GxE

The importance of trait stability in crossbreeding: uncovering the impacts of genotype-by-environment interaction

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Abstract

Intensive dairy farming maximises milk production under optimised conditions. In tropical systems, however, optimal conditions are often unavailable. Challenges such as heat stress, resource variability, and climate unpredictability limit response to selection and delay genetic progress. Crossbreeding high-performing exotic breeds with locally adapted breeds is a common strategy to improve tropical dairy. In practice, responses to crossbreeding are highly variable, which can be attributed to a primary focus on mean performance while often overlooking genotype by environment interaction (GEI). Despite evidence of substantial dissimilarity between temperate and tropical environments, few quantitative approaches have been developed to address the impact on crossbred performance. In this talk, we introduce a framework for exploring and utilising GEI to inform crossbreeding strategies in tropical systems, thereby improving the performance and stability of crossbred performance. Using stochastic simulations, we compare three breeding programmes: a purebred temperate programme with a taurine breed, a purebred tropical programme with an indicine breed, and a tropical crossbreeding programme. We assume a multi-trait model with different environments simulated as different traits. The temperate programme operates in a favourable environment, E1, with intense selection based on performance in that environment only. The tropical purebred and crossbred programmes operate across five environments, E2-E6, representing a gradient of tropical conditions that deteriorate towards E6. Selection is based on the average performance across E2-E6. GEI is generated by varying the correlation between environments, with a strong correlation of 0.9 between neighbouring environments, e.g. E1 and E2, followed by a decrease of 0.3 for subsequent pairs. A negative correlation of -0.3 is observed for the most distant pairs (E1 and E6). We demonstrate that ignoring GEI during selection increases genetic variability across tropical environments, reflecting a decrease in trait stability, as the temperate germplasm is not adapted to tropical environments. This motivates the strategic use of temperate germplasm for optimising tropical crossbreeding . To this end, we develop a framework that disentangles non-crossover and crossover components of GEI in terms of response to selection and adaptation potential to a set of focal environments. Given the intensive selection of bulls in the temperate environment, we initially focus on E1 and examine the correlated response to selection in tropical environments E2-E6. We then examine the adaptation potential of these bulls through their environmental sensitivity to identify the best candidates for crossbreeding. Our work provides important insights to understand the impacts of GEI on tropical dairy and offers novel framework for optimising crossbreeding programmes. By identifying and matching parents with complementary adaptation patterns, farmers can produce high-performing stable crosses. Overall, we aim to reframe GEI from a breeding constraint into a useful source of variation for informing breeding decisions, thereby supporting the sustainable future of tropical dairy farming.

Keywords: 2026

How to Cite:

Gorjanc, G., Mafra Fortuna, G., Tolhurst, D. & Waters, D., (2026) “The importance of trait stability in crossbreeding: uncovering the impacts of genotype-by-environment interaction”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285805. doi: https://doi.org/10.31274/wcgalp.23798

Rights: 1