Journal of Dairy Science, Vol 74, Issue 4 1420-1427, Copyright
© 1991 by American Dairy Science Association
Animal model evaluations for Mexican Holsteins
R. L. Powell and G. R. Wiggans
Improvement Programs Laboratory, Agricultural Research Service, USDA,
Beltsville, MD 20705.
Genetic evaluations for milk yield of Holsteins in Mexico were computed
from lactation and pedigree information from Holstein de Mexico. 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).