How soon can you flush a cow after calving?

  • Donor cows of beef breeds must be at least 60 days post-partum before the program starts or 70-100 days into lactation for dairy cows.

  • 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, but a few things need to be considered before flushing heifers:

  • 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 can also be due, in part, to the smaller dosages of super stimulatory drugs used when setting up heifers.

  • 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.

  • Despite their good showing careers, beef heifers have not proven breeding ability. On the other hand, for dairy breeds there is not much guess work to do with all the breeding values and production data that producers have available on hand.

  • Heifers are more sensitive to the super stimulatory drugs; although, conservative dosages of FSH are used in heifers, there is always a risk of over stimulation 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 are cows that will give about 70% of all the embryos produced.

  • There are many factors influencing the number of embryos produce by a donor, including breed differences, age, semen quality, environmental and management factors, etc. However, most important is the individual variation within a breed.

How many times can a donor be flushed?

  • It varies greatly between cows, while some donors can be flushed 8-9 times or more with a steady embryo production, others can be flushed only 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, we need to get those cows back in calf. After they calve, we can flush them again, and in most cases they tend to be consistent with their embryo production from the previous year.

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 effective to bring the cow(s) to the centre to be flushed and freeze the embryos.

  • Some problem cows with recommended modified super ovulation protocols may have to be done at the centre where we can follow these cows closely.

  • Very few and specific countries may require cows to be flushed in a quarantine facility.

How soon after flushing can donors be bred?

  • Donor cows usually show heat anywhere from 5 days to around 2 weeks after the flush, this is a very fertile heat and cows will be ready to be bred. 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?

  • What we recommend when dealing with row/fresh semen, is 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 get him collected and AI the donors. We can also make arrangements with the stud centre to get fresh extended semen from some bulls and AI donors. The 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 works great 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 a 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 may explode or 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 you need to ensure 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.

  • It is possible that 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, there are rare occasions in some countries, ie New Zealand, where cows need to be 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 would 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?

  • An important factor affecting the proportion of cycling cows available as recipients is the days since calving. The number of cycling cows usually peaks between days 70 to 80 postpartum. There is an increment of about 7.5% for every 10 days 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 in order to raise an ET calf, when using cows we prefer  cows that have calved between 3 and 6 times.  Cows are better suited when transferring embryos of breeds with relatively large calves or embryos with an estimated high EPD’s for birth weight.

  • Heifers work good as recipients as they can average 5 to 10% better pregnancy rates when compare with cows managed under similar conditions. This is probably due to the fact that heifers do not have to deal with lactational stress, lower incidence of subclinical or clinical uterine infections.

  • Cows that have been used successfully as a 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 of the synchronization protocol to be used i.e. CIDR & GnRH based protocols vs. one or two prostaglandin injection protocols.

  • Normally about 15% of the cows do not respond to the CIDR/GnRH based synchronization protocols. We do recommend synchronizing 8 to 10 recipients for each donor cow when 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 from the donor(s), this is a risk especially when flushing only one or two cows. This way we would not be 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 good to implant 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 are need it. Asynchrony of 24 hours or more has a negative effect on conception.

Do I need to check for heats?

  • Heat detection and recording is important to the success of the ET program. Some synchronization protocols require special attention 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 program, 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 make a decision 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. But if you are not in a rush we do recommend doing it at 60 days of pregnancy or later.

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

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. We always try to implant as many fresh embryos as possible.

What kinds of facilities are required for transferring embryos?

  • Facilities do not have to be fancy but should be functional, allowing the cattle to be handled efficiently with a low level of stress and be able to provide adequate restraint for recipients. Most cattle squeezes work fine 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.

  • palpation cage or a door installed on one side of the chute is important to avoid climbing the fence every time. Good facilities make everybody’s job easier increasing the chances for success.

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

  • It has happened many times when implanted recipients show heat again afterwards, despite them being pregnant. Some of these cows may show heats at different stages of pregnancy especially when there are 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.