Duration of gestation in Jersey and Holstein in the State of Rio de Janeiro

Abstract

The duration of 473 gestation periods of 231 inseminated Jersey and Holstein cows on three farms in the State of Rio de Janeiro were tabulated. Jersey cows presented a mean of 279,00 ± 0,46 days of gestation. The mean gestation for the Holstein cows was 282,35 ± 0.52 days. The difference between breeds was highly significant (P<0.01). The sex of the calf had a significant effect on the duration of pregnancy: males were carried on 279,44 ± 0.60 and 283.33 ± 0.74 days and females 278,82 ± 0.71 and 281,15 ± 0.72 days in the Jersey and Holstein cows respectively. There were highly significant differences between the mean gestation periods of herds of the some breed. Differences in gestation period for male and females calves produced by the same cow were significant (P<0,05). The month of conception had no statistically significant effect on gestation.