An important question has come up in the discussion of (Warmblood) Fragile Foal Syndrome. It seems to be the case that not all foals positive for FFS are carried all the way to term. I think this is important because when you're evaluating the importance of FFS, it's good to keep in mind that many of the losses that breeders sustain due to FFS are hidden.

The question has come up because there is a discrepancy between the number of foals that we would expect to see and the number that are actually born with the disease. So how much do we know about the numbers?

I found some information about foals registered in Germany in 2012, so we can use that as an example to run some numbers. According to a German brochure on the horse industry, 39,000 foals were registered in Germany in that year. We have to assume there were more breedings than that, but we can use 39,000 as the number of breedings, because we know there were at least that many.

We can calculate how many breedings would have resulted in FFS/FFS foals. Here's the math:

We know that approximately 10% of the warmblood breeding population in Germany are carriers of FFS. We don't have an exact percentage, but it's about 10%, and it hasn't changed much since 2012. FFS was not tested for in 2012, so it was not a factor in breeding decisions. So the chance of breeding a carrier to a carrier was random, not influenced by knowledge of FFS. With over 39,000 breedings, small variations would even out, so it would have been very close to what we would expect from the math: approximately 1% (10% chance for the stallion to be a carrier, times 10% chance for the mare = 1%). In other words, approximately 1 in every 100 breedings would have been carrier to carrier. Of those, the chance of a FFS/FFS foal is 25%, and 25% times 1% = .0025 or 1 in 400. That's solid for the percentage of affected foals we could have expected in Germany in 2012.

Using 39,000 as the number of breedings, if we multiply that times the .0025 we get 97.5. So approximately 100 of those breedings would have produced foals that were FFS/FFS. That means one of two things: either there were around 100 foals born in Germany in 2012 that had to be euthanized due to the symptoms we're familiar with for FFS - or something else happened to those foals. Those are the only two options. Either that many were born and died, or that many were bred but didn't reach term.

We'll probably never know what percentage of those were born and euthanized, and what percentage were resorbed or aborted or never conceived. It seems hard to believe that 100 foals could have been born and died a horrific death each year in Germany - plus others in other countries - and no one noticed or commented on it. It's more likely that the large majority never reached term.

But we do know that approximately 100 breedings were lost to FFS in Germany in 2012 alone.

Many breed registries and large breeding operations around the world are wrestling with the issues around FFS. As they calculate the importance of FFS to breeders, they may be thinking, "We have almost never seen a dead FFS foal. It's tough for the breeder this happens to, but it's just not that big a deal." If decisions are being made on that basis, they're likely to be wrong, since it's not the full story. The full story is not just a handful of dead foals. From the math, the dead foals are just the tip of the iceberg. The losses are much greater than that.

It's hard to calculate the monetary loss. There's a big difference in associated costs between a mare not conceiving, and a mare carrying a FFS/FFS foal to term only to have the foal put down after birth. But it's time to start factoring in these "hidden" losses due to FFS.

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