Apr 1, 2013

Just another day on the farm with ET

Our friends raise cattle and this is prime-time calving season. We took a trip out to their farm not only to see the baby calves but to watch some of next year’s baby calves get their start. Dr. Thompson, an area Embryologist, was at the farm and flushing embryos out of several of their cows while we were visiting. I am always up for a learning experience and this was a fascinating one.

kids and a shorthorn cow having embryos flushed
On our farm, all of our sheep are bred the old fashioned way. In fact we just turned our three rams out into the field for fall lambing. In the cattle business things are a bit more high tech using AI (artificial insemination) and ET (embryo transfer). ET is not a new practice. In fact, it dates back to the 1890s in rabbits, sheep and goats in the 1930s and cattle in the 1950s. The practice in beef cattle really took off in the 1970s in the U.S. and has been an increasing part of cattle operations ever since.

Why ET? It is pretty basic — to improve genetic selection by increasing the number of progeny from females that are either proven or perceived to be of great quality. ET also allows a breeder to generate more offspring from rare and valuable semen.

Dr. Thompson, a local embryologist, has been working in this field for a long time. This is not an easy or glamorous profession, but it is something he has mastered by developing a great success rate of retrieving quality eggs. Retrieving quality eggs is all about cow maintenance and making sure she has the proper nutrition and care to ensure the best success rate. This process is expensive and time consuming, but can lead to great genetics to better the breed even after the cow is past her ovulating prime.
Between days 6 and 8 after the cow has been inseminated, the embryo recovery is done. The cow is placed in the cattle shoot for her protection and the safety of Dr. Thompson. This entire process is done quietly and without stress to the cow. In fact, these cows knew just what to do. They even posed for photos with the children during the process and walked right out of the shoot and into the pasture. The cow receives an epidural block at the tail head to prevent straining and to make the job a little easier.

A flexible rubber tube catheter is passed through the cervix and into the uterus. The cuff is inflated with a saline solution to hold the catheter in place and to prevent back flow of fluids. Saline solution is flushed-filled and the uterine horn is gently massaged and the fluid containing the embryos is drawn back out through the catheter. This solution is collected through a filter and into a cylinder or dish.
rubber tube catheter
saline solution and collection dish
You cannot see with the naked eye any of the eggs. They are microscopic. This process takes about 20 minutes and the eggs must be kept at room temperature. This can be particularly tricky on a 30-degree day in March. The dish with (hopefully) quality embryos is placed in the truck to be kept warm until we made it in the house to set up the mini laboratory.

The egg dish is looked at under the microscope and all the eggs are removed and placed into a separate dish. At this point, Dr. Thompson is evaluating the eggs and giving them each a rating of 1, 2 or 3. The embryos are then placed into straws, with each egg in a separate straw. Under the microscope you could see the little placenta already beginning to form. Eggs rated 1 or 2 (excellent and good) will be frozen and eggs with a 3 rating would be implanted in donor cows (cows on the farm not for their great breed quality but because they are good mothers to carry and raise the baby calves) immediately. Grade 3 embryos are still good, but they just would not survive the freezing process.

Dr. Thompson rating embryos
embryos freezing
canes straws with embryos will be placed in
Each straw is then placed in an embryo freezer using ethylene glycol to freeze. This process takes about an hour to completely freeze the eggs. It’s a gradual process that has to be done just right to ensure the best egg quality and longevity. The eggs are placed in a cane that is labeled with the cow and bull’s information and are ready for the storage tank. The eggs will remain there until it is time to implant them in the next round of cows.  In this case some of the embryos will be implanted in May for next year’s baby calves. Some of the embryos will be sold in sales and other will be kept for a long time to use when desired. If stored and collected properly embryos can be kept indefinitely.
embryo storage tank

While this process was fascinating to watch and learn about, it really is just another day on the farm for the cattle producers and Dr. Thompson.

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