Supplementation of an isolated fish gut bacterium, Bacillus circulans, in formulated diets for Rohu, Labeo Rohita, fingerlings

Abstract

An extracellular protease producing bacteria Bacillus circulans (Lr 1.1) was isolated from the gut of rohu, Labeo rohita, fingerlings, and used as a supplement in five diets for rohu fingerlings. The effect of the supplement on the growth performance and feed utilization efficiency of the rohu was evaluated. Rohu fingerlings (avg wt 0.83±0.02 g) were fed diets supplemented with 1.5 × 104 (diet D2), 1.5 × 105 (diet D3), 1.5 × 106 (diet D4), 1.5 × 107 (diet D5) or 1.5 × 108 (diet D6) B. circulans cells per 100 g feed for 60 days at 3% of the body weight in triplicate treatments. The control diet (diet D1) was not supplemented with the bacteria. Diet D3 resulted in significantly better growth, a lower feed conversion ratio and a higher protein efficiency ratio than the other experimental diets. Intestinal α-amylase activity did not differ significantly beyond the lowest inclusion level (diet D2), whereas protease activity increased significantly with diets D2 and D3. Apparent dry matter and protein digestibility did not significantly correlate. However, lipid digestibility decreased with the increasing level of B. circulans.