Insect meal inclusion as a novel feed ingredient in soya-based diets improves performances of rainbow trout (Oncorhynchus mykiss)

Authors: HOSSAIN, SAKHAWAT - University Of Idaho; FAWOLE, FEMI - University Of Idaho; LABH, SHYAM - University Of Idaho; SMALL, BRIAN - University Of Idaho; Overturf, Kenneth - Ken; KUMAR, VIKAS - University Of Idaho

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2021
Publication Date: 6/26/2021
Citation: Hossain, S., Fawole, F., Labh, S., Small, B., Overturf, K.E., Kumar, V. 2021. Insect meal inclusion as a novel feed ingredient in soya-based diets improves performances of rainbow trout (Oncorhynchus mykiss). Aquaculture. 544:737096. https://doi.org/10.1016/j.aquaculture.2021.737096.
DOI: https://doi.org/10.1016/j.aquaculture.2021.737096

Interpretive Summary: Historically fishmeal (FM) has been considered the major protein protein source in aquaculture diets. However, increasing world wide demand and reducing supply of this finite protein source makes it a limiting factor in aquaculture production. In the research reported here we looked to reduce fishmeal by replacing it with sustainable protein sources and test the effectiveness of insect meal replacement at two levels. Several physiological parameters were measured including fish growth, relative levels of several fatty acids in the tissue, and the expression of genes linked to fatty acid processing and antioxidant potential. From our findings we concluded that insect meal inclusion at low levels is beneficial for increased growth, anitoxidant status and the restoration of certain critical fatty acids. These findings will be assist feed manufacturers and aquaculture producers in formulating sustainable and healthy feeds.

Technical Abstract: We evaluated the additive effects of insect meal supplementation to diets containing a high dietary inclusion of soy protein on growth performance, antioxidant potential and fillet nutritional quality of juvenile rainbow trout. A high level of soybean protein (21% of soybean meal, SBM plus 4-5.5% soy protein concentrate, SPC) based basal diet (Soy) supplemented with low (8%) and high levels (16%) of insect meal for diet groups Soy + IM Low, Soy + IM High, respectively. A high level fishmeal (24%) based positive control diet (Fish meal) was also produced. All diets were iso-nitrogenous (44%) and iso-lipidic (20%) and were fed to triplicate groups of rainbow trout juveniles (initial weight 32±0.0'g) over the course of a 10-week trial. Fish fed the positive control diet showed significantly higher final weight, % weight gain (%WG) and specific growth rate (SGR) compared to the Soy + IM High and Soy feed, but these parameters were not significantly different from the Soy + IM Low diet group. High soya based basal diet and Soy + IM High diet groups showed significantly lower final weight, % WG and SGR. Feed efficiency and protein efficiency ratio was numerically higher in fish fed the fish meal based positive control diet group followed by Soy + IM Low, Soya and Soy + IM High diet groups, respectively. Among somatic indices, condition factor (CF) was significantly influenced by IM supplementation and the Soy + IM High diet group showed significantly lower CF compared to other dietary groups. Addition of insect meal significantly increased whole body amino acids viz., arginine, histidine, valine and threonine content. Insect meal supplementation significantly increased muscle a-linolenic acid content. However, a-linolenic acid content in fish fed the Soy + IM High diet was not significantly different from fish fed the fishmeal based positive control diet. Insect meal supplementation did not significantly influence EPA+DHA, total n-3 PUFA and monounsaturated fatty acid content in the muscle, whereas the highest EPA/DHA and total monounsaturated fatty acids were detected in the fishmeal based positive control diet group. The liver gene expression pattern for '5 desaturase was significantly higher in the Soy + IM Low diet fish, while '6 desaturase and fatty acid synthase were significantly higher in Soy (basal) and Soy + IM Low diet fed fish. Elongase and fatty acid binding protein were not significantly influenced by insect meal supplementation. Regarding antioxidant potential Soy + IM High and Soy diet groups showed significantly higher and lower glutathione peroxidase (GPX) and superoxide dismutase (SOD) activity, respectively. Finally, we conclude that insect meal inclusion at a low level (8%) is beneficial for increased growth, antioxidant status and some fatty acids restoration in soy-based feeds for rainbow trout.