320 Genomic Predictions for Calf Wellness in Holstein Cattle.

Abstract

Reducing calf morbidity and mortality is important for attaining financial sustainability and improving animal welfare on commercial dairy operations. Zoetis has developed genomic predictions for calf wellness traits in Holsteins that include Calf Livability (recorded between 2 and 365 days of age), Calf Respiratory Disease (recorded between 0 and 365 days of age), and Calf Scours (recorded between 2 and 50 days of age). Phenotype and pedigree data were obtained from about 300 commercial dairies. The number of records ranged from 726,129 for Scours to 1,874,587 for Livability. The number of genotyped animals was approximately 500,000. The analyses were performed using the single-step genomic BLUP method under univariate threshold animal model containing the fixed effect of year of birth x season x region and the random effects of herd x year of birth and animal. Estimated heritabilities were 6.0%, 4.2%, and 4.5% for Livability, Respiratory Disease, and Scours, respectively. The solutions were expressed as standardized transmitting abilities (STA) with a mean of 100 and a standard deviation of 5. An animal with a higher STA has a lower relative disease risk than an animal with a lower STA. The STAs ranged between 66 and 115, 83 and 116, and 84 to 117 for Livability, Respiratory Disease, and Scours, respectively. The average reliabilities for genotyped animals without own phenotype were 44%, 39%, and 40% for Livability, Respiratory Disease, and Scours, respectively. The results indicate that a direct evaluation of calf wellness traits under a genomic threshold model is feasible and offers predictions with average reliabilities comparable to other lowly heritable traits. When coupled with sound management practices, genetic selection for calf wellness traits presents a compelling opportunity for dairy producers to help manage herd replacement costs and improve overall profitability.