RECIPIENT SELECTION, EVALUATION & TRANSFER PREPARATION
A practical guide, by dr. Robert Treadwell, Embryo Plus
Selection of animals to be recipients to Boran embryo’s
There are 3 basic criteria to select recipients:
1) They must be able to cycle normally and become pregnant
2) They must be able to maintain the pregnancy and have a normal partus
3) They must be able to raise the calf well
Keeping this in mind all the time, one then has to decide
between the following options:
Heifers vs cows
Heifers have the advantage that they do not have any lactational stress, therefore they usually cycle better than cows. They usually have a very low incidence of clinical or subclinical genital tract infections, compared to multiparous cows. Because of the lower metabolic maintenance requirements, they are relatively cheaper to feed that adult cows.
When using cows, there are definitely also some advantages, especially if the policy in that specific herd has been to cull strictly on reproductive performance and the ability to properly raise the calf. If, in such a herd, you are presented with a cow that has had between 3 and 6 calves, you know you’re dealing with functionally fertile animals. They will also be better suited when transferring embryo’s of donors cows or bulls with relatively large calves at birth, although small calves at birth is a characteristic trait of the Boran and birthweight is usually not a consideration in Boran embryo programs.
Mature cows usually have more milk than heifers to raise the calf and any temperamental problems would have been noted previously in her life. This is quite important, as a lot of the temperamental problems seen in calves may be related to behaviour adapted from the dams, and in embryo calves this is no different.
Animals used successfully before as recipients tend to repeat this in a next breeding cycle, making them very valuable. The owners should try and retain their successful recipients.
In the case of beef breed recipients , we usually start synchronizing them to transfer at 3 months post partum. There will always be exceptions where animals reconceive earlier, but at a drug fee of about R100 per individual synchronization program and the value of the embryo, it is usually cheaper to wait. If you wait too long, the nutritional needs of the suckling calves becomes too much and the cows go onto a negative plane of condition.
I prefer using them between 3 to 4.5 months after calving, alternatively letting them wean first before using them. With adequate nutritional assistance, calves can be weaned at 5 months without problems in order to get their mothers ready for embryo transfers.
In the case of heifers we use the same guidelines as for normal breeding, that is about 65% of mature weight at the time of transfer. Breed differences and nutritional management on the farm determines the age at which heifers will be ready for transfer.
In my opinion the worst recipients will be first calvers with calves at foot. These animals are still growing out, have added lactational stress and are the most difficult group to get pregnant even by normal means. I would not recommend using first calvers, except if you’re prepared to wait until the calves are weaned.
Different breeds of recipients
There are many different factors to consider when choosing a breed of recipient.
Fertility, temperament, adaptability, calving ease and adequate milk must all be considered.
The most Continental or European breeds have good fertility. Dual purpose type animals usually raise beautiful calves because of the extra milk. Most dairy breeds have very good temperament. All of this means nothing if they die of tick borne diseases or suffer because of extremes in temperatures or parasite burdens.
In most cases you do not really have a choice, because either the recipients will be genetically inferior animals of the same breed as the embryo or be from the commercial part of the farming enterprise.
When you are asked to make a recommendation, one must use recipients that are suited for that specific farm’s management and for that specific area. Use hardy animals for extensive, semi desert type conditions and give the heifers enough time to mature properly before using them as recipients.
It is better to have at least 50% Bos Taurus in the recipient instead of using pure Brahman. Recipients with 50% Boran blood work really well when transferring Boran embryos.
More early maturing, European type animals can be used in mild climates with adequate nutrition or artificial pastures.
Some breeders use dairy heifer to transfer embryos into. Once they have calved down, they let one cow rear 2 or 3 calves on her own and sell the other recipients as fresh in milk dairy cows, with obvious economical advantages.
Although Jersey heifers are probably some of the most fertile recipients around, we have experienced resorptions, abortions, failure to go into partus and the birth of stillborn calves quite regularly when using them as recipients for specifically Boran embryos in the past and I would not recommend using them. The specific scientific reason for this is not completely clear yet.
Own animals vs. buying in
Using animals that were raised by the breeder himself is a far better option than buying in animals to be used for recipients, because you know the real age, nutritional state, vaccination status, calving history, etc.
If you have to buy in animals, try buying from respected breeders that you trust and try and buy from total dispersal sales. If you buy a group of open heifers from an unknown source, they may very well be his most infertile animals that did not conceive after running with the bull for various reasons. Heifers that were neglected while growing up as far as nutrition goes are very often stunted for life and will always be of lower fertility.
