Embryo Transfer

How soon can you flush a cow after calving?

Donor cows of beef breeds must be at least 60 days postpartum before the programme starts or 70-100 days into lactation for dairy cows.

It is important to note that cows with a history of calving problems or abortions need to be checked and ultrasound tested to dismiss the possibility of uterine infections and to determine the best time for flushing.

Can you flush heifers?

Yes, however, several considerations must be made before flushing heifers:

  1. In general heifers are more unpredictable and produce fewer embryos than mature cows.  Depending on the breed, you may get 3-4 embryos from a heifer compared to 6-7 embryos from a mature cow. This may be partially due to the smaller dosages of super stimulatory drugs used when setting up heifers.
  2. Heifers cannot be flushed many times. If they are kept open for too long, they usually become overly fat making it more difficult to get them in calf later.
  3. Despite their good showing careers, beef heifers have not proven breeding ability. On the other hand, there is little guesswork involved in dairy breeds given all of the breeding values and production data that producers have available on hand.
  4. Heifers are more sensitive to the super stimulatory drug. Although conservative dosages of FSH are used in heifers, there is always a risk of overstimulation and unsuccessful flushing, on rare occasions, affecting the reproductive functionality in these animals.

How many embryos will a donor produce?

On average donor cows will produce 6-7 viable embryos per flush.

Cows can be classified as good, fair and poor donors.  As many as 1/3 of the cows flushed yield few or no viable embryos at all, another 1/3 are flushes with an average number of embryos and 1/3 of cows will give about 70% of all the embryos produced.

Many factors influence the number of embryos produced by a donor. These include breed differences, age, semen quality, environmental and management factors. However, the most important factor is the individual variation within a breed.

How many times can a donor be flushed?

It varies greatly between cows; some donors can be flushed 8-9 times or more with a steady embryo production while others can only be flushed 3 or 4 times before their embryo production declines.

We recommend flushing a cow 2 to 3 times before deciding if she will be a good or a poor donor cow.

When embryo production declines and becomes uneconomical, farmers must get those cows back in calf. After they calve, it is possible to flush them again and, in most cases, embryo production will be consistent with the previous year’s.

Should I flush on-farm or in-clinic?

To set up donor cows on-farm, you must be able to follow the program precisely, AI properly and to have adequate facilities. The programs are simple to follow and we will send you all the instructions and drugs required.

If you live far away from an ET centre and you want to flush a cow(s) several times, it is more cost-seffective to bring the cow(s) to the centre to be flushed and freeze the embryos.

Some problem cows with recommended modified superovulation protocols may have to be flushed at the centre where we can follow these cows closely.

Certain countries may require cows to be flushed in a quarantine facility.

How soon after flushing can donors be bred?

Donor cows usually show heat from 5 days to approximately 2 weeks after the flush. This is a very fertile heat and cows will be ready to be bred. It is important to keep a close eye on donors. In case you miss this heat, cows can be shot-cycled to be bred and save some time when required. Cows usually have a better chance of conceiving when mated by a bull rather than AI.

Can I use a bull to serve donor cows?

When dealing with row/fresh semen we recommend farmers to get the bull collected. Check the semen and get the donor AI immediately after with 1 to 2 ml of row/fresh extended semen. Letting the bull breed the cow without checking the semen is risky, particularly during certain times of the year or when using very young or old bulls.

Some problem cows only produce embryos when fresh semen is used, in this case, you can bring the bull to the ET centre to collect him and AI the donors. We can also make arrangements with the stud centre to get fresh extended semen from some bulls and AI donors. A key advantage of getting fresh extended semen from the stud centre is that we can still produce embryos that qualify for export purposes; this is different when the bulls get collected on-farm or at the ET centre.

Row/fresh semen work well in donor cows and usually one AI is enough, so the bull does not have to be collected twice. We can keep extended semen in the refrigerator if second breeding is required.

How many times should I breed the donor and how many straws of semen do I need?

Normally cows get inseminated twice, 12 hours apart with one straw of semen each time. It is recommended to have an extra straw of semen in case one explodes. Alternatively, if the cow shows a delayed or extended heat, she can be bred one more time. The second breeding of the program is the most important so it is vital to ensure that you have enough semen at this time.

In certain cows, we may have to modify the breeding protocol by increasing the amount of semen and the number of times they may need to be bred.

When setting donors in-clinic, we require you to provide us with 3 straws of semen.

What to do if the donor cow does not show heat?

You must follow the program and breed on time. Many times donors have a good response and produce embryos without any visible signs of heat.

Some of these donors may have a small or poor response to the drugs, in these cases, you may have to consider changing the breeding if you are dealing with expensive or rare semen.

Can I flush my donors on-farm to produce embryos for export?

Yes, you can, our mobile unit is export certified. On rare occasions, some countries, such as New Zealand, require that cows are in quarantined (or isolated) pens while they are in the process of producing embryos.

Although we always process and wash the embryos to qualify them for export for most countries, we need to know if you intend to export them and to which country, in case there are special requirements or testing of donors needed.


When is a cow ready to be used as a recipient?

