Approximation of reliability of single-step genomic breeding values for dairy cattle in the Czech Republic

The method for approximating reliability of genomic breeding values in the single-step genomic BLUP evaluation was tested on milk production data from dairy cattle in the Czech Republic. The reliability of young dairy bulls without progeny increased by an average of 0.02 for heritability of 0.25 after genomic information was included in the evaluation. The increase was minimal for proven bulls with many progeny because much information was already known about these individuals. The overall increase in the reliability for the entire population of dairy cattle was small, but noticeable;the small increment of the increase resulted from the unfavourable ratio of genotyped bulls and the size of the population (1:2500). A relatively small increase in reliability by genotyping was due to the small number of reference bulls with known genomic information.