Fixed time artificial insemination and embryo transfer programs in Brazil
Nasser, Luis FernandoPenteado, LucianoRezende, Carlos RSá Filho, Manoel FBaruselli, Pietro S
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.
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