The number of days since calving is an important factor which affects the proportion of cycling cows available as recipients. The number of cycling cows usually peaks between days 70 to 80 postpartum. There is an increment of about 7.5% for every 10-day interval since calving from <50 to >70 days. For this reason, it is recommended that recipients are at least 60 days postpartum and the longer you can wait, the better.

The use of cycling animals as recipients for an embryo transfer program should maximize the portion of animals that will receive an embryo and conceive.

Particular attention should be paid to 2-year-old cows when they are nursing calves. In general, young cows tend to have prolonged anestrous due to their additional growth requirements. The percentage of 2-year-old cows cycling at the time of the breeding season is less when compared with older cows in the herd, even though they calved 2 to 3 weeks early.

Should I use cows or heifers as recipients?

There are some advantages to using cows as recipients. Most of the time, we know the reproductive performance and ability to milk to raise an ET calf. When using cows. we prefer cows that have calved between 3 and 6 times. Moreover, cows are better suited when transferring embryos of breeds with relatively large calves or embryos with an estimated high EPDs for birth weight.

Heifers work well as recipients. This is because they can average 5 to 10% better pregnancy rates when compared with cows managed under similar conditions. This is likely because heifers do not have to deal with lactational stress as well as lower incidence of subclinical or clinical uterine infections.

Cows that have been used successfully as recipients tend to repeat this in the following year; we encourage retaining and re-using these kinds of animals.

How many recipients should I set up?

It depends on what you want to do with the embryos from a flush and/or if you have some frozen embryos that you want to use the same day.

It also depends on the synchronisation protocol to be used i.e. CIDR & GnRH based protocols vs. one or two prostaglandin injection protocols.

Usually, approximately 15% of cows do not respond to the CIDR/GnRH based synchronisation protocols. We recommend synchronizing 8 to 10 recipients for each donor cow if you are planning to implant most of the embryos fresh. If you get more embryos than recipients ready, we transfer the lower grade embryos and freeze the better ones for later use.

If you have frozen embryos available, we can bring them and use them in case there are not enough fresh embryos produced by the donor(s). This is a risk, especially when flushing only one or two cows. This ensures that we are not wasting the recipients.

Another option is to flush a cow and freeze all the embryos; you can set up 3 to 5 recipients only to implant marginal embryos (embryos that do not freeze well), then prepare a bigger group of recipients for her second flush once we know her reputation as a donor cow.

Natural heats also work well for implanting embryos. It is also a good idea to check the rest of the herd for heats that may occur a day before, during, and a day after the donor cow will be in heat. These cows can be utilized in case extra recipients need it. It is important to note that asynchrony of 24 hours or more has a negative effect on conception.

Do I need to check for heats?

Heat detection and recording are important for the success of the ET program. Some synchronization protocols require that special attention is paid to heat detecting, especially when using only prostaglandins to bring cows into heat.

To synchronize recipients we use a CIDR based protocol, some of what is used in a fixed time AI programme. Although these protocols are more flexible regarding heat detecting, we still recommend and check what kind of activity is happening in the recipient pens when they are supposed to be in heat.

Recipients should be clearly identifiable with a large ear tag, especially to record the ones that did not show any signs of heat. These cows need to be ultrasound tested before we decide on whether they will be ready to receive an embryo or not.

When can I “preg” check my recipients?

If you are in a hurry to re-use or re-synchronize recipients they can be ultrasound tested at 21 to 23 days after being implanted. However, if you are not in a rush, we recommend doing it at day 60 of pregnancy or later.

Do not sell or slaughter recipients that have received embryos until they have been confirmed as non-pregnant.

What kinds of facilities are required for transferring embryos?

The facilities required do not have to be fancy but should be functional, allowing the cattle to be handled efficiently with a low level of stress. Moreover, they must be able to provide adequate restraint for recipients. Most cattle squeezes work well for this purpose and we should be able to place a pole behind the animal and adjust it according to their size, since, in many cases, cattle stand better without catching their heads.

A palpation cage or a door installed on one side of the chute is important to avoid climbing the fence every time. Good facilities make everyone’s job easier and increase the chances of success.

Should I transfer fresh or frozen embryos?

The freezing and thawing process is very intricate for embryos and usually results in an approximate 5 to 10% reduction in pregnancy rates. Therefore, we always try to implant as many fresh embryos as possible.

Can I AI implant recipients if they show heat again on their next cycle(s)?

On many occasion, implanted recipients show heat again afterwards, despite being pregnant. Some of these cows may show heat at different stages of pregnancy, especially when other cows bulling around. For this reason, you should not A.I. recipients the first time they show heat, wait until they have been confirmed open. The use of natural breeding will be a safer option in these cases.

The same principle applies when trying to ship or sell recipients. Get them “preg” checked.

Can I process and vaccinate recipients while they are getting set up to implant embryos?

NO, plan ahead for your vaccination program. You should NEVER vaccinate recipients within 30 days of the date they will receive an embryo. Caution should be taken when vaccinating calves nursing recipients and/or recipients before and after an embryo has been implanted, particularly with modified live vaccines for VBD and IBR.

Avoid pour-on medications 2 to 3 weeks before the implanting date. Get the animals tagged before the implant day, this speeds up the work and recipients are under lower stress.