Horses, as herbivores, have a unique digestive system that allows them to extract nutrients from fibrous plants. Unlike humans, horses can thrive on a diet of grasses and other tough plant material thanks to a process called hindgut fermentation. This process involves specialized bacteria that break down cellulose, the main component of plant cell walls, into usable energy.
How Do Horses Digest Fibrous Plants?
Horses are classified as hindgut fermenters, meaning they digest fibrous foods through bacterial fermentation in the cecum and colon. Here’s a more detailed breakdown:
- Mouth: Digestion begins in the mouth, where the horse chews the plant material, breaking it down into smaller particles.
- Stomach: The chewed food travels to the stomach, which is relatively small in horses compared to other herbivores. The stomach’s capacity is only about 8.5% of their entire digestive system.
- Small Intestine: From the stomach, the food moves into the small intestine, where enzymes further break it down, and nutrients are absorbed into the bloodstream.
- Cecum: The undigested food residues then enter the cecum, a large pouch located at the beginning of the large intestine. This is where the magic of hindgut fermentation happens. Bacteria in the cecum ferment the indigestible residues, producing short-chain fatty acids.
- Large Intestine (Colon): The short-chain fatty acids are then absorbed in the large intestine, providing the horse with a valuable energy source. The primary function of the large intestine is to absorb water.
Why Hindgut Fermentation?
Hindgut fermentation allows horses to extract energy from plant material that would otherwise be indigestible. The bacteria in the cecum break down cellulose into volatile fatty acids, which the horse can then absorb and use for energy. This process is less efficient than the foregut fermentation used by ruminants like cattle but allows horses to be more athletic.
Ruminants vs. Hindgut Fermenters
| Feature | Ruminants