Disease & heat resistance
Authors: Fiona Louise Guinan (Council on Dairy Cattle Breeding) , John B. Cole (Council on Dairy Cattle Breeding) , Robert Fourdraine (Dairy Records Management Systems) , Francisco Peñagaricano (University of Wisconsin–Madison) , Kent Weigel (University of Wisconsin–Madison)
This work assesses different approaches to quantifying resilience in U.S. dairy cattle using high-frequency data, specifically daily milk weights. Our dataset contained 62,580,945 daily milk weights and pen locations of 227,633 Holstein cows in parity 1, 2, or 3 across 204 herds in 30 U.S. states. We first evaluated consistency, defined as the ability to perform as expected each day of lactation. Temporal variance (TEMPVAR) of milk yield from 5 to 305d postpartum was computed as the log-transformed variance of daily deviations between observed and expected individual milk weights, where lower values of TEMPVAR indicate consistent performance. Expected milk weights were estimated using LOESS (span = 0.75) and polynomial quantile regression (quantiles = 0.5, 0.7). TEMPVAR heritabilities (standard errors) ranged from 0.23(0.01) to 0.24(0.01). Genetic correlations between TEMPVAR and fitness traits, including longevity and health, indicate that more consistent cows tend to have fewer health problems and greater longevity. We then evaluated resilience, defined as cow's capacity to recover after a disturbance or maintain specific functions under stress. Note that resilience is a multifaceted trait expressed after a perturbation occurs. The first challenge is detecting the disturbance; the second is quantifying the cow's response to that disturbance. We developed a data-driven approach to identify perturbations using pen level expected and observed performance. Forty combinations of perturbation severity (≥3% to ≥7% milk yield loss) and duration (≥3d to ≥10d) were evaluated to estimate variance components and genetic parameters. Our resilience phenotype, delta milk yield (𝚫MY), measures the change in a cow's mean daily milk yield relative to her expected yield during a perturbation. Heritability estimates for 𝚫MY ranged from 0.01(0.00) to 0.20(0.08), increasing with perturbation severity and duration. Genetic correlations between 𝚫MY and TEMPVAR ranged from -0.51(0.01) to -0.16(0.03), indicating that consistency and resilience are correlated but different traits. Furthermore, for one subset of perturbations (≥5% severity and ≥5d duration), we evaluated seven alternative resilience phenotypes describing response and recovery. The first consisted of 4 resilience phenotypes calculated using change in milk yield (𝚫MY) over numerous days relative to the pen nadir. These include (1) 𝚫MY throughout the entire event, (2) 𝚫MY before the nadir, (3) 𝚫MY near the nadir, and (4) 𝚫MY after the nadir. The second group of resilience phenotypes were calculated using a single day during the perturbation and include (5) residual on d1 of the perturbation, (6) residual at the nadir, and (7) residual on the last day of the perturbation. Heritability estimates ranged from 0.004 (0.004) to 0.04 (0.009) for resilience phenotypes. Genetic correlations with 305-d milk yield ranged from −0.02 (0.45) to −0.30 (0.38), suggesting resilience can be improved while maintaining milk production. Overall, both consistency and resilience were heritable and favorably correlated with fitness traits.
Keywords: 2026
How to Cite: Guinan, F. , Cole, J. , Fourdraine, R. , Peñagaricano, F. & Weigel, K. (2026) “Genetics of dairy cow resilience in US Holsteins”, World Congress on Genetics Applied to Livestock Production Digital Archive. 2026(1). doi: https://doi.org/10.31274/wcgalp.23390