Amino acid digestibility and protein quality of mealworm-based ingredients using precision-fed cecectomized rooster assay

Mealworms may serve as an alternative protein source for pet foods because of their high protein content and low environmental footprint. The amino acid (AA) content and protein quality of mealworm-based ingredients may vary depending on their composition and processing, however, so testing is required. Our objective was to measure the AA composition, AA digestibility, and protein quality of mealworm-based ingredients using the precision-fed cecectomized rooster assay. The University of Illinois Institutional Animal Care and Use Committee approved all animal procedures prior to experimentation. Sixteen cecectomized roosters (4 roosters/substrate) were randomly allotted to one of four test substrates: 1) whole lesser mealworm (A. diaperinus) meal (ADw); 2) defatted lesser mealworm (A. diaperinus) meal (ADd); 3) defatted yellow mealworm (T. molitor) meal (TMd); 4) hydrolyzed T. molitor protein meal (TMh). Ingredients were provided by Ynsect, France. After 26 h of feed withdrawal, roosters were tube-fed test substrates. Following crop intubation, excreta samples were collected for 48 h. Endogenous loss corrections for AA were made by using 5 additional cecectomized roosters. All data were analyzed using SAS version 9.4. All substrates had high AA digestibilities, with all indispensable AA digestibilities being >90% with the exception of histidine (87.9%-91.1%) and valine (77.9%-79.7%). Amino acid digestibilities were not different among substrates (P>0.05). Digestible indispensable AA score (DIAAS)-like values were calculated to determine protein quality according to Association of American Feed Control Officials (AAFCO) nutrient profiles, The European Pet Food Industry Nutritional Guidelines (FEDIAF) nutritional guidelines, National Research Council (NRC) recommended allowances for adult dogs, adult cats, growing puppies, and growing kittens, and NRC minimal requirements for growing puppies and growing kittens. In general, TMh had the highest and TMd had the lowest DIAAS-like values for most indispensable AA. Methionine (TMh; TMd; ADw) and phenylalanine (ADd) were the first-limiting AA. Our results demonstrate that mealworm-based ingredients are high-quality protein sources. Further research in dogs and cats is necessary to confirm sufficient palatability and digestibility, but these data suggest that they are valuable sources of protein for pet foods.