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

Authors: Morales Ramos, Juan; Rojas, Maria - Guadalupe; DOSSEY, A - All Things Bugs, Llc

Submitted to: Journal of Insects as Food and Feed
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2018
Publication Date: 3/5/2018
Citation: Morales Ramos, J.A., Rojas, M.G., Dossey, A.T. 2018. Age-dependent food utilization of Acheta domesticus (Orthoptera: Gryllidae) in small groups at two temperatures. Journal of Insects as Food and Feed. 4(1):51-60. https://doi:10.3920/JIFF2017.0062.

Interpretive Summary: The house cricket is one of the most important insect species being produced commercially in the United States for animal feed and human consumption. In more recent years, growing interest in the use of insects as food and feed has opened new markets for crickets. Several companies in the U.S. and overseas are currently processing crickets to produce insect protein powders for human consumption to be used in the manufacturing of different food items including energy bars, corn chips, cookies, etc. An estimated annual house cricket production of 1,680 tonnes in the U.S. comes from 10 largest producers. 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 to establish an optimal harvesting age. Two temperature treatments of 80.6 and 84.2°F 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. Crickets grew larger at 80.6° and more biomass was produced at this temperature than at 84.2°, but also more food was consumed and growth rate was slower at 80.6° than at 84.2°. Group weekly gain of live biomass peaked at the end of week 8 at 80.6° (182.4 ± 23.38 mg/wk) and at the end of week 6 at 84.2° (128.75 ± 20.77 mg/wk). Based on these results we concluded that the optimal times for the harvest of farmed house crickets are at the end of week 6 at 84.2° and week 8 at 80.2°. However, the curves of productivity estimates seem to suggest that production could still be economical for an additional week in both temperatures as productivity values continued increasing.

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