GxE

Assessing genotype-by-environment interactions across climatic conditions for feeding behavior traits and dry matter intake in tropical beef cattle

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Abstract

Rising global temperatures have intensified heat stress in beef cattle, especially in tropical regions, leading to reduced feed intake, behavioral changes, and higher maintenance requirements that compromise animal productivity and welfare. Therefore, the main objective of this study was to investigate genotype-by-environment interactions (Gà—E) for feeding behavior traits and dry matter intake (DMI) in Nellore cattle using reaction norm models with the Temperature-Humidity Index (THI) as the environmental gradient descriptor. We analyzed 5,106 animals from 44 feed-efficiency trials, totaling 317,249 records per trait for number of feeding events per day (FEn), duration per feeding event (FEd, min/visit), interval between feeding events (TBfe, min), total feeding time per day (FTd, min/day), feeding rate (FR, g/s), and DMI (kg DM/day). Meteorological information was retrieved from NASA POWER and daily THI was computed based on mean daily values of temperature and relative humidity recorded during the trials. Additive genetic and permanent environmental (co)variances were estimated using the Best Linear Unbiased Prediction approach (BLUP) modeled with Legendre orthogonal polynomials on THI, allowing the estimation of THI-specific heritabilities and genetic correlations between environmental levels. Model fit was compared under homogeneous and heterogeneous residual variance structures, and the heterogeneous models consistently showed superior goodness of fit. The genetic expression of feeding behavior traits and DMI was modulated by climatic conditions, with heritability estimates varying across the THI gradient for all traits: FEn (0.13 to 0.28), FEd (0.12 to 0.24), TBfe (0.04 to 0.15), FTd (0.14 to 0.23), FR (0.13 to 0.16), and DMI (0.07 to 0.18). For FEn, FEd, TBfe, FTd, and DMI, the highest heritability estimates were observed under more favorable conditions (lower to intermediate THI values), whereas FR showed comparatively limited variation across THI levels. The lowest genetic correlations were observed between the most contrasting conditions (THI 53 vs 80), with values of −0.08 for FEn, 0.10 for FEd, 0.12 for TBfe, 0.44 for FTd, 0.55 for FR, and −0.28 for DMI, indicating meaningful Gà—E and potential re-ranking of animals under contrasting climatic conditions. Moreover, genetic correlations between DMI and feeding behavior traits were also THI-dependent, ranging from 0.31 to 0.69 with FEn, from -0.32 to 0.22 with FEd, from -0.28 to 0.15 with FR, from 0.48 to 0.51 with FTd, and from -0.57 to -0.34 with TBfe, highlighting shifts in the genetic architecture of feed intake under different THI levels. In conclusion, these results demonstrate that feeding behavior-related traits in tropical beef cattle are sensitive to climatic conditions, that ignoring Gà—E may bias selection toward animals adapted only to intermediate THI, and that incorporating reaction norm parameters into breeding objectives is a feasible strategy to improve climatic resilience in tropical production systems.

Keywords: 2026

How to Cite:

Silva Neto, J., Baldi, F., Mota, L., Rodrigues, G., Mendes, E., Sainz, R., Valente, J. & Brito, L., (2026) “Assessing genotype-by-environment interactions across climatic conditions for feeding behavior traits and dry matter intake in tropical beef cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286620. doi: https://doi.org/10.31274/wcgalp.24070

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