Growth parameters, nutritional content, and bacterial load and diversity found in the house cricket, Acheta domesticus L. reared on various diets composing of chicken feed, alfalfa/lucerne, and vegetable waste

To determine the effect of readily available diets on the rearing, nutrient content, and food safety of A. domesticus, fifty (50) first instar nymphs were reared over four (4) generations on maize/cornmeal/flour (MM), chicken feed (CF), alfalfa/lucerne (AL), chicken feed and alfalfa/lucerne (ALCF), vegetable waste (VW), or chicken feed and vegetable waste (CFVW). Although CF did not have the highest protein content, diets formulated with CF tended to have the best rearing performance compared to formulations with AL, the highest protein feed, reducing performance when used with CF. The worst-performing diets included MM and VW, which were thus inadequate for sustained rearing. Nutrient analysis showed that the protein content of the diet did not affect the nutrient content of A. domesticus. However, diets containing CF did have higher fat content along with lower associated costs of production. Conversion efficiencies were the best in diets containing CF, and despite being formulated for chickens, crickets still maintained higher conversion efficiencies. Total aerobic counts (TAC), which were used as an estimation of bacterial load, did not show any significant changes between diets, and all treatment averages were above the upper limit of safety according to European Commission Regulations No. 2073/2005. Generational changes were observed in growth period and adult mass, which worsened over time, while TAC improved in the final generation.

The bacteria present in A. domesticus were Enterobacter spp., Klebsiella pneumoniae, Bacillus spp., Citrobacter amalonaticus, Enterococcus spp., Tenebrionibacter intestinalis, Mammaliicoccus sciuri, and Serratia marcescens, of which the most commonly sampled are associated with the gut of edible insects that can aid in digestion and the breakdown of toxic material, although many of these and other bacteria are opportunistic pathogens that may contribute to antibacterial resistance. Other than Bacillus cereus, no other high-risk pathogens were identified in any of the samples. Ultimately, this study shows that A. domesticus rearing has the potential to be economically viable, but factors influencing long-term rearing need to be considered. The bacteria associated with A. domesticus do not pose a high risk for human health, but processing is needed to reduce TAC before they can be marketed for human consumption.