DNA Profiling: The Basics

by Matt Barten, Embruon

A BRIEF REVIEW OF BOVINE EMBRYO BIOPSY

Bovine embryo transfer is a broad term used to define the production and transfer or freezing of bovine embryos. This process gained traction in the late 1970s to early 1980s as a commercially viable option for beef and dairy producers to take advantage of their best genetics. Over time, the embryo transfer (ET) industry has evolved in many ways. Examples of this would be the advent of freezing embryos, synchronization protocols, as well as in-vitro fertilization (IVF). Another such evolution was realized with embryo biopsy, and when coupled with today’s powerful advancements in genomics has the potential to be another milestone within the industry.

THE PROCESS OF BOVINE EMBRYO BIOPSY

Embryo biopsy allows producers to gain insight of the genetic characteristics of a developing embryo. This has been a remarkable achievement. The process of bovine embryo biopsy can trace its beginnings to the early 1990s. Initially, it was used to determine the gender of an embryo prior to transfer. This was particularly attractive for the dairy industry in utilizing ET. Technological advancements in the realm of DNA amplification and sequencing now allow producers who utilize this technology to know not just the gender of an embryo but, also, its genomic profile, or genomic-enhanced expected progeny difference (GE-EPD), prior to freezing or transfer. The widely-accepted method for embryo biopsy is to perform it on a more advanced stage embryo, usually a morula to expanded blastocyst. Cells from the region of the embryo destined to become the placenta are removed, or biopsied, from the embryo and collected for processing at a lab. In several ways we, at Embruon, have adapted our biopsy process to mimic that found in IVF. Doing this allows us to be more “embryo centric” in our approach and biopsy embryos when the time is right for them. We send all samples to GeneSeek in Lincoln, Nebraska. They are the largest genomics lab in the world, processing about 8,000 samples per day. Via their pipeline, we can generate information from the biopsy as it pertains to gender, recessive status, and a full genomic profile or GE-EPD for an individual embryo. In this way producers can make defined genetic decisions about embryos they will transfer earlier than ever before.

AFTER THE BIOPSY

Our post-biopsy process gives embryos some needed time to relax before moving on to the next step. We then observe every embryo to verify it exhibits the characteristics of health. Many of the embryos we work with are then frozen at which time they are ready for shipment back to the client. Once the biopsy has been successfully transferred to the lab it must be processed in a very specific way. Inherent with embryo biopsy is the fact that there is very little genetic material in its present form. Because of this, GeneSeek must amplify the DNA they receive to create enough to be of use in their lab. I often use the illustration of a bushel basket of corn being turned into two semi-trailer loads of corn. The amount of time the lab needs to derive information for the producer depends on how much information is wanted. Gender determination can be accomplished in one day while a GE-EPD will take three weeks. Once results are generated at the lab, producers can use the information to determine which embryos will best fit their program and which ones would not. Transfer of embryos to a recipient should be performed by a licensed ET practitioner using the same protocol as non-biopsied embryos. Literature shows one can expect as much as a 10-percentage-point drop in conception for biopsied embryos.

WHAT IS THE VALUE?

One of the major impediments to genetic gain within the beef industry is the long generation interval or the average age of the parents when the offspring are born. As it pertains to bovine ET, we need to, also, consider the opportunity cost associated with every recipient. Using embryo biopsy as a reproductive management tool, producers can essentially make decision at less than nine months. Imagine looking through your inventory of embryos utilizing the same genomic information that would be found in a semen catalog. How much easier would it be to decide in an inventory of 700 embryos which ones to transfer in a 500-head recipient operation. Or utilizing more of your male-embryo population to calve in sync with a spring bull sale and the female population to calve in sync with a fall female sale. Ensuring recipients carry only embryos a producer knows fit their specific program can be accomplished with this technology. Further, economically for the recipient, the drop of conception associated with biopsied embryos is more than made up for by not transferring embryos that would not fit some producers’ endpoint goal genetically. Over time, this, also, speeds up genetic gain within a breeding program.

WHERE FROM HERE?

Embryo biopsy should be viewed as another tool producers can incorporate in their reproduction program. Combining embryo biopsy with the technological advancements in genomics has many broad reaching applications within the beef industry. The use of genomics to decrease generation interval and drive intensity of selection is seen in other protein markets as well as the crop production industry. In the future, it may be possible for commercial application of this technology in an IVF lab. It is a model that human IVF has proven can be accomplished and viable.