How is a sheep biologically adapted to its way of feeding?

Answer 1

Sheep, like other ruminants, have a stomach with 4 compartments. These are the rumen, reticulum, omasum, and abomasum. The rumen is the largest of the four and is essentially a big fermentation vat (30-50 gallons in a cow, smaller in a ewe). It is where a bolus of food goes first after being swallowed, and it contains millions of microorganisms that are capable of turning the cellulose in forage into volatile fatty acids (VFA's) that are absorbed from the rumen and converted into energy. This fermentation process is the reason that ruminants can live on a grass diet. The reticulum is sometimes referred to as the 'pace-setter'. It is located in the cranio-ventral (lower front) aspect of the rumen, and is a small muscular pouch that contracts periodically to cause regurgitation of a food bolus. When ruminants are at rest, they will regurgitate these boluses, chew on them for a while, and swallow them back down. This is what people are talking about when they say that a ewe or cow is 'chewing her cud'. The omasum is a ball-like structure (about the size of a volleyball in cows, Baseball in ewes) that is filled with layer-upon-layer of absorbent leaves of tissue. Some people refer to the omasum as the 'many-plies' or the 'butcher's bible' because when you see one in cross-section it looks like pages of a book all stacked-up next to one another. This structure results in a very large amount of surface area, which helps the omasum do its job of absorbing water. The abomasum is the final compartment that food travels through before it gets emptied into the small intestine. The abomasum is most similar in structure and function to the stomach of monogastric animals - like pigs or humans. Some final break-down of proteins and carbohydrates occurs here to enhance absorption in the small intestine. Sheep and goats do an exceptional job of absorbing water in their large intestines, resulting in the production of pelleted feces. Cows are not nearly as efficient at this, and consequently they make a bigger mess!