Table 7.
Associations between isolation of various bacteria from individual calves at 1DOF (n = 1,599 calves) or 13DOF (n = 1,596 calves) and treatment for BRD.
| Risk factor: calf culture positive | OR | 95% CI | p-value | |
|---|---|---|---|---|
| Upper | Lower | |||
| Calf culture positive at 1DOF (n = 1,599) | Outcome: BRD ≤ 13DOF | |||
| M. haemolytica | 0.9 | 0.7 | 1.3 | 0.62 |
| P. multocida | 1.07 | 0.7 | 1.7 | 0.77 |
| H. somni | 0.97 | 0.4 | 2.1 | 0.93 |
| Any bacteria with AMR | 1.8 | 0.9 | 3.6 | 0.09 |
| Any bacteria with macrolide resistance* | 1.4 | 0 | 6.8 | 0.61 |
| Any bacteria with tetracycline resistance | 1.8 | 1.1 | 2.8 | 0.021 |
| Calf culture positive at 1DOF (n = 1,599) | Outcome: BRD ≤ 45DOF | |||
| M. haemolytica | 1.1 | 0.9 | 1.4 | 0.46 |
| P. multocida | 0.9 | 0.6 | 1.3 | 0.65 |
| H. somni | 0.7 | 0.3 | 1.4 | 0.27 |
| Any bacteria with AMR | 0.9 | 0.4 | 2.0 | 0.85 |
| Any bacteria with macrolide resistance* | 0.7 | 0 | 3.2 | 0.36 |
| Any bacteria with tetracycline resistance | 0.8 | 0.5 | 1.5 | 0.55 |
| Calf culture positive at 13DOF (n = 1,596) | Outcome: BRD > 13DOF | |||
| M. haemolytica | 2.1 | 1.3 | 3.3 | 0.004 |
| P. multocida | 2.2 | 1.1 | 4.3 | 0.018 |
| H. somni | 1.6 | 1.1 | 2.4 | 0.028 |
| Any bacteria with AMR | 1.3 | 0.8 | 2.1 | 0.32 |
| Any bacteria with macrolide resistance | 1.2 | 0.5 | 2.7 | 0.73 |
| Any bacteria with tetracycline resistance | 1.2 | 0.6 | 2.2 | 0.66 |
Analysis accounted for year and injectable metaphylaxis administered and adjusts for clustering by pen (N = 16 pens). OR, odds ratio; 95% CI, 95% confidence interval. *Exact logistic regression (SAS® version 9.4, Cary, NC, United States). See details for other fixed effects and measures of model fit in Supplementary Table S7.