12 The in vitro production of Gyr × Jersey bovine embryos from oocytes collected via ovum pickup for use in the tropics

Milk production in the dairy industry in Africa is much lower than dairy production in the United States (US). On average a dairy cow in the US will produce 60 L of milk daily, compared to the average animal in Africa that produces only 0.6 to 2 L/day. Increasing the efficiency of a dairy herd will not only increase production but could decrease methane production and reduce herd size, in turn taking pressure off the grazing system. By crossing a Bos indicus breed with a Bos taurus breed we are able to take the best of the US dairy genetics and the tropical heat tolerance and disease and parasite resistance of the Gyr, a popular dairy breed in India, to create a hybrid that is well adapted for dairy production in the tropics. The Bos indicus × Bos taurus cross will also allow for greater oocyte yields in future OPU and embryo transfer work compared to the Bos taurus donors used in this study. Therefore, the aim of this study was to produce in vitro Gyr × Jersey (G × J), or Gyrsey™, embryos for use in Africa. A total of 17 Jersey donors were used in this study. The donors were selected at random from the herd and rectally palpated to determine viability of aspiration. A total of 254 oocytes were recovered from the donors via ovum pickup in Wisconsin. Total and viable oocytes per donor averaged 14.94 and 14.18, respectively. The oocytes were then transported to a laboratory at the University of Illinois where IVF was performed. The embryos were produced using a commercial in vitro embryo production (IVEP) protocol. Donor oocytes were kept separate throughout the IVF process. Semen from three similar aged Gyr males was used for the IVF. Donors were paired randomly and then randomly allotted to one of the three bulls. The data is summarised in Table 1. Cleavage and blastocyst rates were evaluated on Days 3 and 7, respectively. Using the commercial protocol, a cleavage rate of 88.19% and a blastocyst rate of 39.29% were achieved. In total, 88 embryos were produced and vitrified (using a commercial vitrification system) for transfer later. In conclusion, the high cleavage rates and blastocysts rates show promise for future embryo transfer work in this project. Large numbers of embryos will be needed to improve the dairy cattle genetics in Africa. The efficiency of the present IVF system will enable that large-scale embryo production. The embryos produced in this study will play a key role in increasing the production efficiency of cattle herds in Africa. The G × J cross allows for an increase in milk production and maintains the heat and disease tolerance necessary for success in Africa with a smaller body frame size. Along with increased production when compared to the native cattle, a lower methane output per unit of milk can also be achieved with the G × J cross.