Comparing Conventional Embryo Production and In Vitro Fertilization(IVF) as a Means to Propagate Superior Genetics in your Beef Herd

Justin R. Kristjansson, DVM

For almost 50 years beef producers in Canada have been utilizing embryo transfer technologies to multiply superior genetics within their herds, and their breeds. With the importation and increase in popularity of the Continental beef breeds in the 1970s came a demand for the genetics that surpassed the availability of live

and required time for the donor and recipient to heal along with an increased risk of post-operative complications.

Early surgical embryo recovery and transfer techniques have since been replaced by non-surgical transcervical procedures now known as “conventional flushing”. In a conventional flush, the donor dam is subjected to a hormone synchronization protocol that results in her ovulating multiple oocytes (eggs) into her uterus that are then fertilized via artificial insemination. The donor dam incubates the developing embryos for seven days, and on day seven a catheter is placed into the uterus of the donor dam and the uterus flushed out with specialized fluid media that allows for the recovery and survival of the embryos.

cattle in Canada at the time. Veterinarians and researchers, in various places in the world including Canada, were developing protocols to produce multiple embryos from elite females, to recover them intact from the donor dam’s uterus, and transplant them individually into the uterus of recipient dams. Conventional flush protocols result in an average of seven, Grade 1 embryos per collection. The number of embryos varies considerably based on each individual donor dam’s response to the hormone treatment protocol, ranging from a low of 0 to highs in the 20s and 30s.

Early techniques to recover embryos from the uterus of the donor dam and transplant to the uterus of a recipient dam involved surgical procedures for both cows. While embryo production rates, and subsequent pregnancy rates of transplanted embryos were generally quite good, surgical procedures greatly increased the time required to perform the embryo recovery and transplant, In recent years In Vitro Fertilization (IVF) has arisen as another means of embryo production from high genetic value females. In Vitro is Latin for in the glass, as every step of embryo production after oocyte collection occurs in a laboratory, not in the living animal (in vivo).

encompass what is actually four individual steps in embryo production: i) Oocyte Pick Up (OPU) - The donor dam is super-stimulated with follicle stimulating hormone (FSH) similar to a conventional flush protocol, though a CIDR or her pregnancy prevent her from ovulating those oocytes. Those oocytes are collected into a filter with an ultrasound-guided needle on a vacuum pump, and the oocytes are searched and graded under a stereomicroscope. ii) In-Vitro Maturation (IVM)- The oocytes are placed in specialized maturation media for 24 hours that simulates the natural process and environment of ovulation, thereby readying the oocytes for fertilization. iii) In-Vitro Fertilization (IVF)- The extender and dead sperm are removed from thawed semen and the sperm are placed with the mature oocytes for 24 hours. One straw of semen can potentially be used to fertilize oocytes from three to five cows individually, or the oocytes can be pooled together at maturation/fertilization to decrease the costs of IVF. Frozen semen can also be Reverse-Sorted (sexed) at this stage to select for either bulls or heifers. iv) In-Vitro Culture (IVC)- The now fertilized oocytes are kept in specialized culture media and allowed to grow and develop for six days. At the end of the culture the embryos can be implanted fresh or frozen and stored the same as conventionally produced embryos.

On average, beef IVF donors produce 20 oocytes per OPU with an average of six, Grade 1 embryos produced from those oocytes. This 30-35% embryo development rate varies considerably on an individual donor basis, with some donors producing fewer oocytes but with a higher embryo development rate, while other donors may produce higher than average oocyte numbers with poorer embryo development rate. The best IVF donors achieve embryo development rates of over 50% of the total oocytes started with, approximately 25% of donors fall into this category with approximately 3% of all donors achieving embryo development rates greater than 75%.

The benefits of utilizing IVF to produce embryos from your high genetic value females are numerous. While many prospective donors may not work in a conventional embryo flush program, they may work quite well in IVF production. However, there are some prospective donor cows that simply do not produce in either system, and unfortunately there is no ‘miracle cure’ to produce embryos from some cows. Other benefits of IVF include being able to produce embryos from donors while they’re pregnant, producing embryos from young heifers pre-breeding to shorten generation intervals and maximize genetic gains, maximizing the use of rare or expensive semen on multiple donors at once, and the ability to collect donors every two weeks. The short interval needed between IVF collections means that more embryos can be produced from a donor in a shorter amount of time than is possible with conventional flushing, allowing producers to maximize the numbers of embryos banked or implanted in a short breeding season. Embryo transfer pregnancy rates for Grade 1 IVF embryos are now virtually identical to that of conventionally produced embryos, with the most variability coming from the management of the recipient herd. ...cont’d

16 embryos developed via the IVF process.

Nine embryos gathered from the conventional process.

No matter which embryo production system is used to produce the embryos, embryo transfer is the most effective way to maximize the positive influence of the elite genetics in your herd. Producing a high number of calves from elite dams allows numerous full and half sibling females to be retained, creating a more uniform and consistent herd, and marketing a uniform bull pen that customers appreciate to find consistency year over year. The opportunity to introduce genetics to your herd through embryo transfer is a great way to access elite genetics from other breeders or countries that may not be available, or affordable, as live purchases. These genetic introductions can build a foundation of success for your own herd for years to come and allow you to realize your own genetic improvement goals for your herd.

For more information on embryo transfer, in vitro fertilization, and success in achieving your herds genetic goals please visit bowvalleygenetics.com

Justin Kristjansson is a veterinarian and the Assistant Manager at Bow Valley Genetics Ltd. Located near Brooks, AB, as well as a member of XLVets Canada.