Stroll past any magazine display or newsstand and chances are some health or lifestyle cover is boasting of new ways to boost your metabolism. The term "metabolism," however, encompasses far more than simple weight gain, weight loss, or calorie burning. Whether in humans or horses, it refers to chemical reactions occuring within the body that ultimately provide it with the components required to sustain life.

The metabolic process typically is divided into categories: Anabolic reactions use energy to build structural components of the body such as muscle. Catabolic reactions break down large particles to smaller particles and produce energy. Many anabolic reactions occur just after feeding, with the body storing and building substrates for later use, while catabolic reactions tend to occur several hours (or days) after a meal, or with exercise, when fuels need to be made available. Adenosine triphosphate (ATP) is the unit of energy the body uses. "Metabolic rate" refers to the total amount of energy a body uses at rest in a day (for tasks such as breathing, maintaining body temperature, etc.) and differs based on factors such as body size and horse breed.

Metabolic Reactions

Following a meal, the body of a horse at rest breaks down feed substrates within its cells and stores them for later use. Feeds high in starch and sugar (cereal grains) are ultimately digested into glucose, which is absorbed into the bloodstream. This increase in blood glucose concentration triggers the pancreas to release the hormone insulin, which allows glucose to leave the bloodstream and enter muscle or adipose (fat) tissue (among other body tissues), thereby returning blood glucose concentrations to baseline