A technology that is starting to be more commonly used in beef cattle to mass produce outstanding genetics is In Vitro Fertilization (IVF). This allows producers to harvest, fertilize, and make embryos on an operation’s top females throughout a wide range of their reproductive status.
Although the process works best on reproductively-sound females, it can also be done on pre-pubertal heifers, as well as on cows that are pregnant, won’t respond to flushing, are old, or have problems with their oviduct or uterus. This means more calves can be produced during the lifetime of a donor, starting at approximately 7 months of age on through past a cow’s normal reproductive lifespan.
When discussing the benefits of IVF in beef cattle, Bruno Sanches, chief operating officer of the IVF company, Vytelle, says, “It is a no-brainer for seedstock producers looking to multiply the genetics from their best donors. It allows managers to mass produce these top genetics and shorten the generation interval, which increases the rate of improvement.”
One of the major advantages of IVF is that it can be performed on pregnant donors during approximately 30-100 days of pregnancy. This keeps donors in production and at optimum body condition score, avoiding the “stale donor cow syndrome” sometimes seen when females are taken out of production for normal embryo transfer.
Speaking to this, Dr. Shantille Kruse of Boviteq—a company that has been in the embryo transfer business since the early 1990s and doing IVF in North America for approximately 20 years—relates that donors in an IVF program can be maintained in an ideal body condition score of 6. She reports that when donor cows get too fat, it affects the number and quality of fertilized embryos that can ultimately be produced.
How it works
Most companies like Boviteq have donors kept in highly-specialized centralized facilities for collection. The process typically is done every two weeks. Cattle are given hormones (CIDRs and Follicle Stimulating Hormone, FSH) and then oocytes—unfertilized eggs—are harvested from the various follicles on the ovaries. A needle is used to aspirate and harvest the oocytes, which is guided with the aid of ultrasound. The number of oocytes collected per session varies widely, but producers can expect approximately 18 in a typical session.
They are then identified and washed in a Petri dish, and then fertilized 24 hours after collection. One straw of semen can be used to fertilize large numbers of oocytes from multiple donors, which allows for the optimum use of very expensive and rare semen. The embryos are then allowed to mature for seven days, at which time they can be implanted into recipient females fresh or frozen for later use. The industry standard is approximately one-third of the oocytes will become Grade 1 fertilized embryos.
The media used to culture the new embryos in for seven days varies by company. Originally, the industry standard was to use fetal bovine serum, but various problems can arise with this component in the medium. That is why Vytelle—a relatively new company to IVF in the U.S.—and Boviteq utilize proprietary synthetic media to culture the embryos.
There are pros and cons to various companies’ models. Bringing cows to centralized and satellite locations allows for high use of investment in the specialized equipment and personnel, and Kruse feels the hormonal regimen allows them to aspirate more follicles and optimum oocytes.
She says, “The FSH mimics what the cow would do when she ovulates, so is more likely to produce a good quality oocyte that will result in a transferable embryo and ultimately pregnancy.”
In contrast, Vytelle’s model has the advantage of collecting oocytes on producers’ farms or ranches. They do not use the hormonal regimen, which allows them to collect donors weekly instead of every two weeks.
Sanches says, “The number of oocytes is similar to donors given the hormonal regime, and the weekly collection results in more total high-grade embryos produced in a short period of time.”
Sanches also touts that their system is more natural, working with a cow’s normal hormonal system. He does say that without the hormone regimen, the follicles are less pronounced, which requires their technicians to use the highest-end ultrasound equipment and smaller, thinner needles to harvest the oocytes.
Vytelle also feels their media results in higher livability of the embryos and eventual fetuses. According to Sanches, “We feel our process increases pregnancy rate and decreases embryonic death loss. In the end, customers are looking for live, healthy calves on the ground.”
IVF is a technology whose time appears to have come of age. It is already widely used in the dairy industry where managers only want to produce replacement heifers from their best females. It allows dairies to turn generations as never before, and allows them to make maximum use of genomics. Lower-quality cows genetically can then be bred to beef bulls to produce value-added steers.
This kind of specialization can be foreseen in the beef industry. As genetic analysis becomes more comprehensive to cover not only production traits, but also economically-important traits like soundness and disease resistance, the possibilities to produce only the best genetics in mass for replacement females becomes possible. It can also lead to production of sires that will suit a variety of needs both for seedstock and commercial purposes. It is certainly an exciting time in the industry as technology such as IVF continues to leap frog forward. — Dr. Bob Hough, WLJ Correspondent