Effects of intramammary infusion of Minthostachys verticillata essential oil in cows at drying-off on microbiological and immunological parameters, and milk quality during the subsequent lactation.

This study evaluated the effects of EO administered via intramammary inoculation in dairy cows during the drying-off period and its impact on milk quality in the subsequent lactation. Ten pregnant Holstein cows, free of mastitis, were selected from an organic dairy farm in Córdoba, Argentina. Twenty-four quarters were inoculated with EO: eight received 0.25 g, eight received 0.50 g, and eight received 1.00 g. Control groups included uninoculated quarters and quarters treated with cephapirin. Milk samples were collected before treatment and within 4 days after calving to assess microbial count and somatic cell counts (SCC). The expression of TNF-α, IL-6, and IL-10 was quantified using qPCR and malondialdehyde (MDA) levels were also measured. Blood samples were collected before treatment and within 4 days after calving to determine serum IL-6 and IL-4 levels using ELISA. No significant effects were observed on milk's physical-chemical properties following EO or cephapirin treatment. EO at 1.00 g significantly reduced microbial load (p < 0.05), comparable to cephapirin. SCC increased with all EO doses (p < 0.01, p < 0.05, p < 0.05, respectively). Differential cell counts showed an increase in macrophages after 1.00 g EO treatment. The relative expression of TNF-α, IL-6, and IL-10 decreased without statistical significance. MDA levels significantly increased with cephapirin (p < 0.001), but EO had no effect. Serum IL-6 and IL-4 levels remained unchanged. In conclusion, intramammary EO inoculation enhanced immune response, reduced microbial load, and did not induce lipid peroxidation, suggesting its potential as a preventive treatment for mastitis.