The effects of host-associated Enterococcus faecium CGMCC1.2136 on serum immune parameters, digestive enzymes activity and growth performance of the Caspian roach (Rutilus rutilus caspicus) fingerlings

The effect of different dietary supplementation levels of host-associated Enterococcus faecium strain CGMCC1.2136 on the Caspian roach fingerlings was investigated. Three hundred and sixty fish with an average body weight of 12 g were randomly distributed into four treatments receiving different dietary inclusion levels (0 [control], 10(6), 10(7) and 10(8) CFU g(-1) feed) of E. faecium CGMCC1.2136. After an eight-week feeding trial, growth performance, proximate body composition, serum innate immunity and digestive enzymes activity were considered. Results showed that use of different levels of the bacterium significantly improved growth indices (P < .05). Those fish fed diet containing 10(8) E. faecium CFU g(-1) feed showed the highest final weight, weight gain and SGR along with the lowest FCR in comparison to control group (P < .05). Body protein content of the experimental groups received 10(7) and 10(8) E. faecium CFU g(-1) feed significantly increased (P < .05). Dietary inclusion of 10(6) and 10(7) E. faecium CFU g(-1) significantly increased serum total immunoglobulin content of the fingerlings (P < .05). Feeding with diet containing 10(8) E. faecium CFU g(-1) resulted in significantly increased serum alkaline phosphatase activity (P < .05). Intestinal digestive enzymes activity of those fish received diet included with 10(7) and 10(8) E. faecium CFU g(-1) feed significantly increased (P < .05). Moreover, the highest activity of lipase and protease were noticed in those fish received 10(8) E. faecium CFU g(-1) feed (P < .05). In conclusion, our results revealed beneficial effects of the host-associated bacterium isolated from adult Caspian roach intestine on growth performance, body composition, non-specific immunity and digestive enzymes activity of the fingerlings.