Optimization of housefly larvae production on pig wastes and brewers’ grains for integrated fish and pig farms in the tropics

Lack of appropriate animal waste management methods in many smallholder farms in the tropics often leads to environmental problems, especially in locations with high population density such as urban and peri-urban areas. On farms integrating pig production to fish farming, manure can be turned into a valuable feed source of high quality protein for fish through housefly larvae and contribute to intensify fish production and reduce cost of fish feed. Three experiments were carried to optimize operating conditions for maggot production on animal wastes and industrial byproducts found in Kinshasa, the capital city of the Democratic Republic of Congo (DRC). The comparisons were: (1) production on pure substrates (manure or brewer’s grains) or mixtures with lysine or blood; (2) exposure time to flies for the insemination of the substrates: and (3) dynamics of larvae production. Mixing brewers’ grains with Lysine or manure and/or blood more than doubled the amount of larvae that were harvested. Brewers’ grains are a good source of energy, but are probably deficient in essential amino acids to support the growth of maggots. It also appears that only the first days of laying eggs are important since no difference was observed between temporary and permanent exposure of the substrates to houseflies. The peak of larvae production was reached 6 days after exposure. The addition of cow blood in increasing doses to a mixture of brewers’ grains and manure linearly increased the production of maggots.