Effect of Dietary Fat Type on Muscle Glycogen in Horses
by AMANDA GRIMMETT
(Taken from: Grimmett, A. 2006, Effect of dietary fat type on muscle glycogen in horses. Proc. Australian Equine Science Symposium, 1 p25.)
Numerous studies involving feeding fats to working horses have reported advantages relating to glycogen storage, sparing and utilisation in skeletal muscle. Horses consuming high fat diets apparently employ fatty acid oxidation to meet energy needs during sub-maximal (aerobic) exercise, thereby sparing glycogen in skeletal muscles. Increases in utilisation of muscle glycogen during high intensity (anaerobic) exercise have also been observed in fat-supplemented horses. This has implications such as delaying time to onset of fatigue and increased performance during high intensity exercise.
However, some studies have reported no such interactions between fat supplementation and skeletal muscle glycogen status. This inconsistency may be partially attributable to the types of fat fed in test diets.
Table1: Muscle glycogen storage and utilisation in horses fed different types of fat in various experiments.
Studies in which animal fat (highly saturated fat, rich in long and medium chain fatty acids) was fed, consistently resulted in increased resting muscle glycogen concentrations and increased glycogen utilisation during high intensity exercise. This was not the case in studies where corn oil and soybean oil (both long chain, polyunsaturated fats) were fed.
Fats fed to horses vary significantly in their lipid biochemistry, even at the most basic level. Few studies have explored the impacts of degree of saturation and fatty acid chain length on variations in glycogen storage and utilisation in skeletal muscle.
Results indicate that glycogen-related ergogenic benefits may be more reliably observed when a saturated fat containing medium chain fatty acids is fed. Like animal fat, coconut oil is highly saturated with a high content of medium chain fatty acids. Consequently, it may yield similar glycogen-related benefits, as well as being highly palatable and easily obtainable.
Eaton, M.D., Hodgson, D.R., Evans, D.L., Bryden, W.L., & Rose, R.J. 1995, Effect of a diet containing supplementary fat on the capacity for high intensity exercise. Equine Veterinary Journal., Supplement, 18 pp.353-356.
Harkins, J.D., Morris, G.S., Tulley, R.T., Nelson, A.G., & Kamerling, S.G. 1992, Effect of added dietary fat on racing performance in thoroughbred horses. Equine Veterinary Science, 12(2) pp. 123-129.
Hughes, S.J., Potter, G.D., Greene, L.W., Odom, T.W., & Murray-Gerzik, M. 1995, Adaptation of thoroughbred horses in training to a fat supplemented diet. Equine Veterinary Journal., Supplement, 18 pp.349-352.
Julen, T.R., Potter, G.D., Greene, L.W., & Stott, G.G. 1995, Adaptation to a fat-supplemented diet by cutting horses. Journal of Equine Veterinary Science, 15(10) pp.436-440.
Oldham, S.L., Potter, G.D., Evans, J.W., Smith, S.B., Taylor, T.S., & Barnes, W.S. 1990, Storage and mobilisation of muscle glycogen in exercising horses fed a fat-supplemented diet. Journal of Equine Veterinary Science, 10(5) pp.353-359.
Orme, C.E., Harris, R.C., Marlin, D.J., & Hurley, J. 1997, Metabolic adaptation to a fat supplemented diet by the thoroughbred horse. British Journal of Nutrition, 78 pp.443-458.
Scott, B.D., Potter, G.D., Greene, L.W., Reagor, J.C., Webb, G.W. & Webb, S.P. 1989, Growth and feed utilisation by yearling horses fed added dietary fat. Journal of Equine Veterinary Science, 9(4) pp.210-214.