Fish meal (FM) is the primary ingredient of the farmed fish feed. However, the decline in wild fish catches and the growing demand for the aquafeed resulted in a dramatic reduction of FM supply with increased cost. Black Soldier Fly meal (BSFM) is a promising animal-based protein for FM replacement because of its sustainable growth, environmentally friendly, low operation cost and highly nutritional profile. By considering its importance, this research was carried out to evaluate the efficacy of 30% and 45% fish meal replacement with Black Soldier Fly meal on growth, digestive enzymes activity and intestinal morphology of Nile Tilapia. The experimental trial was of 4 months and fingerlings were fed on 35% crude protein @6% of their body weight. Three groups were made: T0 (control group), having 100% FM with 0% BSFM replacement, T1 (30% FM replacement with BSFM) and T2 (45% FM replacement with BSFM). The evaluation of growth performance showed that the maximum weight gain of the fish was in T0 (67.4±1.58), as compared to T1(65.9±1.69) and T2 (60.1±1.75). The length gain was recorded highest in the control group (19.7±0.12), followed by T1 (18.4±0.19), while the lowest value was in T2 (17±0.17). Similar results were observed in specific growth rate, where the maximum values were recorded in T0 (2.6±0.12), as compared to T1 (2.2±0.13) and T2 (2.0±0.11). The lowest FCR value was in the control group (1.6±0.10), while the FCR value increased with increasing BSFM in T1 (1.8±0.11) and T2 (2.1±0.14). The survival rates remained highly significant in all treatment groups. The digestive enzymes activity of protease, amylase and lipase was analyzed at the end of the experimental period. The highest protease activity was recorded in T0 (10.2±0.17), followed by T1 (9.2±0.12) and T2 (8.3±0.15). The amylase activity was maximum in the control group (3.9±0.19), while in the experimental group, the activity decreased in T1 (3.5±0.12) and T2 (2.9±0.15). The maximum lipase activity was observed in T0 (4.0±0.12), as compared to T1 (3.4±0.18) and T2 (3.2±0.15). The investigation of intestinal morphology showed that the villi length and width decreased with increasing BSFM incorporation in fish feed. The villi length in the control group (170.1±1.41) was recorded as the highest, followed by T1 (166.5±1.23) and T2 (161.1±1.37). Similarly, the maximum villi width was in T0 (90.9±1.15) as compared to T1 (86.3±1.24) and T2 (82.1±1.50). Physico-chemical parameters such as temperature, dissolved oxygen and pH were maintained throughout the trial period. The overall findings showed that 30% Black Soldier Fly meal could be used as an alternative to fish meal in Nile Tilapia feed without compromising growth, digestive enzymes activity and intestinal morphology of fish.
Key words: Nile Tilapia, Fish meal replacement, Black solder fly meal, intestinal morphology, digestive enzyme.