Improved digestibility of black gram leaf meal based diets for rohu (Labeo rohita) with supplementation of exogenous enzyme cocktail

Leaf meal is currently the most cost-effective source of protein and energy for use as a supplement in fish feed. The drawback associated with integrating it into the fish diet pertains to the presence of anti-nutritional elements that must be eliminated through a viable approach such as the addition of exogenous enzymes for achieving optimal fish production. Consequently, a 60-day feeding trial was conducted to evaluate the black gram leaf meal (BGLM) as a potential ingredient to replace de-oiled rice bran (DORB) in the diet of Labeo rohita juveniles and reported for the first time. Three hundred acclimatized juveniles (average weight 11 ± 0.09 g) were allocated randomly into ten treatment groups in triplicate. Ten iso-nitrogenous (32 %) and iso-lipidic (6 %) diets were made with varying degrees of BGLM inclusion by gradually replacing DORB without or with exogenous enzyme mixture (E) of protease, xylanase, and phytase at a ratio of 1:1:1 viz. Control (40 % DORB, 0 % BGLM), BG₁₀ (30 % DORB, 10 % BGLM), BG₂₀ (20 % DORB, 20 % BGLM), BG₃₀ (10 % DORB, 30 % BGLM), BG₄₀ (0 % DORB, 40 % BGLM) & CE (C + 0.1 % E), BG₁₀E (BG₁₀ + 0.1 % E), BG₂₀E (BG₂₀ + 0.1 % E), BG₃₀E (BG₃₀ + 0.1 % E), BG₄₀E (BG₄₀ + 0.1 % E) were prepared. Fish fed with BG₂₀E diet exhibited maximum growth rates, nutrient utilization and digestibility co-efficient of the diet (P<0.05) however these were similar in C+E treatment (P>0.05). Inclusion of 20 % or more BGLM without enzyme cocktail significantly (P<0.05) decreased the nutrient utilization and growth performance of L. rohita. The dry matter and nutrient digestibility of the experimental diet were significantly decreased (P<0.05) with the inclusion of 20 % or more BGLM in place of DORB, however supplementation of exogenous enzyme cocktail significantly increase (P<0.05) the digestibility and highest was recorded in BG₂₀E. The present study concluded that supplementation of exogenous enzyme cocktail (protease, xylanase, and phytase) increase the digestibility of BGLM and increases its inclusion level up to 30 % in the diet of L. rohita, however, 20 % BGLM supplemented with enzyme cocktail registered the best growth, nutrient utilization and digestibility coefficient of the diet.