The objectives of this study were to detect milk production and fertility traits of Jersey breed raised in Turkey and to investigate effects of some environmental factors on these traits. For this purpose, production records of Jersey cows were collected digitally from herd management programme for milking management system of Karaköy Agricultural Enterprise. Total 1926 milk yield records from 820 lactations of 303 cows and 1382 fertility records from 1021 calving terms of 365 cows were used in this study.

Least square means for 100-day milk yield 1334.16±13.14 kg, 200-day milk yield 2591.17±22.76 kg, 305-day milk yield 3793.79±42.83 kg, first calving age 832.617±5.093 days, open days 101.098±6.008 days, calving interval 370.302±2.012 days were detected.

The effects of lactation number, calving year and season were found significant at different levels on 100 and 200-day milk yield (P<0.05, P<0.01 and P<0.001). The effects of lactation number and calving year were significant on 305-day milk yield (P<0.01). The effects of calving age were not found significant on all milk production traits. While the effects of calving year were significant on first calving age (P<0.001), the effects of calving season were not significant. While the effects of calving season (P<0.001) and lactation number (P<0.05) were found significant on open days, the effects of calving age and year were not significant. The effects of lactation number, calving age and year were significant on calving interval (P<0.001).