The aim of this study was to investigate and compare of the seasonal changes of the fertility performances in Brown cattle raised under the conditions of Elazığ and Susurluk Sugar Factory farms. The investigation material consisted of fertility records of 406 Elazığ and 310 Susurluk from a total 716 on the farms within the period from 1979 through 1984.

The results of the fertility traits were obtained in Brown cattle on Elazığ and Susurluk Sugar Factories farms respectively. The ages at first insemination were 24±0.64 and 23± 0.55 months, the ages of first calving were 34±0.62 and 32 ±0.55 months, the number of inseminations per conception were 1.36 ± 0.00 and 1.63 ± 0.03, the conception rates were 58 and 63%, the percentage of abortion were 1.50 and 4.16%, the calving intervals were 397 ± 5.61 and 398 ± 4.47 days, the first gestation fengths were 283 ± 1.30 and 278 ±1.44 days, the average gestation lengths were 283 ± 0.92 and 281 ± 0.90 days, the first service periods 111 ± 9.60 and 105 ± 8.60 days, the average service periods were 105 ± 4.70 and 110 ± 5.50 days, the intervals from first parturition to first insemination were 69 ± 1.10 and 77 ± 1.95 days, the male calf birth rates were 46.45 and 44.00%

The effects of seasons on the fertility traits were usually non significant. But the same effects on first service period for Elazığ and interval from first parturition to first insemination for Susurluk farms were significant P < 0.05 level. The longest first service period was in the summer, and the longest interval from first parturition to first insemination was in the fall.