Breeding salmonids for feed efficiency in current fishmeal and future plant-based diet environments

Area of Science:

• Aquaculture genetics
• Animal breeding
• Fish nutrition

Background:

• Aquaculture increasingly uses soybean meal (SBM) instead of fishmeal for carnivorous fish.
• This dietary shift may introduce genotype-environment (G x E) interactions, impacting fish performance.
• Evaluating the efficacy of existing breeding programs under novel diets is crucial.

Purpose of the Study:

• To determine if current salmonid breeding programs, optimized for fishmeal diets, enhance performance on soybean meal (SBM) diets.
• To assess the extent of genotype-environment (G x E) interactions in response to dietary changes.
• To evaluate the genetic basis of growth and feed efficiency traits in European whitefish fed different diets.

Main Methods:

• A split-family design was used with 1680 European whitefish from 70 families.
• Fish were fed either fishmeal- or SBM-based diets, and individual daily gain (DG), daily feed intake (DFI), and feed efficiency (FE) were recorded.
• Heritability, genetic correlations, and predicted genetic responses were analyzed to understand G x E interactions and breeding program effectiveness.

Main Results:

• Genotype-environment interactions were weak, with minimal differences in trait variances and heritabilities between fishmeal and SBM diets.
• Cross-diet genetic correlations for growth and feed efficiency traits were near unity.
• Daily feed intake (DFI) showed moderate heritability and a high genetic correlation with daily gain (DG); feed efficiency (FE) had low heritability.
• Selection for increased DG and FE on fishmeal diets predicted favorable responses on SBM diets.
• Index selection for FE, incorporating DG and DFI, yielded double the FE gain compared to selection on DG alone.

Conclusions:

• Existing salmonid breeding programs are effective in improving performance on soybean meal (SBM) diets, indicating robustness across dietary environments.
• The minimal G x E interactions suggest current breeding strategies can support the aquaculture industry's transition to sustainable, plant-based feed ingredients.
• Breeding programs can be optimized by using selection indices that include both growth and feed intake to maximize feed efficiency gains.