Table I.
List of potential risk factors, total cattle, and test results
| Variable | Levels | Number positive | Number of cattle | % positive |
|---|---|---|---|---|
| Farm size | 30–49 cows | 22 | 460 | 4.8 |
| 50–99 cows | 31 | 577 | 5.4 | |
| 100–199 cows | 8 | 569 | 1.4 | |
| 200 or more cows | 10 | 602 | 1.7 | |
| Farm type | Conventional | 41 | 1750 | 2.3 |
| Organic | 30 | 458 | 6.6 | |
| Cattle group | Sick cow | 1 | 97 | 1.0 |
| Periparturient | 8 | 261 | 3.1 | |
| Healthy lactating cow | 41 | 1445 | 2.8 | |
| Cull cow | 0 | 20 | 0.0 | |
| Preweaned calf | 21 | 385 | 5.5 | |
| Treatment with antibiotics (within 14 d) | Yes | 0 | 80 | 0.0 |
| No | 71 | 2128 | 3.3 | |
| Calf age | 0–14 d old | 3 | 83 | 3.6 |
| 15–28 d old | 3 | 85 | 3.5 | |
| 29–42 d old | 5 | 82 | 6.1 | |
| > 42 d old | 10 | 135 | 7.4 | |
| Parity number | 1st | 16 | 621 | 2.6 |
| 2nd | 9 | 496 | 1.8 | |
| 3rd | 8 | 296 | 2.7 | |
| 4th and up | 16 | 379 | 4.2 | |
| Health status | Diarrhea | 2 | 57 | 3.5 |
| Metritis | 0 | 13 | 0.0 | |
| Mastitis | 1 | 51 | 2.0 | |
| Respiratory problem | 1 | 26 | 3.9 | |
| Lame | 0 | 45 | 0.0 | |
| Other disease | 0 | 24 | 0.0 | |
| Healthy | 67 | 1976 | 3.4 |