Product Quality of Field Crickets (Gryllus bimaculatus) and Black Soldier Flies (Hermetia illucens)

Abstract

Insect rearing provides an affordable alternative source of animal feed and human food to some small-scale farmers. However, current rearing technology, under uncontrolled environmental conditions, suppresses yields leading to low rearing of black soldier flies and crickets. The objective of this study was to assess the effect of optimized rearing conditions, using an adaptive control system, on the yield of field crickets (Gryllus bimaculatus) and black soldier flies (Hermetia illucens). This project was intended to actualize an optimized insect facility through control of environmental temperature, relative humidity, and ventilation rates. The approach entailed the construction of a modified rearing structure that is devoid of environmental setbacks to improve insect yields. The performance of the developed adaptive rearing structure was evaluated at no load and under loaded conditions. It was then optimized based on the most favorable parameter levels to attain better production of crickets and black soldier flies. Temperatures ranging between 25˚C to 30˚C; relative humidity ranging between 50% and 70% and an air speed of 3 m/s were adopted for the entire study. Besides optimization of wet yield, it is also critical to dry the harvested insect yield to quantify the dry matter content. The relationship between the dried weight of insects and the dry matter was used to quantify the weight loss incurred after the drying process. The study was conducted in Jomo Kenyatta University of Agriculture and Technology, Kenya. Black soldier fly larvae and adult crickets were harvested at the age of two and six weeks respectively. They were then oven-dried at 105˚C for 24 hours for subsequent analysis of proteins. Results indicated that black soldier flies’ larvae reared at 25˚C, 27˚C, and 30˚C had a maximum mean wet yield of 0.216 ± 0.022 g, 0.234 ± 0.019 g and 0.248 ± 0.016 g, respectively at the age of two weeks. Similarly, crickets reared at 25˚C, 27˚C, and 30˚C had a mean yield of 0.807 ± 0.167 g, 0.933 ± 0.102 g and 1.306 ± 0.254 g at the age of six weeks. Dried crickets reared at 25˚C, 27˚C and 30˚C had 25.566 ± 0.012%, 46.811 ± 0.647% and 58.216 ± 1.510% protein, respectively. On the other hand, black soldier flies reared at 25˚C, 27˚C and 30˚C yielded 42.655 ± 1.732%, 47.121 ± 0.015% and 62.536 ± 0.014%, respectively. Larval yield recorded significantly different yields (F = 4.935, p = 0.03) whereas crickets failed to record any significant difference in yields (F = 0.777, p = 0.388) under different temperature levels. A modeled relationship between input variables indicated a suitable input variable mix that can ensure sustainable production. The findings of this study demonstrate that optimal temperature and relative humidity promotes sustainable insect production.