Genetic variance and covariance components for across population evaluation of Brown Swiss cattle

• Dairy cattle breeding is an international business, with trade of animal material across populations. Interbull performs international genetic evaluations of dairy bulls, enabling fair comparisons across populations. The bull daughter performances differ between populations and international evaluations therefore require estimation of genetic correlations between the populations. Prerequisites for estimating correlations are knowledge about the genetic variances and covariances within and between populations and the relationship between the bulls. Traditionally, pedigree information has been used to build the relationship matrix connecting included bulls. The recent developments in DNA technology have made it possible to also build genomic relationship matrices using information from the bull genomes. The purpose of this thesis was to evaluate variances and covariances estimated using pedigree or genomic relationship matrices and the effect of factors such as trait heritability, population size, and number of bulls used in more than one population. Moreover, we evaluate the genetic correlations estimated using our different estimates. Genetic variance estimates were compared for a total of 175 population-trait combinations, and genetic covariance and correlation estimates were assessed for four populations and three traits. Phenotypes, genotypes and pedigree were available for 8 864 Brown Swiss bulls originating from Germany-Austria, France, Italy, Slovenia, Switzerland and the United States of America. The results showed that more genetic variance and covariance was explained when the pedigree relationship matrix was used than using the genomic relationship matrix. We found an effect of trait heritability and population size on the genetic variance estimates and an effect of number of common bulls on the genetic covariance estimates. The estimated genetic correlations were similar for both relationship matrices used in the estimation of variances and covariances, indicating that it should be possible to obtain accurate across-population correlation estimates using genomic relationship matrices.

Ämnesord

LANTBRUKSVETENSKAPER  -- Bioteknologi med applikationer på växter och djur -- Genetik och förädling inom lantbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agricultural Biotechnology -- Genetics and Breeding in Agricultural Sciences (hsv//eng)

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