Influence of Dietary Protein Content on the Nutritional Composition of Mealworm Larvae (Tenebrio molitor L.)

SIMPLE SUMMARY: Protein-rich insects are becoming more popular as livestock feed alternatives to fish and soy meal. A variation of different diets was used to rear mealworm larvae for the purpose of influencing their chemical composition. How dietary protein content affects larval protein and amino acid composition and growth rate was primarily investigated. Experimental diets used wheat bran as the control substrate, while different types of flour, notably pea protein, rice protein, sweet lupine, and cassava, along with potato flakes, were mixed with the wheat bran. Each substrate and larva were then analyzed for moisture, protein, and fat content, as well as the amino acid profile. A supplementation of pea and rice protein was determined to be most beneficial in terms of high protein yield and lower fat content in larvae. Cassava flour and wheat bran mixed together produced the highest amount of amino acid and essential amino acid content. Additionally, dietary fats and carbohydrates were found to have a greater influence on larval composition than protein content. This research could improve future formulations of artificial diets for Tenebrio molitor larvae. ABSTRACT: The use of insects as livestock feed is becoming increasingly accepted because they provide an important source of protein. The purpose of this study was to investigate the chemical composition of mealworm larvae (Tenebrio molitor L.) reared on a range of diets that differed in nutritional composition. Focus was placed on the influence of dietary protein content on larval protein and amino acid composition. For the experimental diets, wheat bran was chosen as the control substrate. The following types of flour-pea protein, rice protein, sweet lupine, and cassava, as well as potato flakes, were mixed with wheat bran and used as the experimental diets. An analysis of the moisture, protein, and fat content was then carried out for all diets and larvae. Furthermore, the amino acid profile was determined. It was shown that supplementing the feed with pea and rice protein was most suitable in terms of high protein yield in larvae (70.9–74.1% dry weight) with low fat content (20.3–22.8% dry weight). The total amino acid content was highest in larvae that were fed with a mixture of cassava flour and wheat bran (51.7 ± 0.5% dry weight), as well as the highest content of essential amino acids (30.4 ± 0.2% dry weight). Moreover, a weak correlation between larval protein content and diet was identified, yet a stronger influence of dietary fats and carbohydrates on larval composition was found. This research could result in improved formulations of artificial diets for Tenebrio molitor larvae in the future.