A study on the genealogical structure and variance of the selected traits of the East Bulgarian riding breed. III. Genetic determination of the basic body measurements and of the correlations among them
2009
Sabeva, I., Agricultural Institute, Shumen (Bulgaria)
The analyzed data set included information for the traits height at withers, cross body length, chest girth and shank girth of 425 horses from the East Bulgarian Riding breed. The studied horses from the Kabiuk and Stefan Karadja breeding studs had completed their 2nd and 3rd year of age during the last two generation intervals. Mixed model methodology was used for the analysis of variances and for calculation of the heritability phenotypic and genetic correlations. Low additive variances were found for the traits height at withers, cross body length and chest girth and a medium one for the shank girth at two years of age. The genetic correlation between the height at withers and the cross body length was average in magnitude. A complex interaction of the genotype with the environment or other inter-allelic interactions were observed for the correlations between the height at withers and the shank girth -0.13, and between the cross body length and the shank girth -0.30. The phenotypic correlations between the studied traits containing also the environmental correlation effect were within 0.43 - 0.66. After the selection carried out the coefficients of heritability for the traits height at withers and shank girth were negligibly higher compared to the estimated values at two years of age. The additive variance was twice higher for cross body length and chest girth. No considerable differences were observed between the phenotypic correlations at the two age categories. The changes in the genetic correlations were more considerable. The results of this study showed that the determination of the genetic parameters for the body measurements before and after the first stage of selection could give an opportunity for obtaining more complete information not only for the genetic tendencies in the inheritance, but also for elucidation of the nature of the genetic variance of the traits.
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