Control of estrus in Bos indicus cattle under tropical conditions. Effect of utilization of Norgestomet combined with estrogens

Abstract

The research was carried out in seven cattle ranches in the state of Veracruz. An implant with 6 mg of norgestomet was applied for 9 days to 387 Bos indicus females. Additionally, on the day of the implant application, an intramuscular injection of estradiol valerate (5 mg) and norgestomet (3 mg) was also applied. Detection of estrus was achieved by continuous observation for 96 hours after implant removal. All cows were inseminated between 8 and 12 hours after heat detection. The pregnancy diagnosis was made 45 days after insemination. Within 96 hours of implant removal, 85.8% of the cows showed signs of estrus. The average time interval between implant removal and estrus was 43.9 ± 13.2 hours and 64% of the cows in heat were detected between 1900 and 0700 hours. The conception rate at the first insemination was 25.7% and 22% of all treated cows became pregnant during the first four days after implant removal. The proportion of cows that showed heat was significantly modified by the physiological state of the cows before treatment and 90.2% of the cows that were dry and in cycle showed synchronized estrus after treatment, but only 75.9% of the cows in heat. anestrus and lactation showed heat. after treatment. The physiological state of the cows limits its effectiveness and, although most cows respond by showing estrus, the chances of good fertility are only moderate, especially in these cows. who are in anestrus and breastfeeding when the treatment is applied.