Improved genetic evaluation of health traits using metabolic biomarkers in Nordic dairy cattle
Keywords:
Genetic evaluation, Health, Metabolic biomarkers, Animal model, Nordic Dairy Cattle, breeding values.Abstract
In 2008, a joint Nordic genetic evaluation for health traits was developed for Denmark, Finland and Sweden. The sire model used up until 2017 for routine evaluation utilized records on veterinary treatments to provide breeding values for Reproductive Disorders, Metabolic Disorders, and Feet&Leg Problems. Today, with the accessibility of metabolic biomarkers (β-hydroxybutyrate (BHB) and Acetone) and with genomic prediction models prepared to include cows in the reference population, the addition of valuable indicator traits and the use of an animal model is a more optimal solution for the General Health (GH) evaluation.
In November 2017, the GH evaluation changed from having four sub-traits to five sub-traits. The four sub-traits were: Early and Late reproductive disorders, Feet and Leg problems and Metabolic disorders. In the new GH evaluation the later was split into Ketosis and Other Metabolic Disorders. This was motivated by the inclusion of BHB and Acetone, with the purpose of exploiting the high genetic correlations between Ketosis and BHB (~ 0.68) and Ketosis and Acetone (~ 0.78). Heritability estimates were significantly higher for BHB (h2 = 0.15) and Acetone (h2 = 0.06) compared to Ketosis (h2 = 0.012) and Other Metabolic Disorders (h2 = 0.006) in first lactation records for Holstein. This new information helped improving the reliability of breeding values for Ketosis and Other Metabolic disorders, from 0.29 to 0.34 and 0.36 for Other Metabolic Disorders and Ketosis, respectively in Holstein cows.
The new overall GH index is composed of five sub-traits: Early and Late Reproductive Disorders, Ketosis, Other Metabolic Disorders, and Feet&Leg Problems. Each of them is weighted according to a set of economical values. The improvements introduced to the GH evaluation affected the breeding values of the GH index considerably. For progeny tested AI bulls born after 2009 and with a reliability for GH index > 0.35 the correlations between the old and the new GH index, were 0.89 for RDC and 0.92 for HOL.
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