Black soldier fly larvae as a sustainable animal feed ingredient in Kenya

Abstract

Pig, poultry and fish farming are among the fastest growing agribusiness activities in East Africa, but high cost of major feed protein ingredients including fishmeal hampers profitability and growth of smallholder production. Interest in insects as an alternative nutrient source is growing. Black soldier fly (BSF) Hermetia illucens L. (Diptera: Stratiomyidae) is the most common insect species reared for animal feed. BSF larvae are able to exploit a wide variety of rearing substrates, including organic side streams, thus upgrading low-grade substrates into a high-quality protein source; BSF is not considered as a pest or vector of diseases and does not constitute a nuisance. These attributes make it an attractive insect species for mass production as sustainable and affordable feed ingredient. This thesis explores the potential of BSF as a novel feed ingredient in Kenya. The need to establish an insect-based feed sector has become important, but for insect-based feed to make a substantial contribution in substituting the conventional protein-rich fishmeal and soybean meal, large quantities of insect biomass are required, which makes insect mass rearing an inevitable step. Therefore, knowledge on sources of substrates for rearing BSF larvae, suitability of insect meal as feed ingredient, as well as acceptance and demand by end users is necessary for a sustainable insect-based feed sector. Promoting inclusive business for smallholder farmers through insect farming in an agribusiness value chain has been discussed. Farmers’ knowledge and willingness to pay for insect-based feed have been assessed. Larvae of BSF have been reared on agro-industrial by-products composed of brewers’ spent grains (BSGs), brewer’s yeast and cane molasses, their nutritional composition assessed, and have subsequently been fed to pigs. The results show that farmers are aware of insects as feed and are willing to use insect-based feed. BSGs are suitable for rearing larvae of BSF and supplementing BSGs with brewer’s yeast or molasses affects the crude protein or fat content of the larvae, respectively. Fishmeal has been replaced up to 100% with BSF larvae in feeds for growing and finishing pigs, demonstrating that these larvae are a suitable and affordable alternative to fishmeal with a beneficial return on investment, growth, carcass and nutritional quality of edible pork by-products. The study described in this thesis provides valuable insights into the suitability of combining different agro-industrial by-products for producing high-quality BSF larvae. These results are relevant to animal feed producers seeking to include insect meal in their feed formulae, to smallholder BSF farmers that either generate a circular production on-farm or sell BSF to feed millers. Finally this contributes to sustainable and economically viable livestock feeding systems.