In vitro evaluation of fermentation characteristics of two types of insects as potential novel protein feeds for pigs

Novel protein sources such as insects are suggested for pig nutrition. Protein availability might be impacted by the nature of the insect and by the thermal treatment applied to sanitize this ingredient. Their influence on protein availability and colonic fermentation is unknown. Plant proteins (beans, lentils, peas, and soybean, raw and vapor cooked) were compared to adult house crickets (Acheta domesticus) and mealworm larvae (Tenebrio molitor) that had been autoclaved, oven cooked (150 and 200°C), or used raw. Ingredients were run in an in vitro model of the pig gastrointestinal tract combining enzymes to simulate digestion in the stomach and the small intestine and subsequent fermentation by fecal microbes to simulate hindgut fermentation. In vitro crude protein disappearance (IVCPD) of insects decreased with oven cooking at 150°C or autoclaving (P < 0.05) while that of plants was unaffected (P > 0.05), except for soybean. IVCPD of raw mealworms (0.726) equaled that of the best plants (0.725 to 0.763) while crickets were less digestible (P < 0.01). Consequences on fermentation metabolites were lower propionate (P < 0.01) and branched-chain fatty acids (BCFA; P < 0.05) molar ratio in raw insects against oven-cooked or autoclaved insects. Both insect sources displayed greater BCFA (P < 0.01) and lower propionate (P < 0.01) than plants. Crickets produced 50% as much BCFA as mealworms (P < 0.01). In conclusion, feeding insect-sourced protein requires a careful choice of the species as well as the thermal treatment to avoid possible detrimental consequences on digestibility and intestinal health in pigs.