Self-selection of agricultural by-products and food ingredients by tenebrio molitor (coleoptera: tenebrionidae) and impact on food utilization and nutrient intake

Authors: Morales Ramos, Juan; Rojas, Maria - Guadalupe; KELSTRUP, HANS - Beta Hatch Inc; EMERY, VIRGINIA - Beta Hatch Inc

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2020
Publication Date: 11/24/2020
Citation: Morales Ramos, J.A., Rojas, M.G., Kelstrup, H., Emery, V. 2020. Self-selection of agricultural by-products and food ingredients by tenebrio molitor (coleoptera: tenebrionidae) and impact on food utilization and nutrient intake. Insects. 11:827. https://doi.org/10.3390/insects11120827.
DOI: https://doi.org/10.3390/insects11120827

Interpretive Summary: Insects have been considered as a potential replacement of fishmeal in animal feed. Nutritional content of insects have been found to be consistent with animal needs of essential amino acids and vitamins. However, current methods for mass producing insects are still expensive making insect products no so competitive in the market. One way to reduce costs of insect production is to lower the costs of the diet used to produce them. One way to approach this is by using agricultural by products as ingredients to formulate insect diets. In this study 20 ingredients were tested for their suitability to grow the yellow mealworm. These ingredients included dry potato and cabbage; the brans of wheat and rice; meals from the vegetable oil industry including canola, olive, sunflower, soy, and cotton; spent distillers grains including corn and wheat DDGS and spent brewery dry grain; and hulls of grains including rice, peanut, and oat. To test the large number of ingredients used, a method named self-selection was used to approach an optimal proportion of these ingredients for maximizing mealworm growth. This method consisted of presenting choices of multiple ingredients to groups of mealworms while carefully measuring the relative consumption of each ingredient, the weight gain of the mealworms and their waste. Food assimilation percentages and efficiency of food conversion were then calculated. Results showed that the most suitable ingredients for mealworm production were dry cabbage and potato, the brans of wheat and rice, meals of canola and sunflower, and distilled grains from corn and barley. This information will be used to formulate and evaluate diet formulations for the yellow mealworm in future research.

Technical Abstract: The method of nutrient self-selection was used to determine optimal intake ratios of macro-nutrients by Tenebrio molitor L. larvae. Self-selection experiments were established using nine different combinations (treatments) of 8 ingredients presented in a multiple-choice arena in a radial distribution to groups of 100 T. molitor larvae (12th – 13th instar). A total of 20 ingredients were tested provided in dry pelletized form. Larvae freely selected and feed on the ingredients for a period of 21 days at 27ºC, 75% RH, and dark conditions. Data consisting of weight consumption (g) of each ingredient and the larval live weigh gained (mg) were recorded from each repetition at the end of 21 days. The percent consumption of each ingredient within each treatment was calculated. Additionally, data of total food consumption, live weight gained, and frass production were used to calculate food assimilation and efficiency of conversion of ingested food (ECI). The optimal macro-nutrient intake ratios were 0.06 ± 0.03, 0.23 ± 0.01, and 0.71 ± 0.03 for lipid, protein, and carbohydrate, respectively based on the ratios observed in the best performing treatments. The intake of neutral detergent fiber (NDF) negatively impacted food assimilation, ECI and biomass gain. Food assimilation, ECI, and biomass gain were significantly impacted by the intake of carbohydrate in a positive way. Cabbage, potato, wheat bran, rice bran (whole and defatted), corn dry distillers grain (DDGS), spent brewery dry grain, canola meal and sunflower meal were considered suitable as T. molitor diets ingredients based on their relative consumption percentages (over 10%) within treatment.