Dietary Curd-fermented Rice Bran Improves Growth, Digestibility and Nutrient Utilisation in Labeo gonius (Hamilton, 1822) under Hill Aquaculture Conditions of Meghalaya, India

Abstract

Background: Rice bran has limited nutritional utility in carp diets owing to high crude fibre and phytic acid content, which fermentation can effectively reduce. The present study evaluated the effect of dietary curd-fermented rice bran (FRB) at graded inclusion levels on growth performance, organ indices, digestibility and muscle composition of Labeo gonius fingerlings under hill aquaculture conditions of Meghalaya. Methods: Three isoproteic (~25% crude protein) and isolipidic diets, T1 (0% FRB, control), T2 (50% FRB) and T3 (100% FRB), were fed to fingerlings (initial mean weight 5.42±0.31 g; 30 fish/tank) over 60 days in a completely randomised design with three replicates. Rice bran was fermented using fresh curd (Lactobacillus spp., 10 % w/w) and baker’s yeast (Saccharomyces cerevisiae, 3 % w/w) at 25±2°C for 48 hr under near-anaerobic conditions, reducing crude fibre from 12.60% to 9.20% and increasing crude protein from 12.20% to 15.80%, with pH declining from 6.2 to 4.0 confirming active fermentation. Result: T3 recorded the highest SGR (2.45±0.06%/day) and ADC for crude protein (86.1±2.2%), with the lowest FCR (1.98±0.06) and HSI (1.44±0.11%), while muscle crude protein was significantly highest in T3 (61.4±1.1% dw); all growth and digestibility parameters differed significantly (p≤0.05) among treatments, with survival and water quality remaining unaffected across dietary groups. These findings indicate that complete replacement of unfermented rice bran with curd-fermented rice bran improved growth performance, feed conversion efficiency and nutrient digestibility in L. gonius under Meghalaya hill aquaculture conditions.