Correlated Responses of Health Cost to Selection for Milk Yield in Jerseys

Abstract

Health data were analyzed for 567 Jersey cows resulting from direct selection for milk yield and 193 cows in a control line. Controls were daughters of bulls selected randomly from commercial AI sampling programs in 1967. Health costs were expenses due to drugs, labor, and veterinary charges. Health expenditures were for mammary care, locomotion, respiration, reproduction, digestion, and other. Costs were summed across lactation for each cow and discounted back to year of birth at a rate of 3%. The linear model included effects of year-season of freshening, parity, line, sire within line, and lactation length. Selection cows had significantly higher health costs, and the differences between lines were mainly due to higher costs for mammary care. Differences between lines for individual categories were not significant but tended to be higher for selection cows. Parity, year and season, and stage of lactation were important nongenetic sources of variation for health costs. Costs were greatest for third and later parities, and during the first 30 d of lactation for all cows. Results indicate that health costs increased with selection for milk yield. More intensive management of cows in early lactation and later parities may decrease health expense. © 1990, American Dairy Science Association. All rights reserved.