Six health traits will be incorporated into the Net Merit Index of Holstein sire evaluations this August. The traits include hypocalcemia, displaced abomasa, ketosis, mastitis, metritis and retained placentas.
The traits were originally scheduled to be included in Net Merit in the April sire run. But inclusion was delayed as technical issues were sorted out. More breeds will be added as more information for each breed is accumulated.
The evaluations for individual Council on Dairy Cattle Breeding (CDCB) disease resistance traits will be incorporated into Net Merit at levels that appropriately reflect their economic value as demonstrated through sound science, say Kristen Gaddis, a CDCB geneticist.
The health traits are correlated to other traits already in the index, such as productive life and livability. CDCB and USDA geneticists have taken these correlations into account so that the traits aren’t double counted, explains Gaddis.
The heritability of each trait is low: Hypocalcemia, 0.6%; DAs, 1.1%; ketosis, 1.2%, mastitis, 3.1%; metritis, 1.4%, and RPs, 1%. Nevertheless, genetic resistance to the traits is additive and permanent, so over time and over generations, disease resistance can be built up and accumulated