K.L. Parker Gaddis*1, P.M.VanRaden†, J.B. Cole†, H.D. Norman*, E. Niccolzai*, and J.W. Durr*
*Council on Dairy Cattle Breeding, Bowie, MD 20716
†Animal Genomics and Improvement Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350
1Corresponding author
2019 J. Dairy Sci. (?)
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The rate at which new traits are being developed is increasing, leading to an expanding number of evaluations provided to dairy producers, especially for functional traits. This review will discuss the development and implementation of genetic evaluations for direct health traits in the U.S., as well as potential future developments. Beginning in April 2018, routine official genomic evaluations for six direct health traits in Holsteins were made available to U.S. producers from the Council on Dairy Cattle Breeding (Bowie, MD). Traits include resistance to milk fever, displaced abomasum, ketosis, mastitis, metritis, and retained placenta. These health traits were included in net merit indices beginning in August 2018 with a total weight of approximately 2%. Previously, improvement of cow health was primarily made through changes to management practices or genetic selection on indicator traits, such as somatic cell score (SCS), productive life, or livability. Widespread genomic testing now allows for improvement of traits with low heritabilities such as health; however, phenotypes remain essential to the success of genomic evaluations. Establishment and maintenance of data pipelines is a critical component of health trait evaluations, as well as appropriate data quality control standards. Data standardization is a necessary process when multiple data sources are involved. Model refinement continues, including implementation of variance adjustments beginning with the April 2019 evaluation. Mastitis evaluations are submitted to Interbull along with SCS for international validation and evaluation of udder health. Additional areas of research include evaluation of other breeds for direct health traits, use of multiple-trait models, and evaluations for additional functional traits such as calf health and feed efficiency. Future developments will require new and continued cooperation among numerous industry stakeholders. There is more information available than ever before with which to make better selection decisions; however, this also makes it increasingly important to provide accurate and unbiased information.
Key Words: genetic parameter, genomic evaluation, health trait