TAILIEUCHUNG - Báo cáo sinh học: "Connectedness among herds of beef cattle bred under natural service"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học quốc tế đề tài: Connectedness among herds of beef cattle bred under natural service | Tarrés et al. Genetics Selection Evolution 2010 42 6 http content 42 1 6 GSE Ge n et i cs Selection Evolution RESEARCH Open Access Connectedness among herds of beef cattle bred under natural service Joaquim Tarrés Marta Fina Jesus Piedrafita Abstract Background A procedure to measure connectedness among herds was applied to a beef cattle population bred by natural service. It consists of two steps a computing coefficients of determination CDs of comparisons among herds and b building sets of connected herds. Methods The CDs of comparisons among herds were calculated using a sampling-based method that estimates empirical variances of true and predicted breeding values from a simulated n-sample. Once the CD matrix was estimated a clustering method that can handle a large number of comparisons was applied to build compact clusters of connected herds of the Bruna dels Pirineus beef cattle. Since in this breed natural service is predominant and there are almost no links with reference sires to estimate CDs an animal model was used taking into consideration all pedigree information and especially the connections with dams. A sensitivity analysis was performed to contrast single-trait sire and animal model evaluations with different heritabilities multiple-trait animal model evaluations with different degrees of genetic correlations and models with maternal effects. Results Using a sire model the percentage of connected herds was very low even for highly heritable traits whereas with an animal model most of the herds of the breed were well connected and high CD values were obtained among them especially for highly heritable traits the mean of average CD per herd was for a simulated heritability of . For the lowly heritable traits the average CD increased from in the single-trait evaluation to and in the multi-trait evaluation with moderate and high genetic correlations respectively. In models with maternal effects the .

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