Effect of dietary synbiotic supplementation on growth, immune and physiological status of Labeo rohita juveniles exposed to low pH stress.

In this study, we tried to investigate the effect of dietary Bacillus circulans PB7 (BCPB7) and fructoligosaccharide (FOS), singly or in combination for evaluation of growth, immune and physiological status of Labeo rohita (rohu) juveniles reared under low pH and normal pH for 60 days. Experimental fishes were distributed in two sets such as one set continuously exposed to low pH (5.5) and other reared under normal pH (7.0), and fed with four iso-nitrogenous diets viz. basal (control), Bacillus circulans PB7 (BCPB7, 106 cfug-1 ), 1% fructooligosaccharide (FOS) and their combination. The effect of such pre, pro and synbiotics dietary treatments on growth performance (Weight gain %, specific growth rate, feed conversion ratio and protein efficiency ratio), immune response (hematological indices, serum biochemistry, lysozyme, NBT activity), antioxidative status in the form of antioxidant enzyme (catalase, superoxide dismutase, glutathione-S-transferase), acetylcholine esterase (AChE), Na+ K+ ATPase and stress bio-markers (cortisol, glucose and HSP-70) were examined. The group treated with low pH and fed with control diet (without supplementation) was noticeably inhibited (p < 0.01) in growth performance and immuno-physiological function of Labeo rohita. However, supplementation of BCPB7 and FOS was non-significant (p < 0.05) on growth performance and physiological process but the concurrent feeding of BCPB7+FOS remarkably improved (p < 0.01) growth and immune-physiological function of L rohita exposed to low pH. Overall results indicate that dietary combination of BCPB7+FOS can be an effective symbiotic formula against low pH stress in culture practices of L. rohita juveniles.