Age-dependent food utilisation of Acheta domesticus (Orthoptera: Gryllidae) in small groups at two temperatures

Insects hold potential as a sustainable source of animal protein. In recent years a new and rapidly growing industry of insect-based foods has emerged. The house cricket, Acheta domesticus (L.) (Orthoptera: Gryllidae), is one of the most important insect species being produced commercially in the USA for feed and food. However, the price of cricket powder remains much higher in comparison with other animal sources of protein. This study seeks to contribute to reduce cricket production costs by determining food conversion efficiency at different ages as a mean of establishing an optimal harvesting age. Two temperature treatments of 27 and 29 °C consisting of 27 groups of five crickets each were monitored weekly to measure food consumption and growth for a period of 10 and 9 weeks respectively. Data were used to calculate efficiency of conversion of ingested food (ECI) for each week and treatment. Crickets at 27 °C produced more biomass and adults were significantly larger than those developing at 29 °C. The peak individual weekly biomass gain was observed at the end of 8 weeks at 27 °C (87.9±8.1 mg) (mean ± SEM) and at the end of 6 weeks at 29 °C (51.4±7.1 mg). Mean ECI values during weeks 1 to 8 at 27 °C (20.7, 22.6, 22, 20.8, 21.6, 20.9, 20, and 16.5%) and weeks 1 to 6 at 29 °C (18, 24.4, 19.9, 18.9, 21.1, and 16.4%) did not differ significantly. Decline of ECI values was better explained by the increase in adult proportions than by mortality. The optimal age to harvest based on food consumption and cricket biomass gain ratios was at the end of 8 weeks at 27 °C and at the end of 6 weeks at 29 °C. An economic analysis resulted in slightly higher profits ($ 1.04 USD) per g of hatchling/year at 27 °C.