Reliability of genomic breeding values for health traits in Holstein dairy cows
The article deals with the reliability of udder breeding values and the foot and claw disorders in Holstein cattle. Breeding values and their reliability have been estimated for clinical mastitis, foot and claw infection diseases, non-infectious foot and claw disorders, foot and claw disorders, including lameness, and foot and claw disorders and lameness alone. A single- trait linear animal model with repeatability was used for evaluation. The most extensive dataset of 97,674 cows was used to estimate breeding values for foot and claw diseases, including lameness. The smallest dataset of 21,552 cows was used for non-infectious foot and claw disorders. A single-step genomic estimation method was used to estimate genomic breeding values. The reference population was in the range of 25,458 animals, bulls 5,107, cows and heifers 20 351. The final number of SNPs was 35,934. The lactation incidence was highest in clinical mastitis at 23.55 %, the lowest in lameness at 10.61 %. Heritabilities were in the range of 3.13 % for lameness and 5.48 % for infectious foot and claw diseases. The genomic evaluation positively increased the reliability of breeding values in genotyped individuals by 11 pp to 12 pp. If there is another factor at play to improve reliability, its effect may exceed the genotyped animal’s genomic estimation effect. In bulls, sires with daughters in datasets, there was a lower increase in reliability than for genomic cows and heifers (increase from 12 pp to 13 pp), on average only by 8 pp. In conclusion, the use of genomic selection is essential to improve reliability in young animals.
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