Thursday, June 27, 2013

Overhydration?

I read this post from Boots and Saddles with interest.  Mel talks about her experience with crewing and gives her recommendations for both riders and crew members.  One of the things she mentions is her tendency to get overhydrated, which may have more to do with electrolyte imbalance than simply drinking too much.  While she is talking about drinking too much water as a person, I also got to thinking about whether horses can get overhydrated.

Every book I've read on endurance riding emphasizes the need for your horse to learn to drink as much as possible.  Yet, drinking too much water can be a really bad thing - almost as bad as not drinking enough.  Interestingly, a book called Fiber Menace spends an entire chapter talking about the repercussions of drinking too much.  The author, Konstantin Monastyrsky, lists the following as some of the lesser problems associated with drinking too much water: edema, fatigue, migraines, and nausea.  Long term overhydration can cause constipation, kidney disease, urinary disorders, digestive disorders, dengenerative bone disease, premature aging, muscular disorders, unstable blood pressure, and heart disease (see Ch. 2).  And he confirms what Mel says about thirst being a good indicator of needing to drink.  But that (much like Mel's experience) you need to be careful because the more you drink, the thirstier you get, so over time, thirst may not be a great indicator.

So how much water does a person need?  Mr. Monastyrsky says generally that people need 1.4-1.6 liters (or 5-7 glasses), but that amount includes water, anything else we drink, and food.  So you might only need to actually drink 2-3 glasses of water a day if you're eating a lot of moist food or drinking things besides water.  He does point out that things like physical activity and the environment can increase our water requirements, though.

What does this mean for my horse?  I did a couple of internet searches on overhydration and water intoxication in horses and couldn't find much aside from some articles on how some wild horses had died after a roundup from water intoxication.  I've read that horses drink anywhere from 5-15 gallons a day, depending on how much they are working and the ambient temperature.  My horse actually drinks from automatic waterers at the barn he is at now, but when he was at a self-care stable and I filled his water buckets, I remember him drinking probably 7-12 gallons a day, depending on work and the weather.

One of my concerns as I've started conditioning him is that he rarely drinks water outside of his stall or paddock.  I have been on rides in the past where he has drunk quite a bit out of a tank or stream, but he was working extremely hard and it was really hot.  I've been trying to figure out how much I should be working with him on drinking, and after reading Mel's post and rereading Fiber Menace, I'm beginning to think that I should stop worrying about it and just let my horse drink when he is thirsty.

I do always give him a mash after a ride that includes my own electrolyte mix of sea salt and trace minerals, so I'm hoping that the mash will help both with hydration and the replenishment of electrolytes.  My reading indicates that a big part of the problem with drinking too much water is that it flushes important minerals out of your system without replacing them, so theoretically, making sure that water is accompanied by salt and other minerals should help the body stay hydrated in the right way.

I should insert a huge disclaimer here.  I am not a vet.  I am not a doctor.  I'm not even a competing endurance rider yet, so my thoughts here are just that - thoughts.  Please do your own research and if you find something that provides some guidance on this topic, feel free to comment on this post, so others can see what you've found out.  One thing I've learned over the years is that nutritional advice is constantly changing and some topics are quite controversial, so it's important to keep researching and learning.

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