Agriculture Reference
In-Depth Information
abomasum is sometimes called the true stomach, because it functions in a way
that's most similar to that of single-stomached creatures, including humans.
Digestion in these latter parts is primarily a chemical process during which
enzymes break down the feed as it passes through.
The four-part stomach system allows ruminants to eat — and digest —
feeds that other critters can't take advantage of. Specifi cally, it enables them
to digest cellulose, which accounts for 50 percent of the organic carbon on
earth (but we can't digest it). Being able to digest cellulose enables sheep to
receive maximum benefi t from all the amino acids present in their feed.
The Final Phases of Digestion
The cecum and intestines are the fi nal places through which the feed passes.
These organs provide one last chance for some breakdown to occur through
both chemical and biological processes.
The small intestine is like Grand Central Station — it's the place where
most transfers occur. Available nutrients, which are now in their elemental
and molecular forms, change trains, switching from the digestive “track” to
the bloodstream, or the body's equivalent of a commuter train. This com-
muter system (veins, arteries, and capillaries) disperses the nutrients to points
throughout the body, where they disembark as needed, “feeding” the organs,
muscles, and tissues. The other function of the intestinal system is really
important: it controls disposal of the waste products that the body can't use.
Cud
One unique characteristic of ruminant digestion is that the animals have to
“chew cud.” Cud is a bolus of partially digested material that's regurgitated
into the mouth from the rumen. Unlike the fi rst chewing, which is quick,
cud is chewed very thoroughly and then reswallowed. This process serves two
purposes: it allows additional mechanical grinding and it provides a continu-
ous source of large amounts of saliva for the rumen, which helps maintain a
healthy environment for the fl ora. Cud chewing happens off and on during
the day; all together, it takes up about 6 hours on a daily basis.
Digestion in Lambs
At birth, lambs lack a fully developed rumen. In fact, at fi rst the rumen is
relatively small (25 percent of total stomach capacity) and the abomasum is
relatively large (60 percent). By the time the lamb is 4 months old, the rumen
is almost fully developed (75 percent of stomach capacity) and the abomasum
 
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