Table 4.
Results of logistic regression for the effect of dry-off protocols on mammary gland health indicators (bacteriological and SCM cure and new cases of SCM).
| Variable | Item | Estimate | SE a | p-Value | OR b (95% CI c) | LSM d (SEM e) |
|---|---|---|---|---|---|---|
| Bacteriological cure f | ||||||
| β g | 2.21 | 1.04 | ||||
| Treatment | ADCT h | −0.84 | 0.46 | 0.07 | 0.43 (0.17–1.08) | 0.89 (0.03) |
| SDCT i | Ref. | 0.95 (0.02) | ||||
| Quarter position | Front | −0.78 | 0.44 | 0.07 | 0.46 (0.20–1.09) | 0.89 (0.03) |
| Rear | Ref. | 0.95 (0.02) | ||||
| Dry period | 0.02 | 0.02 | 0.27 | 1.02 (0.99–1.05) | ||
| SCM cure j | ||||||
| β | 2.31 | 0.34 | ||||
| Treatment | ADCT | −0.22 | 0.26 | 0.40 | 0.80 (0.48–1.34) | 0.85 (0.02) |
| SDCT | Ref. | 0.87 (0.02) | ||||
| DIM k | 0.00 | 0.00 | 0.19 | 0.99 (0.99–1.00) | ||
| New SCM case l | ||||||
| β | −1.43 | 0.41 | ||||
| Treatment | ADCT | −0.02 | 0.28 | 0.94 | 0.98 (0.56–1.70) | 0.13 (0.02) |
| SDCT | Ref. | 0.13 (0.02) | ||||
| DIM | 0.00 | 0.00 | 0.21 | 0.99 (0.99–1.00) |
a SE: Standard error; b OR: Odds ratio; c CI: Confidence interval; d Least square mean; e Standard error of the mean; f Bacteriological cure: a mammary quarter was considered bacteriologically cured when the microorganism identified at drying off was not isolated in either of the two postpartum milk samples; g β: Regression coefficient; h ADCT: 0.25 g anhydrous cefalonium; i SDCT: 0.25 g anhydrous cefalonium used in combination with ITS (bismuth subnitrate 4 g); j Subclinical mastitis cure: considered when MQs with SCC >200,000 cells/mL before drying off had reduction to values ≤200,000 cells/mL after calving; k Days in milk; l New subclinical mastitis case: defined when MQ had SCC ≤200,000 cells/mL before drying off, with an increase to >200,000 cells/mL after calving; Variables with p-value > 0.30 were excluded from the final model.