Impact of adopting non-antibiotic dry-cow therapy on the performance and udder health of dairy cows.

Background: On dairy farms, the prophylactic use of antibiotics at drying-off is being increasingly challenged. The objective of this study was to examine the effect of antibiotic dry-cow therapy (DCT) or non-antibiotic DCT on dairy cow performance and udder health.

Methods: Holstein cows (n = 285) with low risk of intramammary infection (<200,000 cells/ml) were assigned to one of two treatments, either antibiotic DCT (A + TS; antibiotic treatment in combination with internal and external teat sealants) or non-antibiotic DCT (TS; internal and external teat sealant only).

Results: There was no statistically significant (p > 0.05) difference between treatments for mean cow milk yield, composition or energy corrected milk yield. Mean somatic cell count was 0.16 log higher in the TS treatment (95% confidence interval [CI]: -0.00 log to -0.33 log ) compared to A + TS treatment (p = 0.047). A 50% increase in the number of mastitis cases was observed in the A + TS treatment compared to TS treatment (odds ratio = 1.5, 95% CI: 0.80%-3.01%), although this was not significant. There was no statistical evidence (p > 0.05) that treatment had any effect on colostrum quality and composition.

Conclusion: Results indicate that non-antibiotic DCT can be adopted in 'low-risk' cows who were offered grass silage-based diets in cubicle accommodation, with low risk of adverse effects on performance or udder health.