Animal model evaluations for Mexican Holsteins.

Genetic evaluations for milk yield of Holsteins in Mexico were computed from lactation and pedigree information from Holstein de México. The US animal model system for national evaluations was adapted for Mexico. The primary change was in defining unknown-parent groups. Paths of unknown parents of bulls and sires of cows were combined and separate unknown-parent groups defined for parents of US, Canadian, and Mexican registration. Records with fewer than 305 d were expanded around management group mean; a lower limit of 50% of management group mean was imposed on these records. Based on 123,397 lactation records by 50,538 cows, evaluations were computed for 68,020 cows (including those without lactation records) and 4573 bulls. Estimate of breeding value improvement in 1986 from a quadratic curve was 87 kg milk. Animal model estimates of breeding value by birth year were similar to Modified Contemporary Comparison estimates. Correlations with previous evaluations were .90 for bulls and .85 for cows. Differences resulted from added data as well as changes in evaluation method. Cows born in 1985 with US sires had predicted breeding values for milk 380 kg higher than those with Canadian sires and 336 kg higher than those with Mexican sires. Equations were developed to convert milk PTA between Mexico and the US. No sire by country interaction was found; correlations of US and Mexican PTA were .90 (expected) and .91 (actual).