Recipient Selection
Although not as critical as the donor selection in terms of your operation, it does not lag far behind the donor in terms of the success of your ET program. It does not make sense to choose potential recipients from the bottom of the cow/calf sector. Why place the most valuable progeny you may produce to the least proven or productive cows? That point being made, the ideal recipient does not differ from the ideal donor. I would prefer a 3-8 year old recipient that has calved annually and that has calved 60-90 days prior to implant.
What about heifers? In the earlier years of embryo transfer, I would have said this was ideal from the embryologist standpoint to maximize pregnancy rates but maybe less ideal in terms of a heifer’s ability to achieve acceptable weaning weights on the calves for the producer. Over time, I think this situation has evolved for various reasons to the point now that I would place heifers near the bottom of the selection chain. It seems these heifers are less predictable in their pregnancy rates and seem to incur more failures than mature cows. Some of the fertility issues possibly being involved in those situations could include cyclicity of those animals, growth implants, nutrition (over conditioned and under conditioned) as well as factors we have yet to identify. If, however, that is the animals you have to work with, they certainly can be useful with the understanding of the stated risk.
First calf heifers are also commonly used as recipients. Typically, these are the most difficult animals from a producer standpoint to get pregnant in natural service herds. It stands to reason that they would be the most difficult to get pregnant in embryo transfer. I do believe that is strictly a nutritional issue and very successful pregnancy rates can be achieved in the level of nutrition is increased in this set of cows.
Lastly in the recipient pool are the open cows of unknown origin with the most common source being a sale barn. These are obviously last on my list. My comment to most producers is typically “why do you think they are in a sale barn?” One exception to that comment occurs with a group of mismanaged first calf heifers that never had a reasonable opportunity to become pregnant on the farm. Under proper management and time, they have worked very well.
The statistics say that most collections will produce some non-fertile and degenerate embryos. If your donor has an unusually large percentage of these nonviable embryos, we make sure we address the issues that can cause this effect. The first variable to evaluate is semen quality. Obviously, high quality semen is essential to the success of ET. However, I do believe semen always gets the blame! Be sure your semen is evaluated preferably prior to using in a flush. Just like donor variability in fertility, there is much variation in the ability of bulls to produce viable embryos. If you have any doubts, especially on semen collected from young, highly conditioned show bulls, have your semen evaluated. Also be sure your semen handling techniques are sound. Consistently check your thermometer to assure accuracy. Many other factors affect embryo quality. Stress (hot weather, injury, temperament). Always try to minimize stress in your donors and recips. Finally, there is certainly an inherent genetic predisposition in some donors that make them poor candidates for ET programs. All cows do not produce viable embryos.
The key to the usefulness of this program is accurate heat detection in the recipients. This will not work if you are not able to accurately identify return heats on your recips. I schedule flush days every 35-40 days. This allows you time to check for heats in your recips that are used. Most of those heats will be 12-16 days after transfers (19-23 days from heat). The 35 day interval will allow you time to resynchronize those open recips for the next flush in addition to the recips that are not used or are new to the program. This protocol will greatly reduce the time your recips will stay open and give them more opportunities to get pregnant in an acceptable window of time. The greatest expense in any ET program is the recips. It is very important to maximize pregnancy rates in your pool of recip cows. This program allows you to produce a higher percentage of ET pregnancies in your herd. If heat detection in the recips that have embryos transferred into them is not an option, we can pregnancy check those cows and resynch the open cows on the next cycle. That will still allow you to reuse those recips in a shorter window of time but is obviously not as good as the first plan. What is the best way to synchronize your recips, you might ask. We currently use two primary protocols. When we utilize heat detection programs, we recommend the Select Synch + CIDR (GnRH + CIDR followed in 7 days by CIDR removal + Prostaglandin injection). Recips are then heat detected and time of standing heats are recorded. Only the recips with recorded heats are then checked on transfer day. We commonly use Fixed Time ET (FTET) Programs now eliminating the need for heat detection. The protocol we use is Co-Synch + CIDR. The protocol is the same as for heat detection except the recips are also given a dose of GnRH (Cystorelin, Factrel, Fertagyl) 48 hours after CIDR removal and Prostaglandin injection. All recips are then brought through the chute on transfer day. Typically, we will use approximately 80% of the recips synchronized.
Now that you have followed your schedules and programmed your donors and recipients, it is important that you are prepared for flush day. Manage your cows in the same manner after your heats and breeding as you did prior to procedures. Keep your cattle on their gaining plane of nutrition and continue to utilize all management practices to minimize stress. On actual day of collection, please have your donors up prior to arrival in a comfortable pen. It is very important that you have all of the donor names and registration numbers as well as the sire names and registration numbers. As an AETA certified business, it is our responsibility to be sure that information is provided on all our paperwork but most importantly it must be used when processing frozen embryos. Depending on how many donors are being flushed, the recipient cows may need to be penned also. At least you should have them in a smaller area close to the chute. If you are using “heats” on your recips, have that information also written in a concise legible format. After the donors are flushed, they will be given a shot of prostaglandin to minimize the risk of a retained embryo(s) and a resulting pregnancy in your donors. Depending on your future plans for this donor, it is advisable to give a second injection of prostaglandin 3-5 days later. After transfers are made into the recipients, they should be handled very quietly. If moving them to a new farm or location, it is recommended to move them either transfer day or possibly the next two days. Do not handle them from five days after transfer through twenty-five days to provide them with their best chance to recognize pregnancy.
