169 OVUM PICK-UP, IN VITRO EMBRYO PRODUCTION, AND EMBRYO TRANSFER IN CATTLE IN TROPICAL AND SUBTROPICAL MEXICO

Abstract

Biotechnology continues to evolve rapidly, allowing the development of artificial reproductive techniques (ART) to increase reproductive efficiency and contribute to the genetic improvement of domestic animals. The present study examines the results obtained after 30 months of starting a commercial practice for ovum pickup (OPU) in vitro embryo production (IVP) and embryo transfer (ET) in cattle in tropical and subtropical Mexico. This research was conducted from 2013–2015 in beef and dairy cattle kept under different environmental and management conditions in 6 states (Chiapas, Oaxaca, Tabasco, Tamaulipas, Veracruz, and Yucatan). Oocytes were collected by OPU, without hormonal treatment, from 10 donor cows: 2 Bos taurus (Bt), 5 Bos indicus (Bi), and 3 Bt × Bi. A total of 98 oocyte recovery sessions were performed on 756 cows and produced 12 524 viable oocytes (1349 GI, 3383 GII, 7792 GIII), which were sent to a central laboratory for IVP. Both conventional and sexed semen were used for IVF, from 9 breeds: 2 Bt, 5 Bi and 2 Bt × Bi. The overall cleavage rate was 69% (8587/12 524). The embryo production efficiency rate was 31% (3905/12 524). Fresh sexed and conventional embryos were transferred to recipients synchronised with the following protocol: Day 0, application of an intravaginal device (ID) with progesterone and 2 mg of oestradiol benzoate IM; Day 8, removal of the ID, 400 IU eCG IM, 0.5 mg cloprostenol sodium IM, and 0.5 mg oestradiol cipionate IM. Day 10 was considered the day of oestrus. Pregnancy rate after ET was 38% (945/3905). The average number of viable oocytes per donor cow was 16.57; the average number of transferred embryos per donor cow was 5.17, and the average number of pregnancies per donor cow was 1.25. The OPU-IVP were successful in producing pregnancies even under several adverse conditions, such as a tropical environment, many donors being prepuberal females and the majority of the adult cows having a previous non-productive history due to hormonal mishandling in superovulation programs or because of overfeeding for show purposes. The consequences of these factors can be observed in the lower overall cleavage rate obtained (69%), compared to the expected (75%). Some variables require further analysis (e.g. different OPU and ET technicians, time of year, cow age, cow breed, and use of conventional and sexed semen). A successful IVP practice has to face and overcome multiple problems that may arise in some geographic locations but, perhaps, not in others. It is interesting to note the use of sexed versus conventional embryos, of the 98 ET sessions, 25 involved sexed embryos versus 73 for conventional embryos. The use of sexed semen for OPU-IVP and ET in this region of Mexico continues to expand.

We thank Genemex Internacional and the ranch owners that were involved with this research.