WHAT IS A RUMINANT?
Part of the sucess in raising and keeping sheep is understanding how their systems work. Many problems that crop up are associated with feeding. If you understand how their unique stomachs work, you have a better chance of preventing a problem. Again thanks to Susan Schoenian of the University of Maryland Extension for all of the valuable information. You can find her web sites at www.sheepandgoat.com. It is the best site you will ever find on sheep and goats.
Sheep belong to the ruminant classification of animals. Ruminants are characterized by their "four" stomachs and "cud-chewing" behavior. The cud is a food bolus that has been regurgitated.
There are about 150 different domestic and wild ruminant species including cows, goats, deer, buffalo, bison, giraffe, moose and elk. Ruminant animals are further classified by the foraging behavior: grazers, browsers, or intermediate grazers. Grazers, such as cattle, consume mostly lower quality grasses while browsers such as moose and mule deer stay in the woods and eat highly nutritious twigs and shrubs. Intermediats, such as sheep, goats, and white tail deer, have nutritional requirements midway between grazers and browsers. Of this group, sheep are more of a grazer, while goats and deer are browsers.
The primary difference between ruminants and simple-stomach animals (called monogastrics), such as people, dogs, and pigs is the presence of a four-compartment stomach. The four parts are the rumen, reticulum, omasum, and abomasum. Often it's said that ruminants have four stomachs. In reality, their "stomach" has four parts.
Camelids (llamas and alpacas) are called "pseudo-ruminants" because they have a three-compartment stomach instead of four like ruminants. Horses are not ruminants. They have an enlarged cecum that allows them to digest fibrous materials. Animals of this type are called "hind-gut fermenters." A rabbit has a similar digestive system.
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, which allow ruminants to digest fibrous feeds such as grass, hay, and silage that other animals cannot efficiently utilize.
Fermentation in the rumen produces enormous quantities of gas that ruminants get rid of by belching (burping). Anything that interferes with belching is life threatening to the ruminant and may result in a condition called bloat. Mild cases of bloat can usually be successful treated with an antacid.
The reticulum is closely associated with the rumen. Contents mix continually between both sections. The reticulum looks like a "honey comb" in appearance. Relatively little digestive activity occurs in the omasum. It is called "many piles" because it contains many layers of tissue. The abomasum is the "true" stomach of the ruminant. It has a similar function as the stomach of a non-ruminant: secretion of enzymes and acids to break down nutrients.
At birth, the lamb's rumen and reticulum are not yet functional. As lambs begin to nibble on dry feeds, these two compartments become inoculated with microorganisms. As the microbes multiply and begin to digest feed, they stimulate the growth and development of the rumen and reticulum. The lamb's rumen and reticulum are usually functional by the time the lamb is 50 to 60 days old.
Because lambs are not born with a functioning rumen, supplemental feeds such as creep feed, need to be highly digestible. Creep rations typically consist of feedstuffs that have been cracked, rolled, ground, or pelleted. Creep feeding enhances development of the rumen in the young lamb.
Though ruminants can digest grain (starch), their more natural diet is forages: grass, weeds, browse, hay, and silage. If too much grain is consumed at one time by the ruminant, a large amount of lactic acid is produced in the rumen and the pH of the rumen drops. This can be a fatal condition to the ruminant animal. Grain must be introduced slowly to the diet of ruminants to give the rumen time to adjust.
Sheep "love" the taste of grain. It's like "candy" to them. They will overeat if grain consumption is not regulated. If grain is slowly introduced to the ruminant's diet, grain can be supplemented and in some cases replace some of the forage in the diet. Whole grain is better for sheep because it requires them to do their own grinding of the grain. Digestive upsets are less common with whole grain as compared to processed grains (ground, rolled, or cracked).
Some forage should always be fed to ruminants to keep their rumens functioning properly and to keep them content.
One of the global impacts of ruminant livestock production is that when ruminants belch, they produce methane, one of the greenhouse gases. A small amount of methane is also produced by manure. Scientists are currently study ways to reduce methane production from ruminant livestock. For example, it is known that livestock fed certain plants produce less methane. Australian scientists are testing a vaccine to reduce methan production. "Fart" taxes have been proposed to help fund the research. They have not been implemented.