OPU-IVF is performed within eight days. Oocytes are collected by OPU, and matured for one day before being fertilized; the embryos are transferred seven days after fertilization. The pregnancy rate is expected to be 45-50% after ET with fresh IVF embryos. When embryos are frozen, the pregnancy rate usually drops, but with RLI’s vitrification kit, it can be kept at a level of 40% with vitrified OPU-IVF embryos.
Outline of Bovine OPU-IVF and ET Procedures
OPU has been shown to be a valuable technology greatly enhancing the potential of IVF systems (OPU-IVF) in a variety of breeding conditions in cattle. The advantage of OPU-IVF system has been outlined as optimized efficiency for embryo production in vitro (IVP), i.e. a few of sperm used for IVF, more number and quality of collected oocytes for fertilization, more frequent collections from hormonal stimulated donor.
OPU-IVF has been a successful IVP system to produce embryos in Bos Indicus breeds, such as Brahma cattle, because an average of 30-40, even up to 200 COCs are aspirated from one donor in a signal OPU session. It was not efficient with Bos Taurus breeds. However, the number and quality of collected oocytes collection have been improved dramatically. The dominant follicle and all the other large in a donor animal are usually removed; subsequently the animal is injected with six shots of FSH to stimulate the growth of follicles. The dominant follicle removal by mechanical ablation and FSH treatment is an excellent way to coordinate the beginning of the next follicular wave 1.5 to 2 days later. As a result, an average number of 20 COCs is usually collected from one OPU session. The donor animals are aspirated in every other week.
The oocyte collection is varied among the donors by OPU. Embryo development of OPU oocytes after IVF is influenced by the sires for fertilization.
Efficiency of Embryo Production with OPU-IVF vs. MOET
During the OPU-IVF practice, an average 25 follicles are aspirated, and 20 oocytes are collected for IVF in each OPU session. With the development rate of 30% to blastocyst stage, average 6 embryos are transferable for ET or freezing procedures. The donor can be used for OPU every other week, in 8 weeks (2 month) four sessions of OPU-IVF are performed, and finally 24 viable embryos are produced.
In multiple ovulation and embryo transfer (MOET) program which the donor is superovulated, fertilization by AI, and embryos are flushed from the donors, the cycle is 60 days, about 6 viable embryos are flushed from one donor per flush.
As summary, the yearly embryo yield by OPU-IVF program is 144 while it is only 36 in vivo embryos produced by MOET. Thus OPU-IVF is more effective than MOET in embryo production.
The Economic Advantage of OPU-IVF Program
OPU-IVF has many advantages over MOET program if it is working well. There include
(1). Producing more embryos than that in MOET for valuable donors. OPU-IVF can produce 144
embryos per donor per year, while MOET produces 36 embryos per donor per year.
(2). The donors that are not successful in conventional MOET can be used for OPU-IVF. The valuable donors tend to make unfertilized eggs or degenerated embryos due to reproductive problems.
(3). Open cows, pregnant cows, heifers and heifers prior to sexual maturity (such as 8-10 month old) can be used for OPU-IVF.
(4). Fewer semen are used to produce each embryo with OPU-IVF vs. MOET, and reverse sorted semen can be used to fertilize oocytes that generate sex desired embryos for ET while it is not very successful in MOET.