Use of different microbial probiotics in the diet of rohu, Labeo rohita fingerlings: effects on growth, nutrient digestibility and retention, digestive enzyme activities and intestinal microflora

Six iso-nitrogenous (350 g protein kg-1) and iso-caloric (4100 kcal kg-1) diets with or without probiotics supplementation namely T1 (Basal feed (BF) without probiotics; control), T2 (BF + Bacillus subtilis and Lactococcus lactis), T3 (BF + L.lactis and Saccharomyces cerevisiae), T4 (BF + B.subtilis and S.cerevisiae), T5 (BF + B.subtilis, L.lactis and S.cerevisiae) and T6 (BF + heat-killed bacteria of B.subtilis, L.lactis and S.cerevisiae) were fed to Labeo rohita fingerlings (6.0 +/- 0.06 g) for 60 days in triplicate tanks (30 fish per tank). In all probiotic-supplemented diets, the probiotic concentration was maintained at 1011 cfu kg-1 feed. After 60 days of culture, the fish fed combination of three probiotics at equal proportion (T5) had higher (P < 0.05) growth, protein efficiency ratio, nutrient retention and digestibility and lower (P > 0.05) feed conversion ratio over other treatment groups. Total heterotrophic bacterial population in intestine was drastically reduced on 15th and 30th days of sampling than the initial value (0 day of sampling) for T3, T4 and T5 groups. Except T6, the gut colonization of respective probiotics, which were supplemented through the diets, was also increased up to 30 days of culture of fish and thereafter remained constant.