TABLE 3.
Negative-binomial-regression model for the association between cattle type, beneficial management practices, and precipitation and instantaneous load of Giardia spp. (cysts/s) discharging from dairy cattle high-use areas during runoff conditions from 2002 to 2004 in Tomales Bay, CA
| Risk factor | Coefficient | 95% CIb | P valueb |
|---|---|---|---|
| Type of dairy cattle | |||
| Cow, milking or drya | 0.0 | ||
| Cow, calving | −3.54 | (−4.63, −2.46) | <0.001 |
| Calf, 2.1 to 6.0 mo of age | −0.67 | (−1.97, 0.64) | 0.32 |
| Calf, 0.1 to 2.0 mo of age | 4.37 | (2.87, 5.87) | <0.001 |
| Length of vegetated buffer (m) | −0.23 | (−0.30, −0.17) | <0.001 |
| No. of cattle in lot | 0.02 | (0.009, 0.04) | 0.002 |
| 24-hour precipitation (mm) | 0.22 | (0.08, 0.37) | 0.003 |
| 24-hour precipitation2 (mm2) | −0.004 | (−0.007, −0.001) | 0.009 |
| Cumulative annual precipitation (mm) | −0.02 | (−0.03, −0.006) | 0.004 |
| Cumulative annual precipitation2 (mm2) | 0.00002 | (0.000001, 0.00003) | 0.04 |
| Constant or intercept term for the model | 4.37 | (2.23, 6.51) | <0.001 |
a
Referent condition for the categorical variable, type of dairy cattle.
b
Adjusted for potential lack of independence due to repeated sampling of high-use areas across storms.