The yellow mealworm (Tenebrio molitor) could be a could be a “critical alternative protein source” to replace conventional soymeal feeds in the diets of a range of livestock, according to a wide-ranging study.
The work, led by Prabhat Khanal at Nord University in Norway, analysed the nutritional profile, digestibility and microbiome of the beetle at all its life stages, when fed either a wheat- or oat-based diet.
He found that crude fat and many minerals were higher when the insects were fed the wheat-based diet, and that larvae and pupae had lower fibre, protein and amino acids than adults, but higher fat, fatty acids and energy levels. Amino acid content and available nutrients in larvae and pupae were similar to soybean meal.
Adult insects have potential, too
To test the digestibility of the reared mealworm by ruminants, Khanal employed a laboratory method using ruminal fluid from Holstein cows, while for other types of livestock which have only one stomach, he tested the feed products using a mixture of enzymes.
To date, most applications of mealworm as food or feed have utilised the larval stage of the insect, and he noted that the protein digestibility of adults was significantly lower than larvae and pupae — the juvenile stages being comparably digestible to soybean meal.
“Mealworm adults could be an important source of bioactive compounds with beneficial effects on animal health and immune function, but approaches to improve their digestibility and potential utilization must be identified,” he wrote in Journal of Cleaner Production.
Microbiome focus could reap rewards
The results of gut microbiome analysis also provided food for thought which could inspire further work.
Khanal found that the “rather simple set of microbes” can exhibit strong changes in response to nutritional challenges such as starvation, with some associated with antimicrobial activity and efficient use of nutrients recorded in greater numbers when the insects were fasted — a step generally taken during the harvesting and processing of insects.
The findings suggest that the gut microbiome could be exploited as a way of improving the efficiency of the bio recycling of substrates such as agricultural by-products.
“The present study provides a strong platform for further commercialization of the future mealworm production sector, exploiting mealworm biomass derived from different metamorphic stages,” he added.
