Insects are a pathway through which agro-food waste can become a high-quality source of nutrients for both livestock and humans. Yellow mealworm (Tenebrio molitor L., Coleoptera: Tenebrionidae) larvae are currently one of the insect species permitted for consumption, and they are reared on a large scale in Europe. This study evaluated the effect of seven diets containing byproducts such as wheat, rye bran, rapeseed meal, rapeseed cake, flax, and milk thistle cakes on the insect’s growth performance, feed conversion ratio (FCR), efficiency of conversion of ingested feed (ECI), nutritional quality of the larvae, and the composition of fats and fatty acids they contained. The lowest FCR based on the fresh and dry basis was 3.32 and 2.01, respectively. The ECI values were statistically different for larvae reared on different experimental diets (mean value 45.7%). As for the nutritional profile, protein and fats ranged from 43.6 to 53.4% d.m. and from 22.3 to 30.0% d.m., respectively. The major fatty acids in all samples were oleic acid (32.97–46.74% of total fatty acids (TFA)), linoleic acid (22.79–38.98% of TFA), and palmitic acid (12.80–17.81% of TFA). This study offers a new opportunity to use and efficiently convert cheap industrial byproducts using yellow mealworms.

Continued population growth could lead to protein deficiency in the human diet. To counteract this risk, attempts are being made to identify new edible sources of protein. The aim of this paper was to review the existing literature and to analyse the current state of yellow mealworm (Tenebrio molitor) rearing for food and feed, especially in Europe. The yellow mealworm is the most widely bred and traded insect species in Europe that has high feed conversion ratio; 3.4 to 6.1 kg of feed ingested per kg of harvested larvae. Mealworms could compete with livestock due to their high protein and fat content and low environmental impact. Mealworms have been extensively researched as a source of feed for animals, including poultry, fish, pets and birds. Its nutrient content depends on the processing method, where thermal processing is least desirable. Mealworms are characterised by a high and variable microbial load which has to be reduced before consumption. The antibiotics, pesticides and other substances should also be analysed to ensure that mealworms are a safe protein source for human consumption. The nutritional benefits of mealworms have to be communicated to European consumers who are generally averse to eating insects.