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.

The objective of this study was to evaluate the effect of the subcutaneous injection of a trace mineral preparation (ITM: Zinc (60 mg/ml), Copper (15 mg/ml), Manganese (10 mg/ml) and Selenium (5 mg/ml)) at dry-off and pre-calving on the occurrence of clinical mastitis and high somatic cell count during the first 30 days post-partum in dairy cows. A randomized field trial was conducted in 2 commercial dairy farms located in Northern Italy, with 280 and 160 Holstein cows respectively with bulk tank SCC greater than 300,000 scc/ml for all year. Cows treated with ITM had lower clinical mastitis occurrence during the first 30 DIM (3.13%) compared to control (CON 12.37%; p = 0.03). New infections during the dry period (ITM 7.50%, CON 20.51%; p = 0.09) and subclinical mastitis at first test day occurrence (ITM 10.99%, CON 17.2% p = 0.22). were numerically lower for ITM, but did not significantly differ.