Antimicrobial treatment of clinical mastitis in the eastern United States: The influence of dairy farmers' mastitis management and treatment behavior and attitudes.

To assess both the behaviors and social variables related to antimicrobial therapy for clinical mastitis, we sent a survey to 1,700 dairy farms in Michigan, Pennsylvania, and Florida in January and February 2013. The survey included questions related to 7 major areas: sociodemographic and farm characteristics, milking proficiency, milking systems, cow environment, infected cow monitoring and treatment, farm labor, and attitudes toward mastitis and related antimicrobial use. The overall response rate was 41% (21% in Florida, 39% in Michigan, and 45% in Pennsylvania). Herd size ranged from 9 to 5,800 cows. Only a small proportion of herds frequently or always cultured milk samples for bacteriology from cows with a high somatic cell count (17%), cows with clinical mastitis (18%), or bulk tank milk (13%). Likewise, only 56% of herds frequently or always maintained records of all treated cows and 49% reviewed records before administering mastitis treatments. Multivariate analysis determined that use of treatment records was associated with increased likelihood of frequent use for both intramammary (IMA) and systemic (SYA) administration of antimicrobial drugs for therapy of clinical mastitis. As would be expected, use of natural (organic) therapies was associated with decreased use of IMA, as was the respondent being a member of an Amish community. Lower levels of education and the use of bacterins to control Staphylococcus aureus mastitis were also associated with decreased IMA, whereas increased use of IMA at dry off and the belief that "bad luck" plays a role in mastitis problems were associated with increased IMA. Use of an internal teat sealant, the respondent being the sole proprietor, being from Michigan, use of conductivity to measure subclinical mastitis, the respondent placing increasing importance on decreasing antibiotic residues in cull cows, and having financial incentives for employees linked to somatic cell count were associated with increased use of SYA for the treatment of clinical mastitis. Use of sand or mattresses for bedding were associated with decreased SYA. These findings highlight the need to improve the acceptance of practices that are consistent with prudent antimicrobial use for the treatment of clinical mastitis on dairy farms. Additionally, the willingness of dairy farmers to administer antimicrobial drugs for the treatment of clinical mastitis is associated with other mastitis-related practices and attitudes. The Authors. Published by the Federation of Animal Science Societies and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).