Immune modulation, disease resistance and growth performance of Indian farmed carp, Labeo rohita (Hamilton), in response to dietary consortium of putative lactic acid bacteria

Probiotic effect of a consortium of putative lactic acid bacteria on Labeo rohita was investigated with emphasis on growth performance, immune response, and disease resistance against Aeromonas hydrophila. Fish were fed either a lactic acid bacteria-supplemented diet or a control diet for a period of 30 days. At the end of the experiment, probiotic fed group showed a significant improvement in weight gain percentage, specific growth rate, and feed conversion ratio along with increased respiratory burst activity of blood phagocytes and serum antiprotease activity level. Quantitative real-time PCR showed significant upregulation of IL-10 gene in kidney, intestine, and liver of probiotic-treated group, whereas TNF-alpha gene was significantly upregulated only in liver and intestine. HSP70 gene was significantly upregulated in intestine but downregulated in liver on day 15. Challenge with Aeromonas hydrophila on day 30 of probiotic feeding showed a significant increase in survival percentage of treated (93.33 %) over the control group (33.33 %). Further challenge after 20 and 40 days of withdrawal of probiotic showed higher survival percentage (60 and 40 %, respectively) in withdrawn group compared to control although difference was statistically insignificant. The consortium of putative probionts may serve simultaneously as an immunomodulating feed additive useful for disease protection and growth enhancer in eco-friendly freshwater aquaculture practices. However, feeding at regular interval with probiotic supplemented diet is suggested for a prolonged immunity.