USDA Releases Report on Antimicrobial Use on U.S. Dairies

Veterinary Services

October 14 , 2005

The U.S. Department of Agriculture's National Animal Health Monitoring System (NAHMS) has released a descriptive report entitled Part IV: Antimicrobial Use on U.S. Dairy Operations, 2002. The report was compiled from data collected during the NAHMS Dairy 2002 study and takes an in-depth look at the use of antimicrobials on the nation’s dairies. Copies of the report have been shipped to producers and
other industry members across the country.

In 1991, NAHMS conducted the National Dairy Heifer Evaluation Project (NDHEP). Through this project, baseline information on heifer health, illnesses and management practices, as well as prevalence estimates for Cryptosporidium, Escherichia coli 0157:H7 and Salmonella were published.

The NAHMS’ Dairy ’96 study built on the results of the NDHEP. Objectives of the Dairy ’96 study included estimating the national prevalence of Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne’s disease; bovine leukosis virus; and fecal shedding of E. coli 0157 and Salmonella in adult dairy cows.

The NAHMS’ Dairy 2002 study continued to address issues important to the U.S. dairy industry. Dairy 2002 looked at changes in baseline dairy cattle health and management practices; strategies to prevent Johne’s disease; waste-handling systems; the ability of producers to respond to foreign animal diseases; and management factors associated with the presence of certain food-safety pathogens. Here are a few highlights from Part IV: Antimicrobial Use on U.S. Dairy Operations, 2002:

• Of the 8.6 percent of unweaned dairy heifers treated for respiratory disease, 29.3 percent were on operations where florfenicol was the primary antimicrobial used to treat respiratory disease. About one out of five unweaned heifers treated for respiratory disease (17.9 percent) were on operations where tetracyclines were the primary antimicrobial used to treat the disease.
• Of the 13.1 percent of unweaned heifers treated for diarrhea or other digestive ailments, the primary antimicrobials used were sulfonamides (23.8 percent) and tetracyclines (21.9 percent).
• Of the 4.6 percent of weaned dairy heifers treated with antimicrobials for respiratory disease, approximately 3 out of 10 (34.3 percent) were on operations where tetracyclines were the primary antimicrobial used to treat respiratory disease, and one out of four (26.4 percent) were on operations where florfenicol was the primary antimicrobial used. Of the 0.4 percent of weaned heifers treated for digestive disorders, 54.3 percent were on operations that primarily used cephalosporins to treat digestive disorders.
• Of the 15.0 percent of cows treated for mastitis, 55.1 percent were on operations where beta-lactams were the primary antimicrobials used to treat mastitis, and 36.8 percent were on operations where cephalosporins were the primary antimicrobial used. Of the 7.0 percent of cows treated for lameness, beta-lactams, cephalosporins, and tetracyclines (17.3 percent, 29.8 percent and 42.4 percent, respectively) were the most common antimicrobials used.
• A higher percentage of large operations (500 or more cows)— compared to small operations (less than 100 cows) and medium operations (100 to 499 cows)—did not feed medicated milk replacer to unweaned heifers (62.3, 45.6 and 35.9 percent of operations, respectively). Almost half of unweaned heifers (49.2 percent) did not receive medicated milk replacer. When unweaned dairy heifers were fed medicated milk replacer (50.8 percent of all unweaned heifers), oxytetracycline with neomycin was the most common medication used in the milk replacer (23.5 percent of all unweaned heifers).
• Approximately one out of four weaned dairy heifers (26.9 percent) received antimicrobials in heifer rations. A higher percentage of heifers on medium and large operations (35.5 percent and 29.5 percent, respectively) were fed antimicrobials in their rations compared to weaned heifers on small operations (14.7 percent).

Note to Stakeholders: Stakeholder announcements and other APHIS information are available on the Internet. Go to the APHIS home page at http://www.aphis.usda.gov and click the “News” button. For additional information on this topic, contact Teresa Howes at (970) 494–7410 or e-mail teresa.k.howes@aphis.usda.gov

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