Hi Anne
I agree with you! First, it seems to me that as fat contains no fiber
and therefore as such does not produce the heat of digestion produced by
breaking down fiber, it would automatically qualify as a "cooler" feed
than any form of grain or hay. Second, two of the articles that
immediately jumped out of the literature were "Heat Production in Pony
Geldings Fed a fat-supplemented diet" JL Snyder, et al. Proceedings of
the 7th Equine Nutrition and Physiology Symposiums, pg 144, which stated
feeding fat increased energy digestibility and increased the energy
balance of the diet without a corresponding increase in heat production
(translation: the carbohydrate diet produced more heat than did feeding
fat).
Second study that sprang to hand was "Efficacy of a fat-supplemented
diet to reduce thermal stress and maintain muscle stores in exercising
Thoroughbred horses" BD scott, et al, Proceedings of the 12th ENPS,
1991, which stated horses fed a fat-supplemented diet had higher
concentrations of stored glycogen at rest and as well had a decreased
thermal load than horses fed a conventional grain-based diet.
Finally, I came across a study "The effect of supplemental fat on
exercising horses" LR Moser, et al, same publication that very clearly
and definitively states that horses fed a high fat diet (11%) do not
have a higher heart rate during intense submaximal exercise than horses
fed a conventioal hay/grain diet. A comment is also made that these
results are further supported by studies conducted by Pagan, et al and
Webb, et al.
These studies would all appear to disagree with Tom's feelings that "one
way to get higher heart rates in horses is to overfeed fat".
Susan Evans