A Chain is Only as Strong as its Weakest Link
contributed article by Dr. Vince Collison, Collison Embryo and Veterinary Services,
Rockwell City, Iowa

When I’m asked about how we can have the greatest success with an embryo transfer (ET) program, I often respond with the statement: “A chain is only as strong as it’s weakest link”.
As we start the season for transferring embryos into beef cattle for next year’s calving, it’s a good time to review what we can do to help maximize success on embryo transfer day. Embryo transfer is a complex chain of events and recipients, embryos, facilities, and technicians all play a part in the outcome. Any weak links in the chain and results can breakdown quickly.
Recipients:
• This is probably the most important part in the success of an ET program. Try to eliminate cows from the transfer group that have a history of poor fertility.
• Have recipients in good body condition. Also, try to eliminate cows with histories of poor mothering ability, poor milk, and poor dispositions.
• Perform all vaccinations at least 30 days before estrus synchronization will start. Especially when using modified live vaccines for pre-breeding.
• If purchasing cows for recipients, try to procure them at least 45 days before the planned transfer date. It will take this long to get the cow vaccinated ahead of time. It also allows the cows to settle into their new environment. It will take some time to adapt to a new herd and for their immune system to stabilize with the new herd. It also allows you some time to find any issues on any of the new cows that may need addressed or cause them to be culled before receiving an embryo.
• I wrote an article for the November 2024 issue that covers a lot of what makes a good recipient. Refer to this article if you are going to be acquiring new recipients.
• Have the nutrition right for the recipient cow, before and after transfers. How the recipient is fed plays a large role in the fetal programing (epigenomics) of the developing embryo. What happens now with recipient nutrition can affect the calf for life and even carry on for the future generations that this embryo calf will produce.
• Make sure the energy level in the ration is high enough that the cow is gaining body condition, especially for recipients that are younger and nursing calves. On the other hand, don’t feed them into a state of obesity. Cows that are obese can have reduced fertility. I would rather have a greener cow that is gaining weight for a recipient, than a cow that is over fat and trying to lose weight.
• Keep the recipients on a good trace mineral program prior to calving and throughout the breeding season. I’m a fan of having some mineral chelate in the mineral product. Chelated mineral will absorb better.
• Provide recipients with plenty of shade and access to fresh water. During the hot summer months, access to shade can help to improve pregnancy rates and reduce early embryonic loss.
Facilities:
• Have the working facilities under roof if possible, or at least have the area where embryos are thawed and handled under a shaded area that is protected from direct sunlight.
• Have a squeeze chute with a palp cage that shuts securely to prevent cattle in the alley behind the chute from pushing through while working. Also, a palp cage that is big enough to work comfortably behind the cow.
• Pens that allow for easy sorting and low stress handling of the cows.
• Set up so that there is minimal activity out in front of the headgate while performing transfers so the recipients will stay calm.
• Have enough help to efficiently move cattle through the working system with minimal stress.
Embryo Handling:
• I would start this section by saying that how embryos are handled is super critical to success. I’ve seen many producers expose embryos in the neck of the tank longer than they should while trying to locate embryos. The neck of the tank is -80°C and thaw damage can start to occur at temperatures over -130°C.
• Keep the area for thawing and loading embryos protected from direct sunlight.
• Have the thawing area protected from wind. Many technicians will work with embryos in a nitrogen filled dewar while thawing. Protection from wind keeps the nitrogen from burning off so fast and helps to keep the thawing process more consistent.
• If you are storing your own embryos, keep canes containing embryos down below the neck of the tank as much as possible. Embryos are more prone to thaw damage than semen. We like to use a flashlight to locate the cane we want to pull while it is down in the body of the tank so as to minimize the amount of time the canister spends in the neck of the tank.
• When receiving embryos from a shipment, pour some nitrogen into the dry vapor shipper before moving embryos from the shipping tank to the regular nitrogen storage tank. This keeps the goblets on the cane full of nitrogen and protects the embryos during the move between tanks.
• Work to line the stage of the embryo up with the synchrony of the recipient. When transferring embryos into a group of recipients, it’s nice to make sure that stage seven embryos are going into cows that showed heat eight days prior as much as possible. This is probably even more important when transferring IVF embryos.
• If storing your own embryos, try to have the records of embryo inventory available on transfer day. This makes it easier to locate the embryos if we can know the cane codes. Also, this paperwork will have the stage and grade of each individual embryo. This will make it easier to plan which embryos go into recipients based on when they came into heat. If you receive any shipments of embryos, there should always be some paperwork that is included that shows all of this information.
Technicians:
• In many embryo sales they will often guarantee a certain pregnancy rate if embryos are transferred by a certified technician. AETA certification is a program administered by the American Embryo Transfer Association. To be certified, a DVM or Ph.D. in animal reproduction has to pass an eight-part exam. In addition, they have to provide documentation of a certain volume of work performed in the last year along with several client references. While many proficient technicians are not certified, this program ensures a certain level of competence.
Lastly, remember ET is a process where details make the difference.
learn more www.collisonembryoservices.com
Dr. Vince Collison is co-owner of Collison Embryo and Veterinary Services PAC
in Rockwell City, Iowa.
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