Abstract
276 377 Mexican records for 1969-1983 calvings were utilized to evaluate performance and 53 470 first lactations were used to estimate genetic parameters. Means and standard deviations for milk yield (kg), days in milk, days dry, calving interval, days pregnant and age at first calving were evaluated. Heritabilities for milk yield, lactation length (LL), age at first calving (Age), and days carried calf (DCC), were calculated as well as genetic and phenotypic correlations between traits. Sires with ten or more daughters were evaluated by best linear unbiased prediction (BLUP) procedures. Predicted sire values (SV) for milk ranged from 731 to -911 kg. Average difference in SV between sires was small (4 kg) but large (16 kg) between the top 20 sires. Considerable genetic improvement could be achieved.
