This study investigated the effect of replacing soybean meal (SBM) with black soldier fly larvae meal (BSFLM) on the growth performance, carcass body composition and profitability of Nile tilapia (Oreochromis niloticus). Three isonitrogenous (30% crude protein) diets containing BSFLM in varying proportions of 0% (BSFLM0), 50% (BSFLM50), and 100% (BSFLM100), were formulated to replace SBM. A commercial diet (COMM0) sourced from the local market was used as a positive control. Male sex-reversed O. niloticus juveniles of mean weight 20.88± 0.16 g were stocked in 12 cages each at a density of 12.5 fish m-3. Fish were hand fed at 5% of the body weight twice a day (1000 and 1600hrs) and thereafter adjusted to 3% and 2.5% for 6 months. The diets had significant effects on the final body weight, body weight gain (BWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate and condition factor (K) (P < 0.05). The best growth performance and feed utilization was recorded in fish fed on BSFLM100. The diets had significant effects on body composition and amino acid profiles of the experimental fish (P < 0.05).
An increase in BSFLM led to a significant decrease in crude protein, ash and dry matter of the fish carcasses with an increase in amino acids concentration. The carcass of the fish fed on BSFLM100 exhibited significantly highest values (P < 0.05) for methionine (5.0%) and lysine (56.3%) (essential amino acids) and alanine (8.9%), cysteine (8.0%) and proline (14.7%) (non-essential amino acids). Results from the partial enterprise budget analysis indicated that the total cost of feeding Nile tilapia BSFLM100 had significantly reduced and had higher gross profit compared to the conventional commercial feed (P < 0.05). This translated to positive return on investment for the feed containing 100% inclusion rate of BSFLM as a replacement of soybean meal therefore making BSFLM a highly sustainable and cost effective alternative protein ingredient in fish feed as it improves growth performance and feed utilization