Efeitos da origem e da linhagem do DNA mitocondrial sobre características produtivas e reprodutivas de bovinos leiteiros da raça Gir

Abstract

This study was carried out to evaluate the mitochondrial DNA effect on production and reproduction traits of Gir breed. A total of 3,385 records of milk production (MP), 305-day milk production (305-MP), and lactation length (LL); and 2,394 records of calving interval (CI), milk production per day of calving interval (MPPDCI), and age at first calving (AFC) were analyzed according to mitochondrial DNA origin (indicus or taurus) and cytoplasmatic lineages (foundation cows). The mitochondrial DNA origin was considered as fixed effect for age at first calving analysis. Genetic parameter estimates and predicted breeding values were obtained by restricted maximum likelihood derivative free algorithm using two different animal models (including or not cytoplasmatic lineage effect). Maximum likelihood ratio test showed a non significant effect of cytoplasmatic lineages on all analyzed traits. Cytoplasmatic lineages accounted not significantly for 1.6%, 1.5%, 1.2%, 0%, and 0% of the total phenotypic variance of MP, 305-MP, LL, MPPDCI and AFC. Ranks correlation among breeding values from both models were close to one for all analyzed traits. No mitochondrial lineage model biased upward only estimates of genetic trends of MP, 305-MP, and LL traits. Mitochondrial origin (taurus or indicus) significantly accounted (P<0.05) only for total variation of age at first calving. Cytoplasmatic lineages did not account significantly for the phenotypic variation of any of the studied traits. © 2009 Escola de Veterinária UFMG.