Replacement of soybean meal in the diet of Nile tilapia (oreochromis Niloticus) by black soldier fly (hermetia illucens) larvae meal and the cost implications

Abstract

Soybean meal (SBM) is a plant protein derivative, which is widely used in Nile tilapia (Oreochromis niloticus) feed formulation. However, as a major plant protein source, SBM creates a food-feed competition with a growing demand for both aquaculture and terrestrial animals. In addition, soybean is characterized by deficiency in methionine and cystine, low nutrient digestibility and lesser nutrient bio-availability that limits inclusion levels hence compromising optimal fish growth. It is the limitations of SBM that have prompted search for other alternative protein sources, for fish feed production. This study investigated the effect of replacing SBM with black soldier fly larvae meal (BSFLM) on the growth performance, feed utilization, carcass body composition and amino acid concentration of O. 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 (8m3) each at a density of 12.5 fish m-3.The cages were suspended in earthen ponds (150 m2) with four cages per pond. Fish were hand fed at 5% (28 days), 3% (54 days) and 2.5% (84 days) of the body weight twice a day (1000hrs and 1600hrs). Significant differences (P < 0.05) were found in the final body weight, body weight gain (BWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate and Fulton’s condition factor (K). The best growth performance and feed utilization was recorded in fish fed on BSFLM100.The diets had significant (P < 0.05) effects on body composition and amino acid profiles of the experimental fish. Fish fed on BSFLM100 exhibited highest levels of crude protein of the fish carcasses with highest values for phenylalanine, threonine, Isoleucine, lysine, proline and glutamic acid amino acids. On enterprise budget analysis, replacing SBM with BSFLM at 50% and 100% reduced the cost of culturing O. niloticus by 8.8% and 12%, respectively compared to control diet COMM0. The study demonstrated that BSFLM is a cost-effective alternative to SBM in the diets of O. niloticus hence can replace soybean meal up to 100% without negative effect on growth and carcass body composition.