The use of tablets with active substances as an alternative to the use of antibiotics is an increasingly common method of preventing mastitis in modern milk production. The slow release of active substances enables prolonged action of such medicine. The aim of this master' thesis was to determine the effectiveness of using tablets with bioactive substances such as niacinamide, inulin, salicin and antioxidants gingerols, shogaols, zingerone, on production parameters and health status of dairy cows. The research was conducted on a small family farm in central Istria. In the research participated 20 cows, divided into two groups according to age, and each cow had its own control cow. The milk of the treated cows was analyzed at the Centre for Quality Control of Livestock Products Križevci every 15 days for a period of 60 days from the application of the bolus. The statistical significance of the influence of age on the production of the daily amount of milk and the number of somatic cells in the milk of older cows was determined. The number of somatic cells, as an indicator of subclinical mastitis, fell in both test groups from the beginning to the end of the study. In older cows, the decrease was 76.84%, and in younger cows, it was 14.63%. The obtained results indicate the improvement of the health status of cows and the potential of using bolus with bioactive substances in intensive milk production.