[Reproductive performance of Bos taurus x Bos indicus cows under an artifical insemination program following synchronized of natural estrus in the dry tropical condition of Costa Rica] | Comportamiento reproductivo de vacas Bos taurus x Bos indicus bajo programas de inseminacion artificial a estro sincronizado y natural en condiciones del tropico seco de Costa Rica

English. To evaluate the reproductive performance of beef cows artificially inseminated in dry tropical conditions in Costa Rica, 3080 records were used related to 8 programs of artificial insemination (AI) of cows of five or more years of age. Of these records, 28 were eliminated due to inconsistent data, so in the end only 3052 records were taken into account to be analyzed. Percentage of synchronized and pregnant cows were calculated. Gestation length was calculated (2367 records) on animals which had insemination and calving dates. Almost 20% (605/3052) of the cows were treated with prostaglandin F2 alpha; out of them, 61% (371/605) was detected in heat between 72 and 168 h post-treatment. Seventy seven percent (101/131) of the treated cows that failed to hold service showed estrus again after 17 and 23 days. Seventy seven point three percent (686/888) prostaglandin F2 alpha non treated cows, that failed to hold service, also showed estrus after 17 and 23 days. Overall conception rate was 80.2% (2448/3052), whereas at first and second services, figures were60.5% and 67.1% respectively. In the treated cows that were detected in heat between 3 to 7 days post-treatment, the conception rate wa 87% (324/371). In the rest of the group, including treated and non treated cows outside the period of 3 to 7 days, the conception rate was about 81%. The overall number of services per conception was 1.6. Nevertheless, only 77% of the gestations were found to be between 261 and 290 day suggesting that the high conception rates observed in this experiment were not necessarily a consequence of the AI program

Spanish; Castilian. Para evaluar el comportamiento reproductivo de vacas cebuinas bajo programas de inseminacion artificial (IA) en el tropico seco de Costa Rica, se utilizaron 3052 registros correspondientes a ocho programas de inseminacion artificial de vacas adultas de 5 o mas anos de edad y se calcularon los porcentajes de animales sincronizados y gestantes. Asimismo, la duracion de la gestacion fue calculada de 2367 registros que contaban con fecha de inseminacion y parto, respectivamente. El 19.8% (605/3052) de las vacas fueron sincronizadas con prostaglandina F2 alfa, 61% (371/605) fueron detectadas en celo entre las 72 y 168 horas postratamiento. El 77% (101/131) de vacas sincronizadas que repitieron celo fueron registradas entre 17 y 23 dias. El 77.3% (686/888) de vacas no tratadas y que repitieron celo, fueron registradas entre 17 y 23 dias. El porcentaje de concepcion general fue de 80.2 (2448/3052), al primero y segundo serbicios fue de 60.5 y 67.1, respectivamente. En las vacas tratadas que presentaron celo en el periodo de 3 a 7 dias postratamiento, el porcentaje de concepcion fue de 87 (324/371), y el grupo restante, que incluye hembras que mostraron celo fuera del periodo de 3 a 7 dias incluyendo vacas tratadas y no tratadas, fue de 81 (2111/2619). El numero de servicios por concepcion general fue de 1.6. Sin embargo, solamente 77% de las vacas tuvieron una duracion de la gestacion entre 261 y 290 dias, sugiriendo que altas tasas de concepcion posiblemente no sean producto directo de la I.A.