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[RC] Elytes - some recent references - PattiSweat losses [in endurance horses] have been estimated at 3-7% of body weight (Schott 1997, Barton 2003) [The 7% presumes intense work, hot humid conditions - this may vary by horse, fitness, etc.]
The sodium content of sweat has been estimated at 2.8g Na/L (Coen 2005) to 3.1g Na/L (McCutcheon 1995) (the 2007 NRC uses 3.1g Na/L).
A 900lb horse losing 7% BW (63 lbs, approx 28L) on ride day requires 96.8g of Na -- 33.6g to meet daily requirements of intense work plus an additional 63.2g to replace extra losses for that day. The total can be met by
8.6oz of salt (11.2g Na/oz salt) - 3oz as part of the normal daily requirement for training/weekly workload and an additional 5.5oz throughout the day for replacement of losses - which will also cover chloride reuirements/losses/replacement.
Similarly, potassium (K) sweat loss is approx 1.4g K/L (Coenen 2005) - replacement is figured at 2.8g K/L (allowing for 50% absorption). The daily requirement for the same horse/event is 100.5g of K -- 43.4g to meet normal daily requirements plus 57g replacement. The total requirement is easily met/exceeded if the horse is eating at least 10-12 lbs of hay/day; replacement during the day would be covered by 5lbs of hay during the day.
This presumes the horse has been having sodium (and other) requirements met on a daily/weekly basis - the daily requirement also accounts for endogenous losses. If higher sweat (weight) losses are know by actual weight using scales, the requirment for daily maintenance and replacement can be adjusted up accordingly. There's new and interesting stuff about sweat loss and elytes on IVIS - (you'll probably have to register but it's free)
Abstract - French Endurance Team performance without electrlytes (page 4)
Less potassium may be better? (Schott, page 15 same session as above)
Nutritional Management of Endurance Horses (Goer, U of Guelph)
(Also mentions K-free elytes as possibly being better)
and more articles (I searched on "sweat loss endurance horses") at IVIS http://ivis.org/.
What shows up consistently is the need for sodium (as in salt - NaCl) as almost all other "elytes" are already in abundance to excess in hay and forage, and questioning of giving additional potassium (K). You don't have to go crazy about the math (though if you do want to get anal about it I can send you a spreadsheet) - just have a flake of alfalfa and a box of salt handy.
Patti K
Vail AZ
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