Dietary Evaluation of Lactobacillus acidophilus Strain PR2 as a Probiotic on Growth, Immunity, and Water Quality in Major Carp (Catla catla)

Abstract

Probiotic candidates, Lactobacillus acidophilus, are recognised for their ability to produce extracellular enzymes (proteases, lipases, and amylases), form resilient spores, inhibit pathogens, and colonise the intestinal mucosa. The present study investigated the dietary effect of a probiotic strain, Lactobacillus acidophilus, isolated from the gut of healthy fish, on the growth performance, feed utilisation, survival, and immune response of major carp (Catla catla) fingerlings. Four experimental diets were prepared with probiotic supplementation at 0% (control), 0.5%, 1.0%, and 1.5% inclusion levels. The eight-week feeding trial was conducted in a Completely Randomised Design (CRD) with triplicate groups. Results showed significant improvements (p < 0.05) in final weight, specific growth rate, weight gain percentage, protease and lipase activity, and feed efficiency in fish fed with 1.5% probiotic supplementation compared to the control. Survival rate did not differ significantly among treatments. The findings indicate that dietary supplementation of Bacillus sp. strain PR2 enhances growth and digestive enzyme activity, improving nutrient assimilation and immune modulation in major carp fingerlings. This probiotic strain demonstrates potential for sustainable aquaculture applications.  Therefore, Bacillus sp. strain PR2 represents an effective, natural, and eco-friendly probiotic candidate suitable for improving carp culture productivity while reducing reliance on antibiotics.