Genetic Studies on Disease Recordings in First Lactation Cows of Swedish Dairy Breeds

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Abstract
Records on veterinary treatments of 11,797 1st-lactation cows sired by 50 Swedish Red and White (SRB) and 34 Swedish Friesian (SLB) AI [artificial insemination] bulls were analyzed; 22.9 and 28.7% of SRB and SLB cows, respectively, were treated. Udder problems were the most frequent disease for both breeds, though more frequent in SLB. Differences among herds were the most important source of variation, amounting to 9% (at most) of total variation. Overall, the additive genetic variation was 2-3 times less than herd variation. Significant effects of year, month and age at calving were found for several diseases. Differences between daughter groups were significant for teat injuries, mastitis, teat or udder disease, foot, leg, or locomotory diseases, veterinary treatments whatever the origin, and culling rate in SRB breed. Only teat injuries, foot, leg or locomotory diseases, and veterinary treatments whatever the origin were significant in SLB breed. Heritability estimates varied between zero and 4.6%. The highest value was obtained for udder or teat diseases in SRB. A difference of 10% in transmitting ability for veterinary-treated daughters in 1st lactation existed between extreme bulls within each breed, despite the small number of bulls exceeding 100 daughters which was chosen as a minimum. For a more thorough evaluation of selection for disease resistance, analyses should be done on data that include more than 1 lactation, when production records should be related to incidence of diseases. Disease frequency should be taken into account together with other traits in the selection of bull sires, provided progeny tests can be obtained on sufficiently large daughter groups.