Disease & heat resistance

Genetic evaluation of dairy cattle resilience using perturbations in daily milk yields

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Abstract

Fluctuations in milk yield offer insights into disturbances that occur throughout the lactation period of dairy cows. Identifying the underlying causes of these perturbations and understanding the responses of cows, however, remains a complex challenge. Various factors, such as the onset of disease or exposure to extreme temperatures, can contribute to these perturbations, making it difficult to disentangle their effects. Additionally, some of these disturbances may not have been well-defined, hence they may go unnoticed. Preferably, cows that are minimally affected by such disturbances or that quickly recover to their baseline performance are highly desirable. The availability of daily milk yield records from automatic milking systems in the Austrian dairy system presents an opportunity to investigate genetic differences among cows during periods of perturbation. Our dataset consisted of 37,118 Fleckvieh cows from up to 6 parities, for which individual lactation curves were modelled using the Wilmink function. Perturbations were identified as consecutive herd-milking days when the mean observed milk yield was at least 3% below the expected mean milk yield. Our study was modelled on the basis that events occurring on specified days or periods will affect most, if not all, cows in a herd during the period of stress. Perturbations were categorized into groups based on the duration of perturbations and the severity of the deviation between the mean observed and the mean expected milk yields. The severity levels ranged from ≥3% to ≥7%, while the duration ranged from ≥3 to ≥10 days. Using these perturbations, cow-level responses were analysed by defining our resilience indicator, ΔMY, which is the percentage change in a cow's daily mean milk yield relative to expected during the perturbation period. This study assumes no missing or overlapping perturbation events for simplicity in modelling. Variance components were estimated and heritabilities calculated for different combinations of perturbation duration and severity of the percentage difference between observed and expected mean milk yields using the univariate animal model. Fixed effects included age at first calving combined with parity class and days in milk at perturbation onset, while random effects comprised additive genetics and permanent environment. Heritability for ΔMY was generally low, ranging from 0.00 (0.00) to 0.13 (0.03), and increased with an increase in the severity of the percent deviation in milk yields and perturbation duration. The findings from this study indicate that animals within herds exhibit varying responses to disturbances compared to their herd mates.

Keywords: 2026

How to Cite:

Agyiri, M., Onzima, R., Costa, A., Fuerst-Waltl, B., Gruber, S., Himmelbauer, J., Steininger, F., Egger-Danner, C., Mészáros, G. & Sölkner, J., (2026) “Genetic evaluation of dairy cattle resilience using perturbations in daily milk yields”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2283857. doi: https://doi.org/10.31274/wcgalp.23528

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