Selection in the genetic resource: genetic variation of the linear described type traits in the Old Kladrub horse

Abstract. The structure of the breed in 2003 was: 39 sires and 350 dams. The breed was closed against immigration in 1992. In 1993 and 2003 coefficients of inbreeding (F_x) were calculated from 5 parental generations for sires and dams in the whole breed and white and black variety. From 1993 to 2003 decreased the F_x (%) in the breed for stallions from 5.65 to 5.57 and for mares from 7.75 to 4.88. The effective population size was in 1993 N_e=114.00 and 2003 N_e=140.36. The increment of N_e during the 10-year period was 26.36 animals. The average heterozygosity estimated on the frequencies of blood types, biochemical markers and microsatellites was enough large and was connected with a low coefficient of inbreeding. Linear type evolutions of 494 horses of the Old Kladrub breed for 32 traits were used to analyse the effect of variety and stud. The data were used for the estimation of population parameters and heritability coefficients. The specific properties and variation of the Old Kladrub horse in its current state were characterized by the overall mean, standard deviation, coefficient of variation, number of utilized scores and heritabilities. The highest coefficient of variation showed the forelimbs-side view (40.14 %), chest girth (36.25 %) and height at withers (30.97 %). The 8 traits showed heritabilities within the interval of 0.20 to 0.68. These traits are candidates as selection criteria. Significant differences between both varieties were found in 13 from 32 traits. Significant differences were found in 12 of 32 traits between the Kladruby stud and the private studs.