APPROXIMATE ACCURACY OF GENETIC EVALUATION UNDER A SINGLE-TRAIT ANIMAL-MODEL

A method to approximate breeding value accuracy under a single-trait animal model was developed. Meyer's method was extended to account explicitly for the covariance between contemporaries, the distribution of relatives across herds, exact relationships between animals, and some cases of close inbreeding. The procedure comprised five steps. The diagonal term of each animal in the mixed model equations was progressively adjusted for 1) the herd-year-season effect, 2) contemporaries, 3) progeny and contemporaries of progeny, 4) mates, and 5) parents and parents of contemporaries, before being inverted and expressed in term of repeatability. The efficiency of this method and Meyer's method was compared with two examples. The proposed method appeared to be more efficient, particularly when herds were small, progeny concentrated in a few herds, and animals inbred. Estimates of repeatability from both methods were biased upward and remained sensitive to the number of generations included in the analysis. However, because of its ease of use, Meyer's method, with simple adjustments for repeatability level and inbreeding, can be recommended.