Table 3.
Bacterial isolates from quarter milk samples of subclinical mastitis cows separated into farm groups comprising i) normal use (NORM), being no more than 2 times/cow/yr of antibiotic use, and ii) excessive use (HIGH), being more than 2 times/cow/yr
| All
|
NORM
|
HIGH
|
p-valuea | ||||
|---|---|---|---|---|---|---|---|
| N | Percent | N | Percent | N | Percent | ||
| Negative sample | 204 | 65.2 | 96 | 62.3 | 108 | 67.9 | 0.34 |
| CNS | 31 | 9.9 | 21 | 13.6 | 10 | 6.3 | 0.03 |
| Staph. Aureus | 17 | 5.4 | 13 | 8.4 | 4 | 2.5 | 0.02 |
| Strep. Uberis | 30 | 9.6 | 12 | 7.8 | 18 | 11.3 | 0.33 |
| Strep. Dysgalactiae | 10 | 3.2 | 7 | 4.6 | 3 | 1.9 | 0.21 |
| C. bovis | 14 | 4.5 | 0 | 0.0 | 14 | 8.8 | <0.01 |
| Other streptococci | 3 | 1.0 | 2 | 1.3 | 1 | 0.6 | 0.62 |
| Gram negative bacteria | 4 | 1.2 | 3 | 2.0 | 1 | 0.6 | 0.74 |
| Total | 313 | 100.0 | 159 | 100.0 | 154 | 100.0 | |
a
Comparisons of specified bacteria between HIGH and NORM.