This mainly depends on the cow’s own potential to ovulate multiple oocytes and is difficult to answer. Factors that influence this potential is breed, age, body condition, calving’s and lactation, where embryo quality is affected by the quality of semen used, environmental factors, like climate and rainfall, feeding factors, stress on the animal, farm management, disease and also the reproduction organs of the donor.

The average embryo production is 5 embryos per flushing for a cow and 3 for a heifer.

We normally suggest no more than 3 flushing’s per donor and then to make them pregnant with natural breeding or artificial insemination (AI). The embryo production may influence this dependent on the total embryos needed.

Another reason to stop producing embryos, is when the donors’ total embryos produced per flushing’s starts lowering in quality and quantity.

Firstly, if the donors’ embryo quality and quantity start decreasing, the process becomes less cost effective.

Secondly, because of the lower quality the conception rate of embryo transfer is also lower and further decreases cost efficiency.

Lastly, because of multiple cycles of hormone stimulations (with each flushing) the chances of the donor to become pregnant again, is lowered. The more flushing’s, the more difficult the becomes. Although it will depend on the donor self.

Pregnancy “resets” a donors’ reproduction and therefore can be flushed again after calving. After calving the ovaries have once again gone back to normal and can repeat the same cycle.

Since all cows are different you can keep flushing a cow for many years if you see her quality and quantity does not change or weaken, and a cow only struggles to fall pregnant when she has picked up too much weight so having her be more active will ensure her to fall pregnant.

We suggest a Vitamin ADE and Mineral (Se + Cu) injection on the intended donor, as soon as 40 days after calving. With the start of the hormone program at 60 days and embryo flushing at 75 days after calving.

When the donors are more than 3 months after calving, the lactation stress can affect embryo production and quality, but after 6-7 months the production potential increases again.

Heifers, as well as any donor, should be inspected by a veterinarian before selection for embryo flushing. To ensure that the reproductive organs are developed, in good order and active before starting a program.

We also prefer that the heifer has reached 2/3rds of her expected mature weight. Starting embryo production on a heifer at a too young age can affect her potential indefinitely.

Heifers have the advantage that they do not have lactation stress, but keep in mind that heifers naturally produce fewer embryos than mature cows. They have not proven their breeding ability.

Heifers are more difficult to get pregnant after multiple flushing’s (over flushing’s). It is suggested to only flush a heifer twice before making her pregnant.

Spring and autumn are generally good seasons for embryo production, due to the moderate weather, but it is important to pick a time where the temperature is more constant. Big fluctuation in day/night ambient temperatures, will influence embryo quality.

The best time for on-farm embryo flushing will be determined by the location of your farm, the breed you wish to flush, feeding availability, expected calving date and recipient availability.

Times to avoid embryo flushing is between 20 June and 31 July. The shorter days and low nights temperatures influence the reproductive activity of cattle. On the other hand, the high day temperatures from December to January can have the same negative affect.

After weaning (or without a calf) a donors’ potential for embryo production is highest, but flushing a dry cow gives low reproduction records (for instance inter calving period).

We accommodate cows with calves at our embryo centre, if you wish to produce embryos from cows in lactation.

Donors can be flushed as soon as 70 days after calving.

Lactation stress influences embryo production most between 100 to 200 days after calving.

Firstly, we grade embryos according to the development phase. Morula (M), Early Blastocyst (EB), Blastocyst (B), Expanded Blastocyst (XB) and Hatched (H) are the common developmental phase with embryo transfer.

Thereafter we grade according to quality. Grade 1, 2, 3, degenerate or oocyte.

• Grade 1 Embryos: where more than 85% of the total cellular material of the embryo is alive and normal
• Grade 2 Embryos: between 50% and 85% of the total cellular material is alive and normal
• Grade 3 Embryos: where less than 50% of the total cellular material is alive and normal
• Degenerates are unviable embryos (dead) and Oocytes are unfertilized gametes.

Grade 1 embryos are most likely to survive, with conception rates up to 60% with embryo transfer. Whereas grade 2 and 3 embryos have a conception rate as low as 30%.

Grade 1 embryos are also preferred with cryopreservation (freezing). The conception of frozen-thawed embryos decrease with 10% of their fresh ability.

Example of embryo grading: We will write M1 on the embryo flush sheet, which means Morula + Grade 1.

Artificial Insemination (AI) in a flush program is repeated 3 times over 24hours. We need at least 1 straw per AI but can use two depending on quality.

If the semen is readily available, we will use 2 straws at the time of standing the heat and 1 straw for each of the other AI’s.

Thus, 3 to 6 straws are required for an embryo flush program.

Factors influencing embryo production due to the donor herself:

• Some donors do not respond well to superovulation drugs, which can result in poor quality or degenerate embryos
• Body Condition: If the donor is to thin or to fat.
• Lactation stress: time of lactation
• Breed: Adaptability, temperament, etc.
• Fertility: inter calving, heat cycles, reproductive activity and structures
• Age:
  • Heifers are normally highly fertile if bred at the correct age and weight.
  • First calf cows are normally more difficult to get pregnant for a second time and have lower production rates
  • Cows that calved more than two times normally has the best ability to get pregnant and the same with embryo production

Semen quality: semen should be collected by an Artificial Insemination Centre, evaluated by a trained specialist and stored under proper condition. The livelihood, movement, longevity, abnormalities and total sperms will determine the quality of semen.

With embryo flushing, the need for proper quality semen is not just important because of the costs that go into the program, but also because of the superovulation hormones used for the donors. With this program, the spermicides need to be able to swim further up the uterus, and the survive much longer as the cow may ovulate over a longer period.

We calculate hormones for a donor specifically and therefor mistakes like wrongful dosage or missing steps in the program can have detrimental effects on the success of the program. Management!

It is important to manage the diet of donors and recipient to ensure optimal health and body condition throughout the program and continue with recipients or for repeat flush donors. Changes in feed type or ration cause the animals to stress and reproduction is highly influenced by stress. Management!

If the person performing Artificial Insemination of the donors struggles to get through the cervix or damages the wall of the uterus wall in any manner, it will result in fertilization problems.

Calculation of hormones with the first flushing can cause problems since we do not know how a new donor will react to follicle-stimulating hormone. Resulting in a possible too high or too low dosage and either low or no production of embryos. It is important to take phase of lactation, body weight, condition, breed and season into account.

Sudden temperature changes affect embryo production highly. With sudden low temperature, like cold fronts, the body takes nutrients away from reproduction to maintain body heat for survival. With very high temperatures, like heat waves, the body uses more energy to cool itself down, the energy that comes from nutrients needed for reproduction…

With the rain, it is important to provide shelter, as wet bodies also get cold. Thunder can also cause stress which has a negative effect on reproduction.

We cannot change the environment, but we need to manage it to the best of our ability to ensure that the influence is as little as possible. If the environment changes suddenly, it is important to ensure that adequate feed is available to help prevent the reduction in nutrient available for reproduction.

We regularly do farm flushing, but it depends on the following:

• What is the level of management on the farm? If the program can’t be followed precisely or there are no facilities to do a flush or transfer, then we will recommend the cattle comes to our station.
• How many times would you like to flush the cow? If you live in a remote area and you want to flush every 2 months, it will be more cost-effective to send the cattle to the station where we can freeze the embryo’s and travel only for embryo transfer.
• Would you like to export the embryos? If yes, then the cattle must be flushed at a quarantine facility.
• How many cows would you want to flush? It becomes expensive when flushing only a few donors, so we will advise you to send them to the station. Another option is to get a nearby farmer to share travel costs with you and we flush both on the same day.