Growth, fillet yield, and muscle quality traits are not affected by a genotype by environment interaction in rainbow trout consuming diets that differ in lipid content

Authors: Cleveland, Beth; Radler, Lisa; Leeds, Timothy - Tim

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2023
Publication Date: 5/1/2023
Citation: Cleveland, B.M., Radler, L.M., Leeds, T.D. 2023. Growth, fillet yield, and muscle quality traits are not affected by a genotype by environment interaction in rainbow trout consuming diets that differ in lipid content. Journal of the World Aquaculture Society. 1-15. https://doi.org/10.1111/jwas.12979.
DOI: https://doi.org/10.1111/jwas.12979

Interpretive Summary: Selective breeding has been applied in aquaculture to improve production traits, such as fillet yield. However, production traits are affected by both genetic and environmental factors, the latter of which can vary between grow-out locations. Critical for developing lines of fish with improved production traits is that these lines retain the improved trait(s) across a range of production conditions. Scientists at the National Center for Cool and Cold Water have created a line of rainbow trout with improved fillet yield. However, it is unknown if this line retains its high fillet yield trait when consuming a diets that vary widely in dietary fat content. Therefore this study determined how product yield and fillet quality respond in two lines of rainbow trout bred for high fillet yield versus low fillet fillet yield while consuming three commercial diets that contained low (18%), moderate (24%) and high (33%) fat content. While dietary fat content affected growth rate and product yield, higher carcass and fillet yield were consistently observed in the high fillet yield line of rainbow trout, regardless of dietary fat level. Also important was that breeding for high fillet yield did not have indirect negative effects on growth or fillet quality. These findings indicate that producers of the high fillet yield line can continue feeding their preferred dietary fat content, without losing the enhanced product yield trait or sacrificing growth performance or product quality.

Technical Abstract: Characterizing how selectively bred fish with improved production traits are affected by environmental factors is essential for realizing genetic gains in different production systems. In this study selectively bred rainbow trout (Oncorhynchus mykiss) with improved fillet yield were reared on three commercially available diets that varied primarily in dietary lipid/energy content: low lipid (LL, 18%), moderate lipid (ML, 24%), and high lipid (HL, 29 – 33%). The objective was to determine if a genotype by environment (diet) interaction affects product yield and muscle quality traits in a high fillet yield (HY) and low fillet yield (LY) line of rainbow trout. Main effects of genetic line (P < 0.05) were observed for fork length, for which the LY line was greater, and viscera yield, carcass yield, and fillet yield that were more favorable in the HY line. Muscle quality traits of lipid content, fillet color, and muscle cellularity and firmness also exhibited to main effects of genetic line (P < 0.05); findings indicated selection for fillet yield did not compromise fillet quality. Main effects of diet were consistently identified for growth, viscera yield, and indices of muscle quality (P < 0.05). A genotype by diet interaction (P < 0.05) was observed for viscera lipid content at the 2 kg harvest, for which viscera lipid content was similar between the HY and LY lines for the LL and HL diet, but greater (P < 0.05) in the LY line for the ML diet. Collectively, these findings indicate that higher product yields in the selectively bred HY line of rainbow trout will persist across diets with variable crude lipid/energy contents.