This study was carried out to investigate milk yield traits and some environmental factors affecting milk yield traits in Brown Swiss cattle reared at the Bahri Dağdaş International Agricultural Research Institute. Between 1987 and 1998, 730 lactation records obtained from 273 cows were evaluated. The least-squares means of measured milk yield, 305-day milk yield, dry period and lactation duration were 3631 kg, 3332 kg, 97.1 days and 313.8 days, respectively. Both year and age statistically affected (P < 0.01-0.001) milk yield and lactation duration, but the calving season was not affected (P > 0.05). The effect of the year on dry period was also significant (P < 0.01), but the effect of age and calving season were not significant (P > 0.05).

This study was carried out to investigate milk yield traits and some environmental factors affecting milk yield traits in Brown Swiss cattle reared at the Bahri Dağdaş International Agricultural Research Institute. Between 1987 and 1998, 730 lactation records obtained from 273 cows were evaluated. The least-squares means of measured milk yield, 305-day milk yield, dry period and lactation duration were 3631 kg, 3332 kg, 97.1 days and 313.8 days, respectively. Both year and age statistically affected (P < 0.01-0.001) milk yield and lactation duration, but the calving season was not affected (P > 0.05). The effect of the year on dry period was also significant (P < 0.01), but the effect of age and calving season were not significant (P > 0.05).