Effect of trace mineral injection during the dry period on the occurrence of clinical mastitis in the first 30 days post-partum in dairy cows.

Trace mineral injection at dry-off significantly reduces early postpartum clinical mastitis in dairy cows.

This randomized field trial evaluated the efficacy of subcutaneous trace mineral injection (containing zinc, copper, manganese, and selenium) administered at dry-off in reducing mastitis incidence in dairy cows. The study enrolled 440 Holstein cows from two commercial dairy farms in Northern Italy with persistently elevated bulk tank somatic cell counts (>300,000 cells/ml). Cows receiving trace mineral treatment demonstrated significantly lower clinical mastitis incidence during the first 30 days in milk (3.13% vs 12.37%, p=0.03). While new infections during the dry period and subclinical mastitis at first test day were numerically lower in the treated group, these differences did not achieve statistical significance. These findings suggest that peripartum trace mineral supplementation may reduce clinical mastitis risk during the critical early lactation period, likely through improved immune function and epithelial barrier integrity. However, the lack of statistically significant differences in dry period infections and subclinical mastitis suggests the mechanism may be multifactorial. Further research with larger sample sizes and extended follow-up periods would strengthen these preliminary findings.

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