Buying open cows without young calves at foot is buying someone else’s problems. If you plan to buy in cows, it is then better to plan well in advance, buy pregnant cows or with small calves at foot and wait for a few months longer while they calve down and adapt to your circumstances.
2) Preparation of recipients
“How many recipients will we need?” is a frequently asked question and a very difficult one to answer. The number of recipients that are suitable to use out of the initial group that was prepared depends a lot on the quality of the recipients, their nutrition and management, climatic conditions during the program etc. A rough estimate is to prepare twice as many recipients as the number of embryos you have or expect to get. It is always a good idea to have extra frozen embryos available, should you end up with more recips that have reacted correctly for transfer. Given the current value and the demand for Boran genetics, it makes economical sense to prepare more recipients that will enable the vet to only use the very best ones and give you a better conception, rather than trying to save money on the synchronization and ending up using border line recipients.
We prefer to give recipients two opportunities to get pregnant from embryo transfers, and if she is then unsuccessful, to rather have her removed from the program. In certain scenarios we will give a recipient a third chance, but the percentage of them that is ready for a transfer and fall pregnant on the 3rd round of transfer is lower.
Animals brought from another area or from a different nutritional system require at least 3 months adaptation period on the farm where the transfers will be done.
When receiving a new group of animals onto the farm or getting a group of animals ready for transfer, liase with the local vet and get the following in place:
- Test for TB and Brucellosis at least.
- Do pregnancy diagnosis on every animal, even if she has “never been close to a bull”. At the same time examine the recipient for breeding soundness and ovarian activity. Cows with calves at foot can be routinely douched at one month post partum to make sure she does not carry any subclinical uterine infection into the embryo program.
- Vaccinate against relevant diseases, especially diseases directly affecting fertility like BVD. If they are going to be moved to a Heartwater, Redwater or Gallsickness area later after receiving embryos, make sure that the immunization occurs before the transfer synchronization starts.
Proper identification of the recipients is essential. Eartags must be clearly visible from a distance. Put eartags into both ears, as they get lost regularly. Make sure there is no duplication of recipients with the same number. A permanent hot iron brand would be ideal, tattooing and the small metal type eartags is also a good option. Do this well in advance as not to stress the recipients too close to the time of the transfers.
Nutrition is obviously extremely important and warrants a separate discussion on its own. A new breeder should get a nutritionist to assist him. It is better to start with animals slightly down in condition and get their condition to improve during the program, than to start with fat animals that only maintain their condition or even lose condition. A condition score 2 to 2.5 animal at the start of the program that gains condition to a 3 to 3.5 at the time of transfer is ideal.
Correct any micromineral imbalances or deficiencies prior to the program. We give Vitamin ADE and Multimin as part of our synchronization as well, but at least 3 weeks prior to transfer.
Guard against high levels of NPN in the diet. Sudden changes in diet close to time of transfer is not advisable and after the transfers the recipients should stay in exactly the same grazing conditions (same camp if possible) and on the same nutritional program at least until 2 months after transfers when the pregnancy diagnosis can be performed.
Cows with small calves at foot can be nightweaned if possible and the calves receive additional concentrates during the night.
Take care not to get the recipients in an over fat condition at the time of calving, with the resultant dystocias, etc.
Animals with temperament problems should be removed from the transfer program. If you’re dealing with recipients managed under very extensive conditions, organize for them to be taken through the handling facilities where the transfers will take place at least once a day for a month before the actual transfer takes place to get them accustomed to the setup and bring their stress levels down. Work quietly and calm, no dogs/electrical prodders/whips, etc.
It is the transfer vet’s responsibility to inform the breeder about the minimum requirements for handling facilities, as this has a direct effect on the temperament and stress levels of the recipients.
It obviously also affects the quality of your work and the conceptions you achieve if the vet has to climb over 2 meter high fences 200 times a day, work in 40 degrees C in the sun with inadequately restrained recipients. Shade for the thawing process and a gate through which the vet can get in behind the restrained recipient is necessary.
There are many different ways of synchronizing the recipients, each with certain advantages to it. We use mainly progesterone implants (Crestars, Cidrs or Cue-Mate), combined with prostaglandin and PMSG. Where at all possible, natural heats are the best, but not very practical. Regimes with only prostaglandin injections also work well, provided you’re dealing with animals that are cycling normally already and you have time to transfer on consecutive days, as your synchronization is never as close as with using the progesterone devices. The different programs for different sets of conditions is also a discussion on its own.
