The Process

Embryo transfer is a genetics progress tool – a way to achieve genetic goals faster. The process comprises a series of operations, each of which needs to be carried out successfully in order to maximize the results of your program. Failure of just one part of the procedure can lead to failure of the overall program.

These guidelines have been developed based on the experience of our veterinarian team interacting with clients to help avoid oversights and achieve success in applying embryo transfer.

DONOR PREPARATION

For consideration in the ET program, all donors should undergo the following to ensure their suitability:

- Donors should be selected based on superior genetic merit; ideally produced a calf each year; be reproductively healthy
- Donors should be palpated by your veterinary to ensure suitability prior to the first injection of hormones
- Donors should be at least 8 weeks post calving before the programming begins
- Donors as young as 12 months can be used, however, virgin heifers and older cows are less predictable in their response to super-ovulation program

RECEIPIENT PREPARATION

The following guidelines should be used in recipient selection;

- Recipients should be reproductively sound, with no history of infertility or calving problems. Open heifers ready to breed (16+ months and 350+ kg), and younger animals having one or two calves are ideal recipients.
- Cows with more than 5 or 6 calves should be avoided for use as recipients, especially if they have shown any fertility problems such as retained placenta or infected uterus.
- We advise that all recipients be tested for LEUKOSIS and NEOSPORA prior to synchronizing them to receive an embryo. These tests will help you select recipients with the greatest chance of producing a live healthy calf from your ET program.
- All recipients in the program should be palpated by your local veterinarian to ensure their suitability prior to the first injection of hormones

NUTRITION AND EMBRYO TRANSFER

As a rule of thumb, the donor and recipient cattle should be on a rising plane of nutrition to achieve maximum embryo fertility and pregnancy rates.

Animals that are being flushed repeatedly should be put on a rising plane of nutrition for each program, and keeping them on a maintenance ration between programs. In practice, this means providing the best possible feed to the donors from one week before the program begins until the collection day.

SUPEROVULATION AND SYNCHRONIZATION

During the superovulation and heat detection periods, it is very important to allow for enough time to carry out all aspects of the program at the times indicated in the program.

- All injections should be given intramuscularly in the hip or the muscle of the hind leg using a 1 1/2 inch needle. Shorter needles do not place the drug adequately into the muscle.
- Use one syringe for prostaglandin (e.g., Estrumate) and another for the superovulation hormones. Do not mix syringes.
- For cows working off a natural heat, the time from the first hormone injection to embryo collection is 12 days. Please inform us of the date the donor was in heat at the time of your phone call to schedule a visit to examine your donor.
- If we need to initiate a startup heat, the time from the first injection to collection is on average 24 days. The first step is to pre-synchronize the donors and recipients with an injection of prostaglandin (Estrumate or Lutalyse or EstroPlan to name a few).
- About 13 days after the first injection, or from 7 to 13 days after heat, the donors are superovulated with a 4-day injection program of the hormone FSH, given morning and evening. In the middle of this schedule, the donors and recipients are given an injection of prostaglandin to bring them into heat.
- The donors are bred two or three times, once ten to twelve hours after the start of standing heat, and again 12 hours later. If a donor is still in standing heat at the second AI, a third breeding should be applied 12 hours after the second AI.

HEAT DETECTION

Heat detection is one of the most important aspects of an embryo transfer program. The time that you invest in heat detection with both your donors and recipients will pay dividends in terms of more transferable embryos and better pregnancy rates in your recipients. In general, to best serve your program, any recipient that has not shown standing heat will not receive an embryo.

Check all animals for heat beginning one full day before the donors are due in heat and for two days after.

All heat checking should be done at first light, midday, at dusk, and at 11 PM to midnight. Please record the time of day and date that the recipients show standing heat.

THE DAY OF COLLECTION AND TRANSFER

Seven days after breeding, the staff of AVC/CPGC will come to your farm to carry out the embryo collections, embryo sexing, embryo transfers and if necessary embryo freezing. The day and date of the flush is shown on the donor program.

The morning of the flush we ask that you have the donor(s) safely and securely locked in preparation to be flushed with a nearby table or barrel on which to place our supplies. Recipients should also be ready to be palpated to determine their suitability to receive a transferred embryo.

Please also provide a copy of the donor’s registration information and a semen straw from the breeding or a copy of the breeding slip. Any first-time donors will need to have hairs pulled for parentage testing.

For farms in the Lower Mainland we will most often transport the flush materials to our laboratory for processing. In other locations we will require a clean room with a table for our portable laboratory.

RESULTS ACHIEVABLE USING EMBRYO TRANSFER

Results vary from farm to farm and program to program however, donors tend to respond similarly flush to flush. If your donor does not respond to hormones, or fails to produce viable embryos on her first try, we can modify her program on a subsequent super-ovulation and quite often achieve good results.

The following figures are averages only, and do not constitute a guarantee of results. That being said, on average, 6 viable embryos can be collected from each flush (range 0-60). This generally achieves a 75% pregnancy rate with fresh transferred embryos. Sexed embryos show a similar fresh transfer pregnancy rate if the recipients are properly selected and managed.

Should you have more embryos than recipients, we will freeze the best embryos and transfer the rest to fill the suitable recipients.

Embryos can be frozen and stored indefinitely. Any manipulation of embryos including freezing can reduce the embryo survival rate, but because the best embryos are frozen, pregnancy rates are essentially identical to that of fresh embryos. Sexed frozen embryos show a slight drop in pregnancy rate compared to unsexed frozen embryos, however we consistently obtain satisfactory pregnancy rates with these embryos as well.

THE PAPERWORK

We electronically submit all required information for each embryo transfer event to the respective breed associations to allow for registration of the resultant calves.

We also file all the current embryo transfer forms for embryo recovery, embryo transfer, embryo freezing and embryo movement under your account for your future reference.

Embryo Transfer Menu

THE PROCESS