Sustainability & efficiency

New approaches for environment-customized genetic selection

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Abstract

Genetic evaluations play a critical role in identifying genetically superior candidate parents for the next generation, by disentangling genetic from non-genetic effects on observed traits. Genetic evaluations have driven major improvements in livestock performance, leading to steady improvements in production, efficiency, health, and fertility traits. While challenges such as separating genetic merit from observed phenotypes, and optimally balancing antagonistic trait selection have largely been addressed, current genetic evaluations generally assume that genetic merit is independent of environment. However, when present, genotype-by-environment (GxE) interactions can alter rankings of selection candidates depending on environmental conditions experienced by their offspring. Although GxE effects on individual traits may seem modest, their impact becomes significant when selection relies on a unified selection index (USI) that combines multiple traits. Even small changes in breeding values can lead to substantial re-ranking of candidates on the overall index. Furthermore, GxE interactions are expressed not only by a change in the individual's estimated breeding values at the different environments, but they may also affect genetic parameters, including heritabilities and genetic correlations. Previous studies that accounted for GxE interactions across the scale of the temperature-humidity-index (THI) on the French Holstein and Montbeliarde dairy cattle populations, for example, have shown that heritabilities for protein yield and conception rate, as well as genetic correlations between these traits, vary depending on the THI experienced by the animals. In the context of USI-based selection, such changes in genetic parameters across different environments is also relevant, since the USI consists of a weighted sum of the traits of interest in a breeding program, and these weights are mostly defined by the trait's economic weights and genetic parameters. Moreover, the relative weights on traits that compose the USI are calculated to maximize their correlation with the defined breeding goals, generally applied to entire national populations or large populations without accounting for non-linearity of economic effects, or where on the non-linear trajectory lies each individual herd. Our research proposes new approaches for environment-customized genetic selection as a tool to further enhance livestock performance, specially under environments that are less favorable for animal production systems. Using a proof-of-concept simulation study on two antagonistic traits representing a production and fertility trait in dairy cattle, we examined the medium to long-term impact of tailoring selection to specific environments, in terms of genetic progress. A key question is the trade-off between having a single or few accepted breeding indexes, which are often used for trading purposes, versus each herd having a bespoke index. Results of the simulation study suggested that environment-customized selection can increase the genetic progress of fertility by up to 70% compared to traditional selection, without significantly compromising the genetic progress for production.

Keywords: 2026

How to Cite:

Bedère, N., Berry, D., C. D. Cuyabano, B., Friggens, N., Lassen, J., Martin, P., Miglior, F. & Stephansen, R., (2026) “New approaches for environment-customized genetic selection”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286442. doi: https://doi.org/10.31274/wcgalp.24007

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