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RE: [RC] [RC] Riding strategy -- mare in heat at an endurance ride - Susan E. Garlinghouse, DVM

My understanding from scads of recent reading (because I just did a lecture
on it a few weeks ago) is that a lot of the rumors about estrus and tying up
is because there is a higher reported incidence of recurrent exercise
rhabdomyolysis (that's the early onset form) in two-year-old, nervous, goofy
TB or STB fillies on the racetrack on rations sky-high in grain.  So they
think there *might* be some relationship to hormonal cycles, but it hasn't
been clearly demonstrated, and it certainly isn't more than AT MOST a
contributing factor in mares that are already prone to it.  There are tons
of other factors that can also cause symptoms of tying up, including
exposure to viruses, diet, some specific mineral issues (including
selenium), and genetic relationships in calcium channel abnormalities
specifically in the TB breed, or abnormal glycogen synthesis in mostly the
quarter horse breeds.

Also, remember that most of the research in RER is still from the race
tracks, because there's a significant prevalence of the issue on the tracks
and any lameness issue means loss of potential earnings---so that's where
the research money is focused.

There are a lot of different factors that can all show up as "tying up" but
have very different causes.  Early onset tying up certainly does occur in
endurance horses, but most of them still present in the PS region as the
later version more related to exhausted horse syndrome.  In those cases, I
haven't seen any higher prevalence between one sex over another, which I
suspect is similar to what Heidi has seen in the PNW.

JMO.
Susan Garlinghouse, DVM

-----Original Message-----
From: ridecamp-owner@xxxxxxxxxxxxxxxxx
[mailto:ridecamp-owner@xxxxxxxxxxxxxxxxx] On Behalf Of heidi@xxxxxxxxxxxxxxx
Sent: Sunday, February 10, 2008 7:23 PM
To: Beth Leggieri
Cc: Nancy Sturm; ridecamp@xxxxxxxxxxxxx
Subject: RE: [RC] [RC] Riding strategy -- mare in heat at an endurance ride

More than behavior issues, I am concerned about the physiological changes
that occur which can get them into trouble if their bodies are
stressed--which an endurance ride certainly does.  Specifically the tendency
toward azotoria seems to be connected to their heat cycles (resulting in
their decreased ability to deal with excess lactic acid).  


I personally think this is more an individual problem than a "mare" problem.
When a mare ties up, people say, "Oh, it's a mare!"  When a gelding or a
stallion tie up, they say, "Oh, well, he tied up..."  I don't know of any
evidence that they have any such decreased ability to deal with excess
lactic acid--never mind that endurance horses don't tend to build up lactic
acid anyway.  Sure, you can fail to warm them up (regardless of gender) and
slam into the first vet check and tie up--but that happens to geldings and
stallions, too!

Heidi

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Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp
Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp

Ride Long and Ride Safe!!

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RE: [RC] [RC] Riding strategy -- mare in heat at an endurance ride, heidi