Compliance with recommended drug withdrawal requirements for dairy cows sent to market in Michigan.

By examination of computerized individual cow records from January 1981 through June 1985, compliance with premarketing drug withdrawal times was investigated in 23 dairy herds. During this period, 877 cows were culled from 23 herds; 33 cows from 12 herds were in violation of premarketing drug withdrawal times. Six herds had 1 violation, 2 herds had 2 violations, 2 herds had 3 and 4 violations, and 2 herds had 7 and 9 violations. Fifty drugs had been used; 15 drugs were used in violation of drug withdrawal times before cows were sent to market. The most commonly used drugs in violation were oxytetracycline, gentamicin, chloramphenicol, and a combination of lincomycin/spectinomycin. Significant differences between cows in violation and cows not in violation were not observed for age, lactation number, milk production, herd size, or month of culling. However, the 12 herds in violation of premarket drug withdrawal times had significantly (P less than 0.05) more cows culled within 30 days for retained placenta and milk fever, and more cows culled within 30 and 100 days for mastitis, metritis, and displaced abomasum. Although not significant, the 2 herds with 7 and 9 violations had more hired vs family labor than did the other herds with violations.