K. Stankov Department of Management, Faculty of Economics, Trakia University, 6000 Stara Zagora, Bulgaria (Manuscript received 22 August 2020; accepted for publication 16 October 2020) Abstract. A study was conducted on the effect of clinical mastitis at Holstein-Friesian cows on the

T. Penev1*, Zh. Gergovska2, I. Marinov2, V. Kirov3, K. Stankov4, Y. Mitev1, Ch. Miteva1 1Department of Applied Ecology and Animal Hygiene, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Department of Animal Science, Faculty of Agriculture, Trakia University, 6