In vitro fertilization (IVF) technology and processes have rapidly evolved over the years, making this reproductive technology an economically beneficial practice for farms of all types and sizes.
As a result, embryos continue to play an increasingly important role in dairy cattle reproduction. In fact, the annual production of transferable bovine embryos nearly doubled between 2009 and 2021.
According to the International Embryo Technology Society, the expansion in embryo transfer use, likely associated with emerging market niches, is leading to an increase in total embryo numbers. And, interestingly, cryopreserved (frozen) embryos now account for nearly half (49.1%) of all cattle embryos transferred worldwide.
Dairies that rely on embryo transfer often achieve success rates similar to artificial insemination (A.I.). Plus, in times of heat stress, pregnancies resulting from embryo transfer may exceed those of A.I., with some dairies reporting pregnancy rates as much as 10 or more percentage points higher for embryos.
Yet, positive outcomes are not possible without a commitment to quality – of embryos and transfer techniques.
Quality first, last and always
Embryo quality drives success.
Researchers at the University of Illinois found that approximately 80% of the roughly 1.5 million bovine embryos transferred in 2021 were produced in vitro. Yet not all procedures result in pregnancy, let alone a live calf. The studies found that 73% of pregnancy failures following implantation are partly due to transferring poor-quality embryos.
Strict quality protocols are critical to embryo recovery, fertilization and storage. If you are not sure about the grade of the embryos you invest in, or have questions about protocols, ask. Reputable reproductive organizations willingly share this information.
Each embryo is graded on a scale from 1 to 4 based on embryo quality and appearance. The International Embryo Transfer Society developed this system to help define embryo quality:
- 1 is classified as excellent.
- 2 is classified as good.
- 3 is classified as fair.
- 4 is classified as dead or degenerated.
Not surprisingly, studies report that the highest rate of conception in recipient cattle following embryo transfer occurs with the transfer of embryos classified as excellent and good.
Purchasing embryos that are of excellent quality can aid in creating a profitable pregnancy.
Bypass heat stress
Embryo quality also factors into pregnancy rates during times of heat stress. That’s because higher temperatures have a negative impact on a cow’s oocyte quality and subsequent embryo formation and quality.
Incorporating embryo transfer technology offers dairies opportunities to offset reproductive challenges when temperatures rise because you are transferring a high-quality day 7 embryo.
Additional research suggests fertilization failure is generally underestimated in cows undergoing heat stress.
For example, when single-ovulated cows were flushed six days after A.I., researchers noted that the fertilization rate went from about 90% in cooler months to about 50% in warmer months. Also, high environmental temperatures reduce the rate at which embryos develop. At the same time, embryos three or more days after conception are less sensitive to heat stress.
As a result, embryo transfer increases pregnancy rate during periods of heat stress by allowing embryos to bypass the period when they are most sensitive to elevated temperature – the first two days after breeding.
Find success for repeat breeders
High-quality embryos and embryo transfer technology also help overcome infertility in repeat breeders.
Generally, the repeat breeder scenario is caused by two main factors: failure of fertilization or early embryo death caused by poor-quality oocytes and an inadequate uterine environment. Of the two, poor oocyte quality appears to be the bigger infertility culprit. The incidence of repeat breeders in the U.S. has been reported to be as high as 24%.
Embryo transfer has the capability to minimize the effects of poor oocyte quality and unfavorable uterine environments on early embryo development during the first seven days after ovulation in repeat breeder cows.
Several studies showed embryo transfer significantly improved the pregnancy rate in this group of animals. For instance, one study showed pregnancy rates for repeat breeder Holstein cows were greater after embryo transfer (41.7%) than after A.I. (17.9%).
As reproductive programs evolve, and with successes like these in overcoming reproductive challenges, it is apparent embryo transfer has a place in protocols for many herds.
Plan for embryo transfer success
Lastly, remember the next time you transfer embryos, pregnancy rates depend on the quality of the embryos before freezing, the ability of the person freezing the embryos, the storage practices, the quality and preparation of the recipients and the skill of the person performing the transfers.
Use these six tips to help ensure embryo transfer success.
- Invest in excellent-quality, 1-rated embryos.
- Choose optimal embryo transfer recipients.
- Maximize estrus synchrony between the recipient and the age of the embryo.
- Properly thaw and handle embryos.
- Use proper transfer technique.
- Take your time.
Embryo transfer is an exacting procedure, meaning proper technician training is essential. Allowances must be made in breeding programs to ensure and maintain technician proficiency. Additionally, embryo transfer can be a more time-consuming process than insemination. Adopting this reproductive tool often requires a shift in mindset and employee resources to achieve optimal results and take advantage of embryo quality.
References omitted but are available upon request by sending an email to the editor.
