|PARKER GADDIS, KRISTEN - Council On Dairy Cattle Breeding|
|MEGONIGAL, JOEL - Council On Dairy Cattle Breeding|
|CLAY, JOHN - Dairy Records Management Systems(DRMS)|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2017
Publication Date: 6/24/2017
Citation: Parker Gaddis, K.L., Tooker, M.E., Wright, J.R., Megonigal, J., Clay, J.S., Cole, J.B., Van Raden, P.M. 2017. Development of genomic evaluations for direct measures of health in U.S. Holsteins and their correlations with fitness traits. Journal of Dairy Science. 100(Suppl. 2):378(abstr. 377).
Technical Abstract: The objectives of this research were to estimate variance components for 6 common health events recorded by producers on U.S. dairy farms, as well as investigate correlations with fitness traits currently used for selection. Producer-recorded health event data were available from Dairy Records Management Systems (NCSU, Raleigh, NC) for 6 common health events occurring in U.S. dairy herds: hypocalcemia (CALC), displaced abomasum (DSAB), ketosis (KETO), mastitis (MAST), metritis (METR), and retained placenta (RETP). Standardization and editing constraints were applied to ensure data validity. After editing, number of phenotypic records ranged from 1.2 million for CALC up to 2.5 million for MAST. Traditional PTA were calculated for 63.1 million Holsteins using a linear animal model accounting for year-season, age-parity, herd-year, permanent environmental effects, as well as a regression on inbreeding. Heritability estimates were 0.6%, 1.1%, 1.2%, 3.1%, 1.4%, and 1.0% for CALC, DSAB, KETO, MAST, METR, and RETP, respectively. Genomic PTAs were calculated using 60,671 markers for 1.36 million Holsteins. For bulls with > 90% reliability (or > 75% for CALC and RETP), health trait PTAs had low correlations with PTA protein (-0.03 to 0.23) but much higher correlations with official PTAs for several fitness traits included in net merit. Largest correlations for each health trait were -0.68 for MAST with somatic cell score (SCS), 0.59 for KETO with daughter pregnancy rate (DPR), 0.47 for DSAB with livability, 0.46 for METR with DPR, -0.29 for CALC with SCS, and 0.17 for RETP with productive life (PL). An economically weighted sum of all 6 health trait PTAs was correlated by 0.56 with PL, 0.55 with livability, 0.50 with DPR, and -0.45 with SCS, using estimated costs per case of $72 for MAST, $178 for DSAB, $105 for METR, $64 for RETP, $38 for CALC, and $28 for KETO. Young animal reliabilities averaged 11-18% from the pedigree model vs. 40-49% from genomic predictions. The SD of lifetime net merit is $193 compared to $8 for the sum of health trait PTAs that could be included in the near future.