Disease & heat resistance

Genetic heterogeneity of residual variance of 305-day milk yield as a resilience indicator in Spanish Holstein dairy cows: a first approach

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Abstract

This study represents an initial approach to evaluating the potential use of the residual variance of 305-day milk yield as an indicator of resilience in the Spanish Holstein population. Resilience in dairy cows refers to their ability to maintain production and recover quickly after environmental or physiological disturbances. Identifying resilient animals is essential for improving herd robustness and sustainability under variable management and climatic conditions. The 305‑day milk yield is routinely recorded in official milk recording systems and reflects a cow's capacity to sustain production throughout lactation. Statistical analyses were performed using the GSEVM program, which can jointly estimate parameters for the mean trait and its environmental variance. The double hierarchical generalized linear model assumed that both the mean 305-days milk yield and its residual variance (the resilience indicator trait) were affected by systematic and random effects, with the environmental variance heterogeneous and partially under genetic control. Systematic effects included herd-year of calving (119 levels), calving month (12 levels), and lactation-age at calving (44 levels). Animal (with a pedigree-based relationship matrix including 163,361 individuals) and permanent environmental effects were considered random. The final dataset included 75,078 lactations from first to fifth parity, recorded between 2021 and 2024, from 32,121 Holstein cows across 42 herds. The estimated genetic variance of the residual variance of 305-day milk yield (and its posterior standard deviation) was 0.40 (0.04) and the genetic coefficient of variation for residual variance was 0.64. The genetic correlation between the mean and the residual variance was moderate to high of -0.67 (0.02), suggesting that higher-producing cows tended to be less affected by environmental perturbations, since the lactation-age group included in the model may be adjusting for the structural effect of milk yield. In this first study addressing resilience indicators in the Spanish Holstein population, the residual variance of 305-day milk yield showed sufficient genetic variability and favorable correlations with milk yield, supporting its use as a practical proxy for resilience in dairy cattle. However, these results contrast with some previous reports in literature and further research is needed.

Keywords: 2026

How to Cite:

Cervantes, I., Garcà­a-Garcà­a, D., Gutiérrez, J., Jiménez-Montero, J. & Pérez-Cabal, M., (2026) “Genetic heterogeneity of residual variance of 305-day milk yield as a resilience indicator in Spanish Holstein dairy cows: a first approach”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285431. doi: https://doi.org/10.31274/wcgalp.23703

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