Abstract

The objectives of this research were to develop and implement genetic and genomic evaluations for resistance to six common health events reported in U.S. dairy herds. Events included hypocalcemia (milk fever), displaced abomasum, ketosis, mastitis, metritis, and retained placenta. Dairy Records Management Systems (Raleigh, NC) provided producer-recorded data for these six health events. After applying standardization and editing constraints to the data, there were 3.1 million records from 1.7 million Holsteins. Variance components were estimated for each trait using univariate linear animal models. Heritability estimates on the observed scale were 0.6%, 1.1%, 1.2%, 3.1%, 1.4%, and 1.0% for hypocalcemia, displaced abomasum, ketosis, mastitis, metritis, and retained placenta, respectively. Traditional predicted transmitting abilities (PTA) were calculated for 63.1 million Holsteins through pedigree relationships using a linear animal model including effects of year-season, age-parity, herd-year, and permanent environment, as well as a regression on inbreeding. Genomic PTA were calculated using 60,671 markers for 1.36 million Holsteins. Young animal reliabilities averaged 11-18% in the pedigree-based model versus 40-49% using genomic information. Average reliabilities for proven animals ranged from 20-33% in the pedigree-based model compared to 44-56% from genomic predictions. Health trait PTA were correlated with several traits included in the Net Merit index (NM$). Estimated cost per case for each health event was estimated using recent calculations of direct costs in literature, while also accounting for adjustments traditionally made for abnormal test-day records. Direct costs for each health event ranged from $28 for ketosis up to $197 for displaced abomasum. The six health traits together will receive 2-3% of the total relative emphasis when included in NM$. Keywords: dairy, economic, genomic evaluation, health trait

Kristen Parker Gaddis, Melvin Tooker, Janice Wright, Joel Megonigal, John Clay, John Cole, Paul VanRaden

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Genetic gain - Breeding Objectives and Economics of Selection Schemes 1, , 594, 2018
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