Growth, immune response, antioxidant capability, and disease resistance of juvenile Atlantic salmon (Salmo salar L.) fed Bacillus velezensis V4 and Rhodotorula mucilaginosa compound

Abstract A feeding trial of 62 days was conducted to investigate the effects of dietary administration of a probiotics compound consisting of Bacillus velezensis V4 CGMCC 10149 and Rhodotorula mucilaginosa CGMCC 1013 on growth, immune response, antioxidant capability, and disease resistance of juvenile Atlantic salmon ( Salmo salar L.) reared in a recirculating aquaculture system (RAS). Atlantic salmon were distributed in four equal groups, each with three replicates, which received one of the following experimental diets: Control (non-supplemented diet); T1 ( B. velezensis V4 5 × 10 6  CFU g −1 , R. mucilaginosa 5 × 10 7  CFU g −1 ), T2 ( B. velezensis V4 1.5 × 10 7  CFU g −1 , R. mucilaginosa 1.5 × 10 8  CFU g −1 ), and T3 ( B. velezensis V4 2.5 × 10 7  CFU g −1 , R. mucilaginosa 2.5 × 10 8  CFU g −1 ). Administration of the probiotics compound had significant effects on growth performance, feed utilization, immune response, and antioxidant capability of Atlantic salmon, and mortality was significantly reduced (P  Aeromonas salmonicida ( A. salmonicida ) and cumulative mortality was recorded for the next 7 days. The cumulative mortality was lower in Atlantic salmon fed with the probiotics compound, especially in the T1 group, compared to the control. These results demonstrated that multi-probiotics had beneficial effects as an antibiotic replacer in terms of growth performance, non-specific immune responses and disease resistance in salmon. The present study demonstrated B. velezensis V4 and R. mucilaginosa compound as a beneficial dietary probiotics for juvenile Atlantic salmon reared in a RAS with the capability of improving growth performance and enhancing disease resistance by immunomodulation.