Characteristics and management practices associated with milk production in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association programs

Objective To determine herd characteristics and management practices associ ated with milk production in dairy herds enrolled in official Dairy Herd Im provement Association (DHIA) programs in Ohio. Sample Population-186 dairy farms in Ohio. Procedure-All herds in official DHIA programs in 9 counties were invited to participate. Information regarding herd characteristics and management pra ctices was obtained, using a standardized questionnaire. Bulk-tank milk sam ples were obtained for bacteriologic culture. Official DHIA test-day record s were obtained, and associations were identified, using multivariable ANOV A procedures. Results-Of 479 eligible producers, 186 (39%) participated, and consecutive bulk-tank milk samples were available for culture from 172 (36%). Streptoco ccus agalactiae and Mycoplasma spp were not recovered from bulk-tank milk s amples, but Staphylococcus aureus was recovered from 64 (37%) herds. Mean ( +/- SD) number of lactating cows in participating herds was 97 +/- 66, with 123 (66%) herds milking < 100 cows. The RHA was significantly associated w ith number of cows in milk, estimated percentage of herd detected in estrus , reported annual percentage of heifer calves born alive that died before 8 weeks old, percentage days in milk, use of bovine somatotropin during the preceding 2 years, and sex of the person completing the questionnaire. Conclusions and Clinical Relevance In this study, the strongest indicator o f milk production was number of cows in milk. However, merely adding cows t o a herd should not be considered to guarantee increased milk production, b ecause other management traits could be confounded with increased number of cows in a herd.