Investigation of the suitability of three insect meals as protein sources for rainbow trout

Authors: OWENS, CHEYENNE - Us Fish And Wildlife Service; POWELL, MADISON - University Of Idaho; GAYLORD, T. GIBSON - Us Fish And Wildlife Service; CONLEY, ZACHARIAH - Us Fish And Wildlife Service; Sealey, Wendy

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2024
Publication Date: 3/5/2024
Citation: Owens, C.E., Powell, M.S., Gaylord, T., Conley, Z.B., Sealey, W.M. 2024. Investigation of the suitability of three insect meals as protein sources for rainbow trout. Journal of Economic Entomology. 117:4 1254-1260. https://doi.org/10.1093/jee/toae037.
DOI: https://doi.org/10.1093/jee/toae037

Interpretive Summary: Insects are part of the natural diet of fish and may be viable alternatives to fish meal, which has been traditionally used as the main protein source in the aquafeed industry. However, differences in protein quality are known to exist among various insects. To effectively utilize various insects as alternative protein sources in rainbow trout feeds, USDA ARS nutritionist collaborated with US Fish and Wildlife service researchers to measure the protein and amino acid content of cricket meal, yellow mealworm meal and wax worm meal. The nutritional values of the examined insects suggests that cricket meal and yellow mealworm meal show promise as alternative protein sources in rainbow trout feeds, with the potential of waxworm meal as an alternative lipid source. Identification of alternative protein and lipid sources for rainbow trout feed can improve sustainability of the trout industry by reducing dependence on the limited quantities of wild-caught fishmeal and fish oil.

Technical Abstract: An in vivo trial was conducted to determine the apparent digestibility coefficients (ADC) for dry matter, crude protein, crude fat, and energy and to determine the apparent availability coefficients for amino acids and phosphorus of insect meals for rainbow trout. Rainbow trout (approximately 370 g ± 23 g, mean ± SD initial weight) were stocked 25 fish per tank into 200-L poly tanks. Water temperature was maintained at 15 ºC in a recirculating system. Lighting was maintained on a 13:11 h diurnal cycle. Fish were fed either a reference diet, or one of five different test diets created by blending the reference diet with each of the test ingredients (Menhaden fishmeal, special select (MFM), two cricket meals (Cricket A and Cricket B), waxworm meal, mealworm meal, in a 70:30 ratio (dry-weight basis). Diets were randomly assigned to three replicate tanks and hand-fed twice daily to apparent satiation for 14 days prior to fecal collection by manual stripping. Fecal samples were freeze-dried and homogenized prior to analysis. Ingredients, diets, and fecal matter were analyzed in duplicate for proximate, mineral and amino acid composition. Cricket meals contained similar protein (CP) and lipid (CL) levels (67 and 69% CP and 16.6% and 17.1% CL, for cricket A and B, respectively). Mealworm meal contained 56.5% CP and 27.7% CL, and waxworm meal contained 32.5% CP and 54.2% CL. Cricket and mealworm meals had similar analyzed composition and ADCs to MFM for dry matter, lipid, protein, and gross energy. Examined insect meals also had higher phosphorus availability than MFM. These nutritional values suggest cricket and mealworm show promise as alternative protein sources in salmonid feeds, with the potential of waxworms as an alternative lipid source warranting further investigation in growth trial.