Selenium deficiency is a common nutritional disorder in dairy cattle globally. However, sele- nium supplementation can lead to selenium toxicity. This study evaluated a novel, low-toxicity selenium supplement, selenitetriglycerides, to determine its efficacy and safety in dairy cows. The study was conducted on 12 Holstein Friesian cows divided in two equal groups (control group without supplementation of selenium and experimental group with supplementation of selenitetriglycerides). Experimental cows (n=6) were orally administered 300 mg/cow/day of selenitetriglycerides for 14 days (days 1-14) and then monitored for a further 14 days (days 15-28). Blood from both groups of cows was sampled for determination of selenium concentra- tions, activity of aspartate aminotransferase, creatine kinase, lactate dehydrogenase, gamma-glutamyl transferase, concentrations of triglycerides, cholesterol, non-esterified fatty acids, glucose, total protein, urea, creatinine and hematological parameters. Serum selenium concentra- tions in the experimental group increased significantly on day 2 (from 64.92±6.89 μg/L to 127.95±13.75 μg/L), peaked on day 7 (266.22±14.21 μg/L) and remained significantly above the initial baseline values (day 1) for 28 days. Serum selenium concentrations in the control group did not change significantly during the 28 day period (65.22 μg/L on 1st day and 64,35 μg/L on 28th day) and were significantly lower than those in the experimental group from day 2 to day 28. The results of clinical examinations, analyses of hematological parameters, and liver and kidney function tests showed that selenitetriglycerides had no adverse effect on the health or on the metabolic or haematological statuses of the cows. These findings indicate that sele- nitetriglycerides are safe and effective selenium supplements for cattle.