COMPARISON OF 2 MODELS FOR ESTIMATION OF VARIANCE-COMPONENTS IN A SAMPLE OF SPANISH HOLSTEIN-FRIESIANS

Two models for estimating genetic parameters in animal populations wer e compared. The cheapest, in terms of computing costs, was based on a sire model and the most expensive on an animal model. In order to chec k the accuracy of both methods they were applied to the best available sample of Spanish Friesian cattle. Milk production of each cow, as we ll as fat contents were simulated using prior estimates of genetic add itive, permanent environment and residual variances, keeping the actua l mating scheme, so that the simulation mimicked the actual population structure. Results, under the above premises, show no advantages of t he more costly procedure over the cheaper one, suggesting that a sire model based estimating procedure for genetic parameters may be preferr ed when a small number of individuals, little pedigree information and highly disequilibrated distribution of effects characterize the data.