Recipient Protocols for Synchronization, Timed ET and Resynchronization
by Barb Baylor Anderson for Angus Productions Inc.
NASHVILLE, TENN. (Aug. 6, 2010) — Edwin Robertson, veterinarian with Harrogate Genetics International, Harrogate, Tenn., said there is "more than one way to skin a cat" when it comes to the availability of successful recipient protocols for synchronization, timed embryo transfer (ET) and resynchronization. The key to success, he told attendees of the Applied Reproductive Strategies in Beef Cattle (ARSBC) Conference, is to get familiar with the protocol you like and continue to make improvements along with the way in how you use it in your system.
"When recipients are watched for standing heat following synchronization, most producers record 80%-85% of the number started," he said. "After culling for CLs (corpus luteum), we typically use only 75% of the total number of recipients [that] began the protocol."
For timed ET, Robertson said he considers 100% to have been in heat at the time of gonadotropin-releasing horomone (GnRH) administration on Day 9. Even after culling for CLs, he said he usually implants 90+% of recipients that began the protocol.
"Pregnancy rates are slightly higher for observed estrus over timed estrus, but more total pregnancies result from the timed heat protocol," he explained. "Timed ET protocols have proven most valuable on farms with less manpower for heat detection and/or lesser trained personnel."
Robertson recommended two "tweaks" for the protocol. In situations where manpower is available and semen cost is negligible, he suggests AIing twice — when GnRH is given and a second time 10-12 hours later. Details on the exact timing in the protocol is included in the proceedings. He said the "tweak" has provided great benefits to some herds.
The second "tweak" involves five-day protocols. CIDRs are left in for five days with PGF given at CIDR removal and again 8-12 hours later. Producers must then watch for observed heats. Robertson did not have data for five-day timed heats for ET.
When it comes to resynchronization for AI and ET, Robertson stressed the open cow is the most costly cow on the operation in either situation. Again, the protocols are outlined in the proceedings. Both involve CIDR use and heat observations on specific days.
"For maximum efficiency of the recipient herd and maximum number of pregnancies in a window of time, recipient re-synchronization is a valuable tool," he said. "On most farms, we try and re-synch all recipients and collect all donors on a 28-day continuous schedule. Recipient resynchronization requires heat detection on those previously receiving embryos. A timely used CIDR prevents lost time in getting a second embryo into a recipient that did not conceive."
The donor schedule with resynchronization is also found in the accompanying paper.
Finally, Robertson encouraged producers to pay strict attention to recipient care in the areas of nutrition, past calving status, housing and environment and health and biosecurity.
"Nutritionally, recipients need to be in good general body condition. If recipients are growing heifers or lactating cows, they should be gaining weight and on a high plane of nutrition," he said. "Likewise, good health is required to conceive. Physical condition should be evaluated."
Most cows will not be suitable recipients at 50 days postpartum. But, he said, farms where strict sanitation is practiced at calving and a well-balanced ration is fed, cows may be more fertile at 50 days than in less well-managed herds at 120 days. Cows on the former have much faster uterine involution, much quicker return to estrus and more ovarian structural development. A comfortable environment is equally crucial for both recipients and donors.
Robertson stressed that all recipients should be tested negative for Neospora canis, and the whole herd should be tested negative for persistent infection with bovine viral diarhea (BVD-PI) and Johne’s disease. The herd should be vaccinated for Lepto hardjo-bovis and other common diseases, but not within 30 days of implantation.
"Have recipients in good condition, externally and internally, and comfortable," he said. "All the technical knowledge available won't offset a poor recipient management program."
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