Nutrient Digestibility and Digestive Enzyme Activity in Fringe Lipped Carp, Labeo fimbriatus (Bloch, 1795), Fed Diets Containing Cottonseed Meal

Advanced fingerlings of Labeo fimbriatus (Bloch, 1795) were reared in aerated indoor plastic tanks to elucidate the dry matter and nutrient digestibility of cottonseed meal (CSM) in the feed. The fish were fed isocaloric formulated diets containing CSM replacing the main ingredients – groundnut cake and rice bran of the control diet at 10, 20, 30 and 40 % levels. Total dry matter digestibility and major nutrient digestibility were estimated using acid insoluble ash as the marker. In general, the digestibility of dry matter, protein, fat, and nitrogen-free extract was higher in CSM incorporated diets than the control diet. While the dry matter and nitrogen-free extract digestibility values were highest at 40 % CSM incorporation level, those for protein and fat digestibility were highest in 30 % and 10 % levels, respectively, showing an apparent reduction thereafter. The incorporation of CSM had a stimulatory effect on most of the intestinal digestive enzymes tested. Fish fed 20 % CSM diet recorded the highest activity of total protease and carboxypeptidases while those fed 30 % CSM diet had highest trypsin and amylase activities; all showing reducing trend consequently. In the case of hepatopancreas, the reducing trend in the activities of protease, chymotrypsin, carboxypeptidase A, and lipase observed with increased incorporation levels of CSM was significant (P < 0.05) and the reduction in the activities of trypsin, amylase and cellulase in CSM fed fish was not significant (P > 0.05). The study indicates the possibility of incorporation of CSM in the diet of L. fimbriatus up to 40 % level without affecting nutrient digestibility.