011 The Effect of Various Levels of Dietary Starch on Glycogen Replenishment in the Light Working Horse

• Published in: Journal of animal science 2016-12, Vol.95 (suppl_1), p.06-06
• Main Authors: Phillips, C. A., Cavinder, C. A., Sigler, D. H., Fluckey, J. D.
• Format: Article
• Language: English
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/ssasas2017.011

Abstract Multi-day competitive events throughout the performance horse industry brings forth the necessity to understand recovery from exercise, especially from bouts of intense, anaerobic exercise. A recent trend of high fat, high fiber diets is promoted as a safe way to increase the energy density of a diet. This complicates the issue of fatigue and recovery as anecdotal evidence has shown that horses on a high fat, high fiber diet may fatigue during multi-day competitions faster than horses on traditional diets. Nine Quarter Horses (2 to 7 yr; 409 to 494 kg BW) were used in a 3 × 3 Latin square study lasting 105 d to determine the effect of various levels of dietary starch on glycogen replenishment in the light working horse. Horses were fed 1% BW/d in Coastal Bermudagrass hay with remaining calories met by a high starch (1,206.67 g/d)(HS), medium starch (844.61 g/d)(MS), or low starch (263.13 g/d)(LS) concentrate. After a 7 d washout period, horses were transitioned to 1 of the 3 diets over 7 d for a 14 d treatment period where they were then worked to fatigue in a standardized exercise test (SET). Horses were lightly exercised for 30 min 3 d/wk. The SET consisted of a 30 min trot in a panel exerciser, followed by 27 min of an incremental high-intensity work on a treadmill. Skeletal muscle was biopsied from the biceps femoris at rest, immediately after the SET, and 24 and 48 h post exercise. Samples were submerged in liquid nitrogen and stored at -80°C until glycogen analysis using a commercial kit. Venous blood samples were taken at rest, immediately post exercise, 10 min after recovery, and 24 h post exercise. Data was analyzed using Proc Mixed (SAS) program with fixed effects of period, treatment, and time × treatment with horse included as a random block effect. High starch had higher resting muscle glycogen concentration (P = 0.009) than MS (10.25 vs. 8.28 μg/mg wet wt) (Figure 1). Low starch had higher glycogen concentration 24 h post (P = 0.04) than HS (9.52 vs. 7.68 μg/mg wet wt). High starch utilized more glycogen than MS or LS. A slight reduction in glycogen post exercise for MS and LS indicated that fat or protein may have been used as substrate for exercise. Results indicated that feeding the HS diet did not yield an advantage in recovery time over a MS or LS diet.