Özet:

The study was carried out at Bala State Farm to investigate the effect of seasonal conditions on reproductive traits of Holstein cattle in Middle Anatolia. The data relating to reproductive traits were recorded in 1992. İn addition to farm records of reproductive performance in the period of 1985-1991 were also used According to the results, the shortest and longest first conception ages were found in the autumn and winter inseminated group, respectivelly. The first calving age was found 860.7 days in spring and 886.7 days in autumn calving groups. The differences for both traits were not significant among season groups. Service periods in spring and summer groups were longer than in winter and autumn groups. The differences among season groups were statistically significant (P<0.01). The number of inseminations per conception were ranged from 1.5 to 1.8Mand from 1.3 to 1.9 in season and year groups, respectivelly. The significant differences were observed only among the year groups (P<0.01). The differences for calving, abortion, stillbirth and twinning rates were not significant among the season groups. The conception rates in summer and autumn insemination were higher than winter and spring groups. The differences for conception rates among season groups were significant (P<0.05). The shortest calving interval was obtained in autumn, the longest period was obtained in spring calvings; gestation period was the shortest in summer group and Iongest in winter group and the differences for both traits were significant among season groups (P<0.05).

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