I. Marinov*, Zh. Gergovska
Department of Animal Science – Ruminants and Dairy Farming, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
Abstract. The study included 514 Black-and-White cows from 14 farms of different regions of the country. The cows are on Ist (224), IInd (194) and IIIrd (96) lactation, respectively. A scoring of 24 linear type traits on a scale from 1 to 9 was performed. The average age of first calving (AFC) for all farms included in the study was 880.8 days or 29.4 months. By farms the average age varies from 729.1 to 1266.7 days. A statistically significant effect of age at first calving on the following linear type traits was found: chest width, body depth, rump angle, rump width, fore udder attachment, rear udder height and rear udder width. Between AFC and linear traits stature, chest width, rump angle, rear legs rear view, bone structure, rear udder height, rear udder width and BCS significant negative phenotypic correlations with low to moderate values from -0.12 to -0.27 were reported. Between AFC and the traits fore udder attachment and teat length a significant positive phenotypic correlation of 0.17 and 0.13, respectively, was reported. Cows calved for the first time at an optimal age from 24 to 30 months of age had a wider chest, deeper body, wider rump and rear udder and wider and parallel placed rear legs and thinner and refined bones. The higher age of first calving – over 35 months was not associated with better development of the cows.