Genetics set the potential for the upper and lower levels of production limits an animal can achieve. Advanced reproductive technologies such as in vitro fertilization (IVF) can help propel herd genetics to the next level, multiplying the success of breeding programs in a short amount of time, ultimately leading to increased profitability.
“The average cow will only produce a few, if any, female offspring in her natural lifetime. IVF programs can potentially allow for one genetically superior cow to produce 10 to 25 female calves within one year,” says Dr. Charles Looney of OvaGenix, a biotechnical company specializing in cattle breeding, based in Bryan, Texas.
Looney and his team produced the world’s first cloned cow, the first transgenic cloned cow and the first commercial oocyte retrieval and IVF programs.
What is IVF?
Most producers are familiar with the embryo transfer process. “IVF is almost identical to an embryo transfer; the only difference is in the embryo flushing method,” says Looney. It is a slightly more complex process where a veterinarian uses an ultrasound-guided needle to aspirate follicles off of a cow’s ovary through the vaginal wall.
A vacuum system with a searchable filter is used to recover the contents of each follicle, including the important oocyte or unfertilized egg. Once collected from the cow’s ovaries, the filter is taken to a lab, where it is rinsed and searched for oocytes with a microscope. The oocytes are then retrieved, counted and graded.
The recovered oocytes are placed into a special media designed to mimic the cow’s uterine environment, including temperature and pH. This allows them to mature for 24 hours. The next day, the oocytes are fertilized with semen and the resulting embryos are placed in an incubator for an additional seven days to mature.
Embryos can then be evaluated and quality-graded, and grade one and two embryos are transferred into recipient animals that are seven to eight days post-heat, similar to conventional embryo transfer programs or vitrified, the freezing method used for IVF embryos for transfer at a later date.
The very first IVF procedure was done at the University of Georgia in 1981, and the method was perfected over the years using ovaries from slaughtered cattle. IVF struggled to establish itself as a legitimate technology because of low embryo production and pregnancy rates, making it unaffordable for most producers.
It was often only used as a last resort for cows that could not produce offspring in any other way. With increased technology, today IVF is a practical and competitive reproductive tool with several applications.
“IVF gives producers a wider range of options than embryo transfers. Since follicles grow from the time of birth and are even viable recently after death, it gives producers more options in when and which cows they can collect from,” says Looney.
What are the advantages of IVF?
IVF offers several advantages to producers over traditional embryo transfer programs, with the potential of a large variety of calves on the ground in a year.
Donor IVF aspirations can be performed every two weeks, and semen from different bulls can be used to fertilize each of the oocytes from each collection, allowing for the opportunity for greater genetic diversity resulting from one cow.
Embryo transfers result in five to six embryos each collection, which can only be done every 60 days. IVF collections result in approximately 20 oocytes per aspiration and, on average, 30 percent develop into viable embryos, resulting in four to five grade one and two embryos per collection.
Aggressive IVF programs can result in more than 50 calves produced from one cow within a year. This is double the calf production achieved in conventional embryo transfer programs.
Producers are able to start their donors on IVF programs as virgin heifers at the age of 10 months old. Additionally, since IVF does not involve the uterus, pregnant donors can still be collected throughout the first trimester of pregnancy, until day 100 to 120 of pregnancy, allowing producers to breed genetically valuable donors on time while still capitalizing on creating additional offspring.
Donor cows that have been unable to achieve success with embryo transfers due to blockages, scarring, uterine infections, impassable cervices, overstimulation or because they make unfertilized or degenerate embryos are also good candidates for IVF.
Embryo transfers often require the use of two to three straws of semen to fertilize the egg. Since oocytes in an IVF session are fertilized in a microscopically controlled environment, significantly less semen is needed. One straw of semen can be used on the recovered oocytes from up to 12 or more donors, allowing producers to make the most of rare or expensive semen.
IVF also has an advantage in that it can be done with fewer amounts of hormone shots and can even be performed unstimulated. It is not necessary to superovulate cows, nor is it necessary to synchronize them. This is a major breakthrough since the donor cows are not exposed to hormones that might compromise the reproductive soundness of the animals, and they can be worked without prior preparation time for the procedure.
What are the disadvantages of IVF?
“Obviously, the best environment to develop bovine embryos is within the uterus of the cow. We have not yet developed a compatible system,” says Looney. Embryos developed in a lab are not as hearty, which results in lower pregnancy rates and compromises freezability.
“The field is in the process of learning how to produce embryos for a wide class of cows faster and at a higher success rate. IVF was developed in the animal science realm of reproductive physiology, and some vet schools are not yet teaching the procedure,” he says.
IVF embryos transferred fresh yield, on average, a 50 percent pregnancy rate in well-managed recipients. This rate is slightly reduced with frozen IVF embryos. Studies have shown that embryo transfer leads to a slightly higher pregnancy rate, with 7 percent advantage on fresh embryos and a 10 percent advantage on frozen embryos.
It has been shown that conception rates for embryos in cows during times of heat stress are better than traditional breeding. Transferring frozen embryos from conventional flushing during times of heat stress may help improve conception rates during the times it is hardest to get cows to settle.
Follicle aspirations are an invasive procedure that can cause bleeding and infection, which can create ovarian adhesions and requires a highly skilled veterinarian to perform.
Not all donors will produce viable embryos; 10 to 15 percent of IVF procedures will result in no viable embryos.
Some instances of large offspring syndrome, where calves are born abnormally large, have also occurred. While rare, they are generally correlated with matings where extreme birthweights are expected.
Is IVF economical?
It’s no secret that IVF technology can get expensive, with costs that typically double that of embryo transfer. However, the costs need to be analyzed on a long-term basis with costs offset by the overall long-term improvement of the herd. While the cost of the procedure is higher than embryo transfer, the actual cost per embryo is often lower.
“While it may be more expensive, it gives producers many more options,” says Looney.
IVF programs allow for the greatest genetic progress in the shortest amount of time. Decreasing generation intervals serve to improve the genetic base of the herd.
No matter what your formula is for defining a “genetically valuable cow,” the genetic basis of your herd improves with your selection intensity, defining what is important on your program.
“Some breeders are using IVF to maximize the impact of their very best cows or to rapidly increase herd sizes; for these purposes, IVF is a powerful tool. IVF is not for everyone or every cow, but more and more cattlemen are realizing that it has the potential to do things never thought possible before with other reproductive technologies,” says Looney. 
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Jennifer Archibald
- Freelance Writer
- Lodgepole, South Dakota
- Email Jennifer Archibald
