Evolution of knowledge on ovarian physiology and its contribution to the widespread application of reproductive biotechnologies in South American cattle

Abstract

As our understanding of ovarian function in cattle has improved, our ability to control it has also increased. Luteal function in cattle has been studied in detail, and prostaglandin F2α has been used for several years for the elective induction of luteal regression. More recently, follicle wave dynamics has been studied and protocols designed to induce follicular wave emergence and ovulation have reduced, and even eliminated, the need for estrus detection. The addition of progestin-releasing devices, estradiol, GnRH and equine chorionic gonadotropin (eCG) have provided opportunities for fixed-time AI (FTAI) and possibilities for increased pregnancy rates. In embryo transfer programs, these same treatments have eliminated the need for estrus detection, permitting fixed-time embryo transfer and the initiation of superstimulatory treatments without regard to day of the estrous cycle. Collectively, new treatment protocols have facilitated the application of assisted reproductive technologies, and this is especially true in South America. Over the last 20 years, the use of AI in South America has increased, due largely to the use of FTAI. There has been more than a 10-fold increase in the use of FTAI in Brazil with more than 11 million treatments in 2016, representing 85% of all AI. Similar trends are occurring in Argentina and Uruguay. Production of in vivo-derived (IVD) embryos has remained relatively stable over the years, but in vitro embryo production (IVP) has increased dramatically over the past 10 to 15 years, especially in Brazil where more than 300,000 IVP embryos were produced in 2010. World-wide, more than 666,000 bovine IVP embryos were produced in 2016, of which more than 57% were produced in South America. The use of assisted reproductive technologies has facilitated the dissemination of improved genetics and increased reproductive performance; other South American countries are now following suit.

Challenges to increase the AI and ET markets in Brazil

“…Uruguay has approximately 3 million breeding females and 300,000 TAI, demonstrating that approximately 10% of breeding females in reproduction are inseminated. In total, more than 15 million breeding females were inseminated using TAI in Brazil, Argentina and Uruguay in the year 2017 (Mapletoft et al, 2018). This information indicates the consolidation of the technology in the market, resulting in economic gains and positive perspectives for livestock.…”

Effect of follicular growth promoters on timed artificial insemination in dairy cows.

“…La FSH utilizada en el presente estudio, por otro lado, contenía el 87% de FSH, y su metabolismo parece ser rápido, ya que, después de la administración intramuscular, la vida media y la desaparición de la FSH se estimaron en 5 y 12 minutos, respectivamente (23,24). Estas diferencias de semivida entre eCG y FSH se informaron en estudios de protocolos superovulatorios, en los que una dosis única de eCG intramuscular fue suficiente para estimular el crecimiento de múltiples folículos (25,26), mientras que para superovular vacas con FSH es necesario utilizar varias administraciones intramusculares (27).…”

Influence of breastfeeding and postpartum anestrus on the reproductive efficiency of the bovine female

“…Os mecanismos de controle do anestro pós-parto envolvem uma complexa relação entre hipotálamo, hipófise, ovário e útero. No pós-parto, os estoques de LH e FSH da hipófise estão reduzidos devido ao feedback negativo do estradiol (E2) no hipotálamo e das elevadas concentrações de progesterona (P4) no final da gestação (Mapletoft et al, 2018;Nett et al, 1988;Sartori & Barros, 2011).…”