Beef Species Symposium I: Cattle Adapted to Tropical/Subtropical Environments
The majority of beef cow herds in South America are constituted by Bos indicus females, which have particular reproductive features that contribute to reduced reproductive efficiency compared with that of B. taurus cohorts. B. indicus heifers reach puberty at an older age compared with B. taurus heifers. Nutritional challenges are critical in cows maintained on low-quality tropical pastures, given that nutrient intake during the postpartum period is not sufficient to meet their requirements for growth and lactation. Several alternatives to enhance reproductive efficiency of B. indicus heifers and cows have been developed to address their inherent reproductive shortcomings. These research-based technologies include: a) hormonal protocols to induce puberty in nulliparous heifers, b) hormonal protocols to synchronize estrus and/or ovulation in B. indicus females to exploit their reproductive responses to artificial insemination, and c) genetic and environmental factors that influence reproductive success in beef herds, including reproductive diseases and excitable temperament of B. indicus females, which have been investigated to support/promote the development of appropriate mitigation technologies. The objective of this presentation is to discuss pharmacological and management technologies to improve reproductive performance of cow-calf systems from tropical areas in South America. Currently, there are hormonal treatments allowing South American B. indicus producers to reach the benchmark of 50% pregnancy rate to TAI, as well as enhance the percentage of cows becoming pregnant to AI at the beginning of the breeding season. This outcome is expected to optimize use of labor, and increase calf weaning age and weight via genetic improvement and concentration of births at the beginning of the calving season.