When the Flush Underperforms: What I See on Transfer Day

The donor side of your ET program — superovulation, breeding, and collection — happens before I show up. By the time I arrive on transfer day, that work is done and the embryos are on the table. What I am evaluating is what came out: the grades, the count, the viability. Sometimes what I see does not match what the program was supposed to produce.

The grading scale in practice

Embryos are graded on a 1 to 4 scale. Grade 1 is excellent — symmetrical, compact morula or blastocyst, appropriate cell mass for the developmental stage. Grade 2 is good, with minor irregularities that do not compromise viability. Grade 3 is fair, with visible defects that leave the outcome uncertain. Grade 4 is poor or degenerate — not a transfer candidate.

Most programs targeting frozen embryo transfer work with Grade 1 and Grade 2 embryos. Frozen-thawed embryos have already survived cryopreservation, which functions as a quality filter — fragile embryos do not survive the freeze-thaw cycle at the same rate as stronger ones. When I see a Grade 3 in a frozen batch, it is there because someone made a judgment call at collection that it was worth trying. Sometimes they are right.

The decision on transfer day

When I have a Grade 2 or a borderline Grade 3, the decision is not purely about the embryo — it is about the recipient pairing. If the recipient is ideal: correct BCS, good CL on ultrasound, clearly synchronized, I will transfer a Grade 2 without much hesitation. If the recipient herself is marginal, I am not committing a borderline embryo to her. I would rather hold the embryo than lose it to a poor match.

I make this call in real time, in the chute, with the producer standing there. The conversation goes better when the producer understands the grading criteria before transfer day starts.

A Grade 3 embryo in a textbook recipient is worth trying. A Grade 2 embryo in a marginal recipient is not a transfer I feel good about. The embryo grade and the recipient quality are not independent variables.

What the flush result tells me about upstream decisions

I am not doing the donor work, so I am reconstructing what happened from what I receive. But the patterns are consistent. Donor body condition coming into superovulation matters — a cow that was losing condition through her superovulation protocol was working from a disadvantage before the first injection. Stress around handling and injection timing affects response. Semen quality on breeding day is a variable that does not always get enough attention: suboptimal post-thaw motility compounds whatever the donor contributed.

Weather is a real factor in Southeast programs, especially summer flushes. Heat stress in the week before superovulation affects follicular development and oocyte quality before anyone knows there is a problem. By collection day, the window for correcting it has passed.

How I handle a difficult transfer day

Honest, specific, and before we start moving cattle. Here is what we have, here is what I think each embryo's chances are, here is the decision I would make on each one and why. If the program yielded two Grade 1 embryos instead of eight, that is not a good day — but it is not automatically a failed program. One option is to proceed with what you have. Another is to regroup, look at what the donor management looked like leading into this cycle, and plan accordingly.

What I try to avoid is the conversation at the end of a bad transfer day where the producer is surprised. The grade distribution is visible before the first embryo goes in. If it is going to be a hard day, the producer should know that before we start.