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

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.(AU)

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

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.

Programs for fixed-time artificial insemination in South American beef cattle

Fixed-time artificial insemination (FTAI) has been widely applied in South America within the last 20 years for the genetic improvement of commercial beef herds. Most FTAI treatments for beef cattle used in South America are based on the use of progesterone (P4) releasing devices and estradiol to synchronize follicle wave emergence, with pregnancies per AI (P/AI) ranging from 40 to 60%. More recent protocols focusing on extending the interval from device removal to FTAI (i.e. increasing the growing period of the ovulatory follicle) have been reported to improve P/AI in beef cattle. These new protocols and the more traditional FTAI protocols have also been adapted for use with sexed-sorted semen with acceptable P/AI in beef cattle. Finally, color-flow Doppler ultrasonography has been incorporated recently to determine the vascularity of the CL and thereby detect pregnancy as early as Day 22 after the first AI for resynchronization of ovulation for a second FTAI in nonpregnant animals. In summary, FTAI protocols have facilitated the widespread application of AI in South American beef cattle by allowing for the insemination and re-insemination of herds during a defined breeding season, without the necessity of clean up bulls to achieve high pregnancy rates.(AU)

Programs for fixed-time artificial insemination in South American beef cattle

Fixed-time artificial insemination (FTAI) has been widely applied in South America within the last 20 years for the genetic improvement of commercial beef herds. Most FTAI treatments for beef cattle used in South America are based on the use of progesterone (P4) releasing devices and estradiol to synchronize follicle wave emergence, with pregnancies per AI (P/AI) ranging from 40 to 60%. More recent protocols focusing on extending the interval from device removal to FTAI (i.e. increasing the growing period of the ovulatory follicle) have been reported to improve P/AI in beef cattle. These new protocols and the more traditional FTAI protocols have also been adapted for use with sexed-sorted semen with acceptable P/AI in beef cattle. Finally, color-flow Doppler ultrasonography has been incorporated recently to determine the vascularity of the CL and thereby detect pregnancy as early as Day 22 after the first AI for resynchronization of ovulation for a second FTAI in nonpregnant animals. In summary, FTAI protocols have facilitated the widespread application of AI in South American beef cattle by allowing for the insemination and re-insemination of herds during a defined breeding season, without the necessity of clean up bulls to achieve high pregnancy rates.

Assisted reproductive technologies (ART) in water buffaloes

Our expanding knowledge of ovarian function during the buffalo estrous cycle has given new approaches for the precise synchronization of follicular development and ovulation to apply consistently assisted reproductive technologies (ART). Recent synchronization protocols are designed to control both luteal and follicular function and permit fixed-time AI with high pregnancy rates during the breeding (autumn-winter) and nonbreeding (springsummer) seasons. Additionally, allow the initiation of superstimulatory treatments at a self-appointed time and provide opportunities to do fixed-time AI in donors and fixed-time embryo transfer in recipients. However, due the scarce results of in vivo embryo recovery in superovulated buffaloes, the association of ovum pick-up (OPU) with in vitro embryo production (IVEP) represents an alternative method of exploiting the genetics of high yeld buffaloes. Nevertheless, several factors appear to be critical to OPU/IVEP efficiency, including antral follicle population, follicular diameter, environment, farm and category of donor. This review discusses a number of key points related to the manipulation of ovarian follicular growth to improve assisted reproductive technologies in buffalo.

Assisted reproductive technologies (ART) in water buffaloes

Our expanding knowledge of ovarian function during the buffalo estrous cycle has given new approaches for the precise synchronization of follicular development and ovulation to apply consistently assisted reproductive technologies (ART). Recent synchronization protocols are designed to control both luteal and follicular function and permit fixed-time AI with high pregnancy rates during the breeding (autumn-winter) and nonbreeding (springsummer) seasons. Additionally, allow the initiation of superstimulatory treatments at a self-appointed time and provide opportunities to do fixed-time AI in donors and fixed-time embryo transfer in recipients. However, due the scarce results of in vivo embryo recovery in superovulated buffaloes, the association of ovum pick-up (OPU) with in vitro embryo production (IVEP) represents an alternative method of exploiting the genetics of high yeld buffaloes. Nevertheless, several factors appear to be critical to OPU/IVEP efficiency, including antral follicle population, follicular diameter, environment, farm and category of donor. This review discusses a number of key points related to the manipulation of ovarian follicular growth to improve assisted reproductive technologies in buffalo.(AU)

Fixed time artificial insemination and embryo transfer programs in Brazil

Background: Currently, fixed-time protocols for either artificial insemination or embryo transfer can be routinely applied in the reproductive programs on commercial farms. The control of the follicular wave emergency and the induction of ovulation on a pre-determined time without the need for heat detection facilitate the application of such biotechnologies on a large scale basis increasing the reproductive and productive efficiency. This article will discuss the development of reproductive programs that became practical to apply on Brazilian commercial farms as well as the factors that affect its efficiency. Review: Nowadays, Brazil is the world leader on bovine meat market and also in commercial application of biotechnology, such as fixed-time artificial insemination (FTAI) and fixed-time embryo transfer (TETF). In Brazil, there are several hormones commercially available that can be used for manipulation of follicular wave dynamics and induction of ovulation. The evolution of such protocols were also driven towards the decrease on the amount of time that the animals should came to the curral for hormones treatments in order to make it practical to be use on a large scale basis. Among the commercial established synchronization protocols, one of the most commonly used is with the insertion of a progesterone (P4) device associated with an injection of Estradiol Benzoate (EB) at the beginning of the synchronization protocol to induce an emergence of the new follicular wave. Eight days later, the P4 device is removed associated with the intramuscular administration of prostaglandin, equine chorionic gonadotropin (eCG) and Estradiol Cipionate (ECP). In spite of satisfactory follicular manipulation and precisely synchronization of the time of ovulation there are several factors that can affect the efficiency of FTAI or TETF programs. The FTAI pregnancy rate was influenced by the farm as well as by the body condition scores that the cows presented at the beginning of the synchronization protocol. Other important factors that alter the programs results were the bull used and personal performance during artificial insemination. In general, treatments used for FTET are very similar to those applied for FTAI. In the FTET protocols, the main objective is to increase follicular growth and the diameter of the dominant follicle in order to increase P4 concentrations of the subsequent cycle. Some of the strategies used during the evolution of FTET protocol were to superstimulate the growing follicles of the induced wave after the injection of EB at the beginning of synchronization protocol with eCG or to decrease P4 blood concentration increasing LH pulse frequency promoting an increase on the growth of the dominant follicle during synchronization treatment by advancing the PGF treatment. The final result is to have a large pre ovulatory follicle or a pool of follicles in order to produce a single large or multiples functional CL at the time of embryo transfer. The FTET pregnancy rate was influenced by the diameter of the single CL; by recipient superovulation response by the time of year being lower during the months of autumn and winter in relation to the months of spring and summer. Besides, pregnancy rate at 30 days was also affected by the age of the embryo. Additionally, the correct application of cited biotechnologies enhances reproductive efficiency of livestock bringing sustainable and economic return, increasing the viability of the activity. Conclusion: Therefore, the standardization of the procedures is necessary for the commercial application of FTAI and FTET in Brazil being fundamental for obtaining expressive results, so that Brazil could also export such technologies for countries under the same management production system.