Equine Performance & Stamina; Achieving Optimal Results

The performance of an equine athlete is vitally important whether if we are talking Dressage, Jumping, Western Pleasure, Barrel Racing or on track TB or QH racing. One of the biggest determinants of performance is stamina.  Without stamina, almost always, performance is reduced on various levels.  So, what determines one or the other? What dictates performance in that equine athlete and considering that stamina is involved, what options do we have to improve the outcome?