Streptococcus faecalis significantly ( P  < 0.05) increased the hepatic activities of SOD, CAT, and GPx; plasma activities of LZM, MPO, ACP, and AKP; and the levels of C3, C4, and IgM of fish, compared with the control group. Similar results were also observed in the tissue expressions of Leap-I , Leap-II , muc2 , and muc5b ( P  < 0.05), whereas the opposite was true for liver MDA contents and plasma NO levels ( P  < 0.05). At 96 h after challenge, the cumulative mortality of the control was significantly ( P  < 0.05) higher than that of the SF2 group, but it showed no statistical difference ( P  > 0.05) with that of the other treatments. These results indicated that dietary supplementation of 1 × 10 6  cfu/g Streptococcus faecalis could not only improve the feed utilization of blunt snout bream but also enhance its antioxidant capability, innate immunity, and disease resistance.