Veterinary Services 

Centers for Epidemiology and Animal Health September 2005 

_________________________________________________________________________________________________________________________ 

Highlights of NAHMS Dairy 2002 

Part IV: Antimicrobial Use on 

U.S. Dairy Operations, 2002 

In 2002, the National Animal Health Monitoring System 

(NAHMS) conducted a study of dairy operations in the 

United States. The Dairy 2002 study was conducted in 

21 major dairy States* and was designed to provide 

information to both participants and industry from 

operations representing 83.0 percent of U.S. dairy 

operations and 85.7 percent of U.S. dairy cows. Data 

were collected between February 25, 2002, and January 

9, 2003. 

 The following are highlights excerpted from Part IV 

of the NAHMS Dairy 2002 study: Antimicrobial Use on 

U.S. Dairy Operations, 2002. Released in September 

2005, this report provides national estimates of 

antimicrobial use on U.S. dairies based on data collected 

during the Dairy 2002 study. 

Unweaned Dairy Heifers 

• A higher percentage of unweaned heifers were 

affected by diarrhea/digestive problems than respiratory 

disease (15.3 percent and 9.0 percent, respectively) 

(Figure 1). However, a higher percentage of unweaned 

heifers affected by respiratory disease received 

antimicrobial treatment than unweaned heifers affected 

by digestive problems (95.6 percent and 85.7 percent, 

respectively). 

 

0

10

20

Treated 

Affected 

Respiratory Diarrhea/other 

digestive problem

Other

Disease or Disorder

Percent

Figure 1. Percentage of All Unweaned Heifers Affected With the Following Diseases 

or Disorders, and Percentage of All Unweaned Heifers Treated With an Antimicrobial 

for the Diseases or Disorders

9.0

15.3

1.0

8.6

13.1

0.8

Navel infection

0.4 0.4

Unweaned Heifers

• 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). 

Weaned Dairy Heifers 

• Diseases and disorders occurred infrequently in 

weaned heifers—only 4.7 percent were affected with 

respiratory disease, 0.8 percent with diarrhea or other 

digestive problems, and 1.5 percent with other ailments. 

Nearly all heifers affected with respiratory disease (97.5 

percent or 4.6 percent of all weaned dairy heifers) were 

treated with antimicrobials, and about half affected with 

digestive problems (50.7 percent or 0.4 percent of all 

weaned heifers) were treated with antimicrobials. 

• 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. 

Cows 

• Mastitis and lameness were the most common 

diseases or disorders affecting dairy cows (16.3 percent 

and 10.9 percent, respectively) (figure 2). Of cows 

affected with mastitis, 91.9 percent were treated with an 

antimicrobial. Of cows affected with lameness, 64.9 

percent were treated with an antimicrobial. 

 

_________________________ 

*California, Colorado, Florida, Idaho, Illinois, Indiana, Iowa, Kentucky, 

Michigan, Minnesota, Missouri, New Mexico, New York, Ohio, 

Pennsylvania, Tennessee, Texas, Vermont, Virginia, Washington, 

Wisconsin 
0

5

10

15

20

Treated 

Affected 

Cows

Respiratory Diarrhea/

Digestive

Reproductive Mastitis Lameness Other

Disease or Disorder

Figure 2. Percentage of All Cows Affected With the Following Diseases or 

Disorders, and Percentage of All Cows Treated With an Antimicrobial for the 

Diseases or Disorders

Percent

2.4 2.2

4.5

2.0

7.3

4.9

16.3

15.0

10.9

7.0

0.6 0.2

• 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. 

Medicated Milk Replacer 

• 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). 

Disease Prevention and Growth Promotion 

• 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, 29.5 percent, respectively) 

were fed antimicrobials in their rations compared to 

weaned heifers on small operations (14.7 percent) 

(figure 3). 

0

20

40

60

80

100

All Operations

Large

Medium

Small

Herd Size

Percent

Yes Did not know No No heifers on operation

Antimicrobials in Heifer Rations

Figure 3. Percentage of Weaned Heifers, by Operations' Use of Antimicrobials in Rations 

for Disease Prevention or Growth Promotion, and by Herd Size

14.7

35.5

29.526.9

1.7 2.0 3.3 2.3

82.6

58.6

62.9

67.6

1.0 3.9 4.3 3.2

• Of the 26.9 percent of weaned dairy heifers that 

received antimicrobials in rations, most (70.4 percent) 

received chlortetracycline. Sulfamethazine and 

oxytetracycline were fed to 32.5 percent and 22.4 

percent of weaned dairy heifers. 

For more information, contact: 

USDA:APHIS:VS:CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NCAHSweb@aphis.usda.gov 

www.aphis.usda.gov/vs/ceah/ncahs

#N441.0905 

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