Genomic Evaluation for Calf Health in Canada
Abstract
A genomic evaluation for calf health traits was developed for the Holstein breed in Canada effective August 2025. The new Calf Health index aims to increase resistance to the two most prevalent calf diseases on Canadian farms, respiratory problems (RESP) and diarrhea (DIAR). Producer-recorded respiratory problems and diarrhea health events recorded in the first 180d and 60d, respectively, of a heifer calf’s life, are used in the genetic evaluation. RESP and DIAR, coded as binary traits, are used in a two-trait linear animal model considering a fixed year-season effect and random herd-year-season, animal, and residual effects for both traits. Genetic parameters were estimated by the MC EM REML method using 310 662 calf records from 1 179 herds. Heritability estimates were 0.05 for RESP and 0.04 for DIAR, with a genetic correlation of 0.53 between the traits. A Single-step genomic evaluation was implemented using the MiX99 software. A June 2025 evaluation test run had 355 355 records for RESP and 144 495 for DIAR, collected from 1 442 Canadian herds from 2007 to 2025. There were 74 013 calves with health records that were genotyped and a total of 119 715 genotyped animals in the reference population. The overall prevalence for RESP and DIAR was 19.5% and 21.1%, respectively. The Calf Health index combines genomic estimated breeding values for RESP and DIAR at equal weightings. Calf Health evaluations are published as a relative breeding value, with a mean of 100 and standard deviation of 5 for base bulls, where higher values represent greater resistance to calf health diseases. No genetic trend was observed and only weak relationships with other routinely evaluated traits were present. From a sire comparison analysis, clear differences were found when comparing high and low RBV sires in terms of daughter disease rates, highlighting the potential of the evaluation. Genetic selection for improved calf health is a valuable tool for animal welfare, lifetime animal production, and overall herd profitability.
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