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

Zh. Gergovska Abstract. The research has been carried out with cows of the Bulgarian black-and-white cattle in 10 farms from various regions in the country. The cows calved in the period 1995 – 2006. A total of 1460 cows are included with 2852 lactations from І-st to ІІІ-rd and respec

Factors affecting duration of the days open and its relation to productive traits in Black-and-White cows Zh. Gergovska