What distinguishes a horse's liver from that of other mammals?

Horses have a unique digestive system compared to many other mammals, and one significant distinguishing feature is the absence of a gallbladder. The gallbladder typically serves as a storage reservoir for bile produced by the liver, which helps in the digestion of fats. In horses, bile is secreted continuously into the small intestine rather than being released in bursts when food is consumed. This continuous flow aligns with the horse's natural feeding behavior, where they graze and eat small amounts of food throughout the day.

The lack of a gallbladder means that horses must rely on the constant secretion of bile to aid in nutrient absorption, particularly fats, as they digest a fibrous diet. This physiological adaptation is crucial for their health and digestion because it allows for a steady processing of the forage they consume.

In contrast, many other mammals have gallbladders that allow them to store bile and release it when needed, leading to a more intermittent and less constant secretion of bile as food is ingested. This is what sets the horse's liver functioning apart from that of other mammals.