Feeding equine animals involves obtaining an equine feed combined with a yeast fermentation product such as a Saccharomyces cerevisiae fermentation product, and feeding the feed to the equine animal such that ingestion causes the equine animal to improve performance, including a mitigated inflammatory response or an increased immune in function. The feed may contain about 0.1 to 1.0 percent of the yeast fermentation product by weight of the feed. A formulated feed ration for the equine animal may include grain- and forage-based feed and a Saccharomyces cerevisiae fermentation product in an amount of about 5 grams to about 40 grams per head per day.