Many semi-rural dwellers keep sheep, so it might help to understand the digestive system of sheep. They belong to the ruminant classification of animals. There are about 150 different domestic and wild ruminant species including cows, goats, buffalo, antelope and giraffe.
Sheep are grazers, so they eat grass and leafy plants. Forbs, which are broad leafed, non-woody plants, are their favourite food.
Ruminants are described as having “four” stomachs and “cud-chewing” behaviour. The cud is a soft, rounded ball of food that has been regurgitated. Regurgitation refers to when undigested or partially digested food is brought back up from the stomach to the mouth, where it is chewed again.
The primary difference between ruminants and simple-stomach animals, such as humans, dogs and pigs, is the presence of a four-compartment stomach. The four parts are the rumen, reticulum, omasum, and abomasum. So the digestive system of sheep is complex.
Four-part stomach
Often it’s said that ruminants have four stomachs. In reality, their “stomach” has four parts.
The rumen occupies a large percentage of the abdominal cavity of the ruminant. It is a large storage space for food that is quickly consumed, then later regurgitated, re-chewed, and re-swallowed in a process called cud chewing. Rumination or cud chewing occurs primarily when the animal is resting and not eating. Healthy mature sheep will chew their cuds for several hours each day.
The rumen is also a large fermentation vat. It contains billions of microorganisms, including bacteria and protozoa. These enable ruminants to digest fibrous feeds such as grass or hay that other animals cannot efficiently make use of.
Fermentation in the rumen produces enormous quantities of gas. Sheep belch once every minute, which they do silently. If the belching stops the stomach swells with gas. We call this bloat. Mild cases of bloat can usually be successful treated with an antacid.
The reticulum is closely associated with the rumen and the contents mix continually between both sections. This part of the digestive system looks like a “honey comb” in appearance. The reticulum is connected to the spherical omasum by a short tunnel.
Relatively little digestive activity occurs in the omasum.
Final stage of digestion
The first three stages of digestion can be described as mechanical, whereas when the food reaches the abomasum, chemical digestion starts to take place. The abomasum is the “true” stomach of the ruminant. It has a similar function as the stomach of a non-ruminant. This is where secretion of enzymes and acids breaks down nutrients, which are then absorbed into the blood.
Sheep tend to eat on the morning, chew the cud into the afternoon and eat again in the late afternoon.
Smallholders cannot presume that pasture grass is enough for sheep. Their feed needs to be supplemented by a small amount of pellets to ensure complete nutrition. Like all livestock, sheep need protein, minerals, trace minerals and vitamins, as well as sufficient carbohydrates.