Hi,
I've been a big fan of probiotics for about ten years now, back before
they were on the market for horses but were being commonly fed to dairy
cattle and feeder pigs. I've always thought they helped with keeping a
gut happy, because they increase the population of "bugs" in the gut.
Since stress contributes to killing off the little bugs that carry out
digestion and keep the mail moving, so to speak, it only makes sense
that starting a race with as many bugs as possible is going to help keep
the gut moving and working.
Also, I've noticed my horses recover from a ride much better when they
get probiotics afterwards (actually, I feed it continually, but more so
after a ride). Again, since stress of any kind like racing, trailering,
antibiotics, foaling, disease, whatever can knock down the bug
population, it makes sense to keep the bugs happy by replenishing the
supply.
Just my two cents.
Susan Evans