Although most of the applicable embryo transfer (ET) technology was developed in the 1970s and 1980s, embryo transfer in cattle has recently gained considerable popularity within the purebred cattle industry. It is one of the most economical and fastest ways of preserving and multiplying cow’s genetics, more cows get flushed every year and enrolled in the genetic improvement programs of beef and dairy producers.
With the embryo transfer technology, it is possible to exploit the vast reproductive potential of a genetically important cow. While a cow can produce an average of 8 to 10 calves in her entire lifetime under normal management programs, ET technologies can greatly increase the amount of offspring from these cows, usually referred to as “donors”. In some instances ET is used to achieve more pregnancies from very expensive or rare semen.
When a donor cow enters an ET program, her embryos can be transferred fresh into recipient females or can be frozen and stored for later use. The process of collecting and transferring embryos requires that the estrous cycle of donors and recipients be synchronized. This is achieved by the administration of reproductive hormones that are given in a timely manner. The purpose of the hormonal treatments in a donor cow is to super-stimulate the ovaries to produce and release more ova (eggs) at the time of breeding, these fertilized eggs will develop into embryos that will be collected at 6.5 to 7 days of age. The treatments for recipients cows are intended to synchronize their heats. These cows can receive an embryo 6 to 8 days after having a heat. Natural heats in recipients can be used to implant embryos as well.
Selection of donors is very important. Donors are usually selected on the basis of superior genetic merit compared with the rest of the herd. Whether the criterion is performance records, show ring appeal, or both, consideration must be given to the potential dollar value of her calves.
The potential donor cow should be reproductively sound to produce maximum results, some of the important criteria to look for in prospective donors are:
Normal postpartum history
Regular heat cycles (length of 18 to 24 days)
Body condition of 2.5 to 3.5-4 (skinny or fat animals tend to do poorly in most cases)
Heifers are more unpredictable than cows and usually produce fewer embryos. Heifers should be 350 kg or more, be cycling and have a well developed reproductive tract.
Young cows are usually preferred (3 to 8 years old). Embryo production in old cows varies greatly depending on their genetics, but in general the older the cow gets, the lower the chances of being a successful donor.
Cows need to be under a good nutritional plan including mineral supplementation.
Maintaining or increasing an acceptable body condition. Cows losing condition or over-conditioned have a lower reproductive activity.
Reproductive tract examination:
It is always recommended that cows are palpated and tested by ultrasound before entering into the ET program. When preparing donor cows to be done on-farm, your local veterinarian can examine your cows to determine the status of their reproductive tract.
Normal uterus involution after calving.
Discard the presence of pathological conditions including uterine infections, if there is a problem, it needs to be treated accordingly before a cow is place into an ET program.
Ensure that the cows are open.
Determine the presences and quality of normal ovarian structures. Cycling vs. non-cycling.
Presence of abnormalities such as cystic ovaries, adhesions of scar tissue, etc.
Vaccinations should be up to date. Pay special attention when using modified live vaccines for BVD and IBR. If vaccinating, cows need to be done 40 days or more before starting the super-ovulation protocol.
Do not dip the cows with pour on medications for at least 10 days before starting the super-ovulation protocol.
Handle donors calmly and keep them under as low stress environment as possible.
CIDR application and injections can be administered by the producer right on-farm as it is easy enough.
Apply CIDRs. It is recommended to rinse and disinfect your CIDR applicator between cows.
Ensure that all injections are administered intramuscularly (the neck region is preferred especially in over-conditioned cows).
When giving injections, always check donors to ensure the CIDR is still in place.
See image below for typical super-ovulation protocol for donor cows.
Two inseminations are required and are performed 12 hours apart; the timing of the 1st breeding will depend on the super-ovulation protocol to be used.
Use high quality semen, in general it is recommended to have three dosages of semen on hand in case one may explode or the cow shows an extended heat that will require a 3rd breeding. On some occasions and under specific circumstances a few more straws of semen will be recommended.
If there is any doubt regarding the quality of the semen to be used, please let us know. We can evaluate frozen semen prior to use, increasing the chances for success by discarding potentially infertile or sub-fertile semen.
Save all semen straws for us and attach them to the super-ovulation record.
It is recommended to have an indoor place to flush a cow since at certain times of the year the environmental conditions can be unpredictable. Donor cows cannot be flushed outdoors when is raining, too cold, or extremely windy.
Have the super-ovulation record filled out and returned to us.
Please check and let us know if the cow needs to be DNA tested.
NOTE: Keep us informed with the development of the program. In case of any problems or if you have any questions, please let us know so we can help with the situation before is too late. Make sure the instructions are understood and followed precisely, since these programs are very sensitive.
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.
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.
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.
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.
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.
Animals with temperament problems should be removed from the program.
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.
Cows need to be at least 60 days post-calving, when possible, it is recommended to wait a little longer (75-80 days).
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.
Administer Vitamin A, D and E and mineral supplementation at least 4-6 weeks prior to implanting.
Recipient identification is essential, tags must be easy to read and whenever possible put tags in both ears.
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.
Do pregnancy diagnosis on every recipient before getting them in an ET program.
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.
Move recipients slowly and keep them calm at all times while they are getting used to the handling system.
3. Preparing Recipients:
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.
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).
How to apply CIDRs. It is recommended to rinse and disinfect your CIDR applicator between cows.
See image below for typical synchronization protocol for recipients.
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.
4. Implanting Day:
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.
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.
All recipients get an epidural just before getting implanted and they must be herded slowly right after.
Depending on the program used, it may be required to have the heats and breeding records on hand the day of implanting the embryos.
Never hesitate to contact us with any problems or questions about the program. Communication is vital.