Farmed cricket performance remains stable over five generations of rearing on a waste-based diet
Farmed insects like crickets offer a sustainable protein source to feed the growing global population. A benefit of cricket farming is the potential to use waste diets instead of unsustainable, expensive feeds. Brewers spent grain is a nutritionally valuable organic waste product that has been used to rear crickets in single generation studies. However, the long-term effects of spent grain-based feeds are unclear, which makes incorporation into commercial feed risky for producers. We reared a farmed cricket (Gryllodes sigillatus) for five generations on a high inclusion (75%) spent grain diet. Crickets reared on spent grain were 18.5% smaller at adulthood than control crickets reared on farm feed, resulting in decreased yield (mass of crickets harvested), but were able to reproduce and had high survival rates. Cricket performance remained stable over five generations, indicating that spent grain contains adequate nutrition to support long-term cricket production. We also reared crickets on a gradual inclusion spent grain diet that increased from 15-75% spent grain over five generations. While this "weaning" approach did not improve cricket performance on high-inclusion spent grain diets, crickets on low inclusion diets (15-30%) displayed nearly a 30% increase in survival and yield compared to those fed the control. Therefore, inclusion of low amounts of spent grain in cricket feed may not only be beneficial from an environmental and feed cost perspective, but also from a production yield perspective. Our findings are the first to show that spent grain is a suitable feed ingredient for long-term rearing of farmed crickets.