Genetic evaluation of Swedish standard-bred trotters for racing performance traits and racing status

The currently applied AM-BLUP methodology for genetic evaluations of the st andard-bred trotters in Sweden was reviewed. The computational procedure fo r multiple trait evaluation of the all-or-non trait racing status and five continuous racing performance traits was described in derail. The procedure involves generating expected Values by the EM algorithm for unraced horses , which are updated in each round of Iteration, in order to facilitate cano nical transformation of records. The validity of the procedure was confirme d by comparing selection based on the multiple trait procedure with selecti on on ST-BLUP (single trait animal model for racing performance), based on records of raced horses only. The MT-BLUP (multiple trait animal model proc edure including racing status and performance as two correlated traits) pro cess was shown to remove bias and increase both the accuracy and precision of selection considerably. The genetic parameters of the current model were evaluated by regressing BLUP solutions from the whole data on solutions fr om subsampled data (method R). The results showed that a slight increase of the currently used heritabilities, maintaining the same covariance structu re, resulted in a very close fit to the expected R-values of one.