Cellulase activity in rohu fingerlings

The activity of cellulase was determined in the intestine of rohu, Labeo rohita, fingerlings fed on separate dietary formulations incorporating Leucaena leaf meal and synthetic cellulose at 20% level in proportional replacement of the ingredients from the fish-meal-based reference diet. Three more replicate experimental diets were prepared by incorporating 1% tetra-cycline, a broad-spectrum antibiotic, into the former three dietary formulations so as to circumvent the action of microflora in digestive function. Cellulase activity was found to be highest in fish fed on the cellulose incorporated diet, followed by those maintained on the plant-protein-based and reference diets, respectively. A diet-dependent variation in cellulase activity was apparent. However, a sharp decline in the level of cellulase activity was observed in the fish fed diets containing tetracycline, which is supposed to have destroyed all the gut microflora. The microbial culture of intestinal and hepatopancreatic extracts also confirmed the absence of microflora in the fish fed tetracycline-compounded diets. The study indicates that cellulase activity in rohu is largely contributed by the intestinal microflora, while the reduced activity recorded in the fish reared on antibiotic-compounded diets may be due to the presence of some other source of cellulase secretion apart from cellulolytic microbial action. The information generated from the present investigation might contribute towards better feed formulation for carp at low cost, incorporating plant-based feed ingredients. © Rapid Science Ltd. 1998