EFFECT OF DYSTOCIA ON YIELD, FERTILITY, AND COW LOSSES AND AN ECONOMIC-EVALUATION OF DYSTOCIA SCORES FOR HOLSTEINS

Lactation records of US Holstein cows were analyzed with mixed models to determine the effect of dystocia on 305-d milk, fat, and protein yi elds, days open, number of services, and cow losses and to estimate th e economic loss associated with dystocia. The data were 122,715 record s of 71,618 cows from 1980 to 1991. The single-trait animal model incl uded herd-year-season, sex of calf, age of dam, and dystocia score as fixed effects and animal and permanent environment as random effects. The effect of dystocia was significant (P < 0.01) on all traits within and across parities. Over multiple parities, the differences between score 5 (extreme difficulty) versus score 1 (no problem) for milk yiel d, fat yield, protein yield, days open, number of services, and cow de aths were 703.6 kg, 24.1 kg, 20.8 kg, 33 d, 0.2 services, and 4.1%, re spectively. The losses associated with traits were priced and summed t o determine the total economic loss associated with dystocia. In addit ion, calf mortality was considered to be a cost. Across parities, esti mates of costs were $0.00, $50.45, $96.48, $159.82, and $379.61 for sc ores 1 to 5, respectively. Cost of dystocia was relatively higher on a per incidence basis than would be expected from the mean of the popul ation. The total cost associated with dystocia (i. e., within-parity s um of costs associated with dystocia scores weighted by the probabilit y of occurrence) was $28.53 for an average heifer and about $10.00 for an average cow for other parities.