| Sumario: | Production records of dairy cows from the Mindi Dairy Farms in the Canal Zone, Panama, were statistically analyzed with the principal objective to compare performances between Jersey and Holstein breeds under a humid tropical climate. The milk production records of 315 animals with 1158 lactations were studied. Each breed under consideration had two origins, imported and raised at the Mindi Dairy Farms. Comparisons between origin as well as between breeds were therefore possible.
The data of this study were taken from the individual record cards of all cows that were disposed off during 1947 and 1948. These cards included herd number, date of calving, sex of calf, date of drying, date and cause of disposal and production records taken periodically of the morning milking only. Because the data did not include fat analysis of the milk nor ages, it was not possible to apply correction factors for age to obtain FCM. The lengths of the service period and the dry period were determined. Comparisons were made of the different groups on the bases of averages and coefficients of variability. The type and slope of the lactation curves were determined for comparisons between the groups.
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