Final answer:
The stomach of an adult horse comprises less than 10% of its total digestive tract, as the herbivore's digestive system is uniquely adapted, with a longer intestinal tract, to process plant material effectively.
Step-by-step explanation:
The proportion of the total digestive tract capacity that the stomach of an adult horse makes up is less than 10%. Horses are herbivores and have a unique digestive system to process bulk and fibrous plant material effectively. Despite the stomach's ability to expand, it is relatively small compared to the rest of the digestive system, especially the large intestine, which acts as a fermentation vat and is vital for digesting roughage.In contrast to horses, the majority of fat digestion in most animals occurs in the small intestine where bile acids and pancreatic enzymes catalyze the breakdown of fats. Considering the anatomy of herbivores, they typically have longer intestinal tracts, which provide more time and surface area to break down the cellulose in plant material.