Vet wrong about ultrasound

[drmatthewtaylor]

Hi Dr Taylor, I have a question perhaps you can answer..... The wee foal 120 tests for estrone sulfate. The company advises not to use past 300 days as a false negative can occure due to drop in estrone sulfate as mare nears foaling. Ive read a few articles suggestion this drop can also cause false negatives in a blood estrone pregnancy test. My question is, how close to foaling? in a few days or a month? And would it drop so low as to appear negative, say a month out from foaling?

Estrogen levels drop at day 280.

 

[Bonny]

Thank you so Much Dr Taylor, and would they drop to a non pregnant level?

 

[drmatthewtaylor]

Thank you so Much Dr Taylor, and would they drop to a non pregnant level?

I have never run a Wee Foal and I do not know about it's range, sensitivity, or specificity.

In general estrone tests; whether they be blood, milk, or urine, are considered confirmatory tests for pregnancy rather than early detection. Ultrasound can diagnose pregnancy nearly 3 weeks earlier than any of these tests. Gestation in the mare averages 11 months, so getting mares pregnant early is important otherwise after a few years a mare will have to be left open because she foaled 'too late'. The cost of early ultrasounding would outweigh the failure to return to pregnancy and avoid that year off.

It could be economically feasible to use estrone tests later in pregnancy to confirm that the pregnancy was maintained. I would encourage owners to run those tests 3 times during pregnancy.

1) 30-40 days gestation to confirm the embryo held.

2) 2 weeks prior to the end of the breeding season, so any open mares could be recycled and bred for that year.

3) October , so any open mares could be placed under ligts for early breeding next year.

If this protocol is run then there should be no reason to run a nearly 300 day confirmatory test, as by that time pregnancy would be well established and foaling dates would be well estimated.

If I purchased a mare that was supposed to be in foal then I would ALWAYS have her palpated both before and after purchase to confirm pregnancy as I not only consider palpation/ultrasound to be more accurate, it also involves another layer of culpability that estrone tests simply do not.

Dr. Taylor

 

Thank you again Dr. Taylor. That's exactly what my equine vet did for me. We U/S each mare 3 times during her pregnancy for all the reasons you gave! I had my most successful seasons following that regime. Thank you again!

 

[Bonny]

Agreed Diane, Thank you so much Dr Taylor!