Heat spotting is an extremely important part of the program. This allows the transfer vet to better interprete his palpation of the ovaries and to match the age of the embryo to the onset of oestrus, which ensures better conceptions. If you’re dealing with big group of recipients, divide them up into more manageable groups of not more that 40 animals. It helps to remove the animals that have been seen on proper standing heat to a separate camp as to get subordinate animals to show heat as well. Get a dedicated person to do heat spotting for the 3 days, also at night time if possible. The importance of easily readable eartags is obvious. Use aids like teaser bulls, heat detection devices as far as possible, but they must never replace proper observation time spent with the animals. Good recordkeeping of the time of onset of standing estrus is important.
3) Evaluation and transfer
Planning is essential as to waste the least amount of time from the collection of the embryos to either freezing them or transferring them. If you suspect that you may not have enough recipients available for the number of embryos you expect, examine the recipients before starting to flush. In that case you can then finish your flushing, freeze the better quality embryos immediately and start transferring while the freezing process is under way.
We give the recipients a sedative at least 10 minutes before transferring, using between 10 and 25 mg of Acepromazine maleate, depending on the size of the recipient, the breed and the “temperament requirements”. If you give too much, they tend to go down in the neck clamp. It also affects their temperature regulation, so make sure that they have access to shade and water after injecting them. The use of the sedative allows you to work with less risk of sudden movement from the recipient that may cause damage to the uterus while transferring, or damage to the vet doing the transfer. An added benefit of the ACP is the mucous secretion it causes from the vulva. This acts as a sort of lubrication for the transfer pistolet and when dealing with a subclinical case of endometritis , you may very often see specs of pus in that mucous secretion when you insert your hand into the rectum, acting as a timely warning not to use that cow for a recipient.
When examining the ovaries, we try not to touch the uterus, because the resultant prostaglandin release may cause luteal tissue regression. This is why it is necessary to have the genital tract examined before the program for infection and possible pregnancies. We always examine both ovaries and grade the corpus luteum according to the side, size and age. It’s important to know the time of onset of estrus, as the CL may differ in size between a 6 day and a 8 day old CL.
(Note- when you are AI’ing donors during an embryo flushing program, NEVER TOUCH THE OVARIES. You interfere with the normal ovulation and fertilization and may cause the oocytes (eggs) to be lost into the body of the animal).
Keep records of the vet’s findings, but also mark the recipient with a livestock marking crayon. It helps to sort out the recipients after the transfers and may be an aid if anything goes wrong and the recipients get mixed.
The embryo vet gives an epidural to the recipient as to not have her straining and moving around too much. Good facilities obviously important as well in this regard.
The effects of the epidural takes about 4 hours to subside, so do not let the recipients walk long distances after the transfers or over difficult terrain. They must be herded slowly.
Keep a record of the recipient detail (breed, colour, day on heat, grade, side of the CL ) and the info on the embryo (grade, sire, dam, fresh or frozen).
I prefer not to tamper with the recipients at all before the pregnancy diagnosis is done. Wait 8 weeks before examining them, because some embryos develop slower than normal pregnancies and may be missed, even by an experienced vet, if the examination is done too early. Ultrasound is another option, but with the relatively high number of “normal” resorptions between 28 days of pregnancy and 56 days, its use is debatable, unless the unsuccessful recipients need to be used again right away.
Sometimes the breeder insists on breeding the recipients that return to heat.
It very often happens that recipients that have received an embryo show heat again afterwards, even though she is pregnant. Do not AI the recipients on the first time she shows heat signs after the transfer. When she shows heat a second time, she can be inseminated but take care to only manipulate the AI pistolet to the internal opening of the cervix and deposit the semen there without advancing into the body of the uterus at all, for the small chance that she may still be pregnant. To use a bull would be the safest.
Any change after transfer is bad. Keep the recipients in the same camps, same nutritional conditions and same management as far as possible after the transfers until the pregnancy diagnosis has been performed. Try not to disturb them at all, and do not “spoil” them because of her precious possible pregnancy.
Communication with your embryo veterinarian is obviously vital. Never hesitate to call with any possible problems or when there is uncertainty over anything about the program. It is also a good idea to have your breeding records available on the day of transfers, should there be questions on a specific recipient.