Probiotic effect of a live bacterial isolate in nutrition of an Indian major carp, rohu (Labeo rohita)

Use of probiotics as an efficient feed supplement is explained by feeding isolated probiotic strain to an Indian major carp, rohu (Labeo rohita). Two Bacillus strains (one non spore forming and the other spore forming), isolated from the gut of the carp, confirmed their probiotic effect by agar overlay method and antagonistic assay against three pathogenic strains which were incorporated in feed (protein - 40%) at graded levels of 5 X 107 cells g⁻¹ feed, 5 X 106 cells g⁻¹ feed and 5 X 105 cells g⁻¹ feed. Rohu fingerlings (Avg wt - 1.08 g), stocked in plastic circular troughs, were fed with the prepared feed @ 5% of body weight. Feeding trial was continued for 30 days, based on the biogrowth parameters and proximate composition of fish. The spore forming Bacillus incorporated at concentration of 5 X 106 cells g⁻¹ feed recorded the highest growth rate while at concentration of 5 X 107 cells g⁻¹ feed recorded the highest survival. There existed significant difference (P< 0.05) in growth rates between fish fed with spore forming Bacillus and non spore forming Bacillus as probiotic. However, the proximate composition analysis did not reveal significant differences between the fish fed with spore forming Bacillus and non spore forming Bacillus as feed probiotic. Supplementation of spore forming Bacillus in artificial diet improved the growth and feed conversion ratio of fish.