Productivity of black soldier flies (Hermatia Illucens) fed on brewery waste, at varying stocking densities and turning frequencies
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Increased costs of production for fish protein feeds have led to development of potential alternatives for protein sources such as Black soldier fly (BSF). Brewery waste substrate derived from organic by-products is suitable for largescale production of insect meal. This study was examined to fill the knowledge gap on the effect of stocking density and turning frequency on the growth performance of Black soldier fly larvae fed on brewery waste substrate. The study was a 21 day experiment carried out in a greenhouse at ARDC Kajjansi Wakiso district Uganda. The BSF egggs were inoculated in the brewery waste at varying stocking densities that is; 0.02 g, 0.04 g, 0.06 g placed in rectangular plastic cans of area 500cm2. The treatments were subject to different turning frequencies that is unturned, turn once and turn twice giving 9 treatments which were replicated thrice to make a total of 27 replicates.The results from this study showed that treatments which were frequently turned have higher effect on the growth performance of BSFL than stocking density of BSF eggs. This was showed by the significant effect of turning frequency on specific growth rate (P=0.02, F=8.719, df =2). Regardless of the BSF stocking density, turning frequency significantly affected the specific growth rate of BSFL (P=0.02, F=8.71, df =2); being (0.12 ± 0.01) for no turning, (0.17 ± 0.01) where there was single turning and (0.19±.01) where there were two turnings. There is no significant effect of stocking density on specific growth rate (P > 0.05) however; there is an interaction effect of the stocking density and turning frequency on specific growth rate. Growth (Body length & mass) increases rapidly upon hatching and then remains constant as it tends to pre-pupae stage upon formation of cuticle on the skin of the insect. However, this growth is faster at lower stocking densities and higher turning frequency increases the survival rate, weight gain of BSF grown maintained on brewery waste substrate. Turning frequency and stocking density have an effect on growth performance of BSFL maintained on brewery waste although turning frequency of substrate has a higher effect than stocking density of BSF eggs.