EMBRYO TRANSFER

RECIPIENTS

Selection of recipients is one of the most important aspects of any ET program. In most cases the implanting of embryos involves a financially valuable genetic material that, in order to have a successful program, is required to have good quality, well managed recipients. Estrous synchronization protocols are very useful but they cannot replace good management. Feeding and vaccination protocols are very important areas that often are neglected.

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1. Selection:

   1. Cows 3 to 8 years old make good recipients once they have a good calving record. Cows will be better suited when transferring embryos of relatively high birth weights. In general, cows have more milk than heifers, an important factor to consider when they have to raise an embryo calf.

   2. Heifers are good recipients providing they’ve reached their breeding weight (around 65-70% of mature weight) and are cycling. Avoid embryos with large EPD’s for birth weights in heifers.

   3. 1st calvers are still growing and are under more stress than the rest of the herd due to the fact that they have to raise a calf.  For these reasons 1st calvers can be difficult to get pregnant, if they are under intensive management and receiving enough good quality feed they can be used as recipients.

   4. Use fertile animals.  Cows with calves at foot that have no history of calving problems, and are open not because they fail to conceive by AI or natural breeding, make good recipients. Retain animals successfully used previously as recipients. Do not use recipients that have been prepared unsuccessful twice before.

   5. Animals with temperament problems should be removed from the program.

   6. Select animals that maintain or are gaining body condition, an ideal score of 2.5-3 is preferred at the time of transferring the embryos.

2.  Management:

1. Cows need to be at least 60 days post-calving, when possible, it is recommended to wait a little longer (75-80 days).

2. Recipients need to be adapted and kept on the same feeding program for 6 weeks before getting implanted and 8 weeks after. It is not advisable to move recipients from a dry lot to a pasture with lush grass immediately after implanting. If for some reason feed needs to be changed, do it gradually over a period of 4 weeks. Keep recipients under the same management conditions for as long as possible.

3. Administer Vitamin A, D and E and mineral supplementation at least 4-6 weeks prior to implanting.

4. Recipient identification is essential, tags must be easy to read and whenever possible put tags in both ears.

5. Vaccination protocols must be up to date, pay special attention when vaccinating recipients and/or calves nursing recipients with modified live vaccines for BVD and IBR. Do not vaccinate 40 days prior to the implanting date. Consult with your veterinarian if some modifications need to be made to the vaccination protocols.

6. Do pregnancy diagnosis on every recipient before getting them in an ET program.

7. We do not recommend AI for recipients that show heat after receiving an embryo, there is a chance that some of these cows are pregnant. Using a bull is safest.

8. Move recipients slowly and keep them calm at all times while they are getting used to the handling system.

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3.  Preparing Recipients:

1. Embryos are implanted 6 to 8 days after recipients have had a heat, we can implant embryos in cows that have either natural or synchronized heats. For practical purposes, most of the time recipients get synchronized to implant embryos on a determined date; many times they are prepared to coincide with the flushing of the donors.

2. There are many different protocols used to synchronize estrus (heats) in recipient cows, each with certain advantages to it. These protocols require the use of drugs such as prostaglandins (Estrumate, Lutalyse), GnRH (Fertiline, Cystorelin, Factrel) and progesterone (CIDR).

3. How to apply CIDRs (please see our articles section for complete instructions). It is recommended to rinse and disinfect your CIDR applicator between cows.

4. See image below for typical synchronization protocol for recipients.

5. The use of recipients can be optimized by performing an early pregnancy diagnosis around 21 to 23 days after being implanted. Cows that show heat around 14 days after being implanted can be tested by ultrasound and re-implanted 7 days later if they are open. Cows that did not show heat can be “preg checked” and the open ones can be re-synchronized immediately to be implanted in 16 days. It is not recommended to use cows as recipients if they do not get pregnant after a second implant.

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4.  Implanting Day:

1. There are minimum requirements for handling facilities when implanting recipients, most squeeze chutes work fine for this purpose. We should be able to place a pole behind the animals since in many cases recipients stand better without catching their heads.

2. Recipients receive a sedative (Acepromazine maleate) a few minutes before getting implanted, while waiting behind in the chute. The use of “Ace” allows working with less risk of damage or injury to the cows and personnel, recipients should move smoothly as they get into the squeeze and stay calm.

3. All recipients get an epidural just before getting implanted and they must be herded slowly right after.

4. Depending on the program used, it may be required to have the heats and breeding records on hand the day of implanting the embryos.

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Never hesitate to contact us with any problems or questions about the program. Communication is vital.