Comparison of milk yield parameters of imported Estonian and American Holsteins in response to same sire insemination

The aim of the study was to evaluate the milk yield parameters of imported Estonianand American Holsteinsin response to same sire insemination. The means for 305-day milk yield produced by the groups were between 8180 and 10851 kg, which points out a yield higher than most of those reported in the literature. American Holsteins were superior to Estonian cows with 2036 kg more milk in the first and 1147 kg in the second lactation period. For environmental factors, calving age itself had no augmenter effect on milk yield unless it was accompanied by parturition. The calving season and dam age had no significant effect on milk yield, but longer dry periods generally resulted in more milk yield. Fat, protein and lactose components were determined as 3.7, 3.3 and 4.6% during the first and second lactation periods. Asa result, theimported breeds produced high milk yield performance with optimal components in Nigde province.