Growth Performance and Carcass Characteristics of the African Catfish (Clarias Gariepinus) Reared on Diets Containing Black Soldier fly (hermetia illucens) Larvae Meal

Abstract

Fish feed protein ingredients are the most expensive and often unavailable in subSaharan Africa especially in commercial aquaculture systems. The major fish feed protein ingredient in fish farming in Kenya is fishmeal (FM) that is often times expensive and adulterated leading to low productivity of fish farming. This problem has necessitated a need for exploring alternative less expensive and easily available protein sources such as black soldier fly larvae (BSFL). This study aimed at evaluating the growth rate, feed utilization, survivability and carcass characteristics of the African catfish (Clarias gariepinus) reared on diets containing BSFL meal as a replacement for FM. Treatment diets were formulated for BSFL meal to replace FM at the rate of 0% (C), 25% (D1), 50% (D2), 75% (D3), 100% (D4) and D5 (49% BSFLM, 49% FM and 2% Baker’s yeast). All diets were formulated to meet the nutritional requirements of catfish. The catfish were housed in harper nets each measuring 2 by 2 by 2 meters and the net had one millimeter perforations to allow proper circulation of water and also prevent escape of the catfish. Each harper net held 20 pieces of catfish. The experiment was laid out in a completely randomized design with each treatment being replicated three times. The performance of the catfish was determined by recording the weights, lengths and mortality biweekly for six months. Analysis of variance was carried to determine the effects of the treatment diets on the weight gain, length gain and carcasses charateristics. Water quality parameters including dissolved oxygen, temperature, salinity and conductivity measured were within the optimum levels recommended for rearing the African catfish. Catfish consuming diets with 50% and 75% BSF larvae meal had the highest growth rates of 1.01g/day and 0.98g/day respectively. However, the growth rates of the catfish consuming the diets with 0% and 100 % BSFL meal as well as the diet containing 2 % baker’s yeast were not significantly different (P>0.05). Mortality of 1.10% was noted in the catfish consuming the control diet and diet containing 25 % BSFL but there was no mortality for the other treatment groups. Carcasses of African catfish fed treatment diets with BSFL meal had significantly (P<0.05) higher amounts of crude protein (CP) especially for D2 and D3. Ether extracts from the carcasses showed that an increase in BSFL meal led to an increase in the lipid content of the carcasses. The inclusion of BSFL meal did not negatively affect the nutritive composition and carcass quality (especially essential amino acids) of the African catfish. The study noted that the concentration of essential amino acids increased as the amount of BSFL meal in the diets increased. Substitution of BSFL meal for FM in the treatment diets didn’t negatively affect the survival rates of the catfish. The study recommends the use of BSFL meal at substitution rates of 50% and 75% for better survival and enhanced growth performance of African catfish as well enhanced quality of its carcass.