Growth performance and nutritional profile of mealworms reared on corn stover, soybean meal, and distillers’ grains

Mealworms are commercially reared on diets comprising of mixed grains. Substituting grains with agro-food industry by-products creates opportunities to valorize by-products and lowers the cost of insect rearing practices. In this study, three by-products (mushroom spent corn stover, highly denatured soybean meal, and spirit distillers’ grains) as treatments and wheat bran as control were used to rear mealworms. For growth performance, mealworms dry weights reared on three by-products were 53–67% of control. Feed conversion and utilization ratios ranged from 36 to 45% and 50 to 57% of control, respectively. For nutritional profile, protein and fat fractions ranged from 70 to 76% and 6 to 12% of mealworm dry weight, respectively. Leucine, lysine, methionine + cysteine, threonine, and valine were the limiting amino acids comparing with FAO/WHO requirements. The major fatty acids were linoleic acid (C18:2, 30–38%), oleic acid (C18:1, 24–34%), and palmitic acid (C16:0, 14–17%). The comparable nutritional profile demonstrated the potential to rear mealworms using these three cheap by-products. The results provide a reference for insect farmers to formulate the diets for obtaining specific insect products with desired nutrient composition.