Genetic analysis of resilience in Israeli Holstein cattle based on first parity daily rumination and milk production records.

Resilience in farm animals was proposed as an indicator trait for health and robustness. One approach is to analyze the variance and autocorrelation of daily milk production. Daily rumination time is a useful indicator of health status. Recently developed rumination monitoring tags provide accurate daily output data on large numbers of cows. Genetic correlations were computed between the means, log variances, and autocorrelations of daily milk production and rumination time, 5 metabolic diseases (retained placenta, metritis, ketosis, displaced abomasum, and milk fever), 7 traits included in the Israeli selection index, and BCS near calving. The first 40 DIM and the remainder of the lactation of 40,860 first-parity cows calving between 2019 and 2024 were analyzed separately. Significant genetic correlations of the resilience indicator traits were found for all 5 diseases, BCS, and all 7 index traits. The log variance of daily milk production during the first 40 DIM had a heritability of 0.11 and was the best resilience indicator among those tested. A correlation of -0.62 was found between this trait and ketosis incidence. Coefficients of determination for the breeding values for the Israeli breeding index based on 7 indicator traits computed from 1 to 40 DIM were 0.18 for cows and 0.19 for sires. Inclusion of a resilience predictor trait based on the first 40 DIM in the selection index is justified to improve selection decisions for young cows and sires.