WHY HERBIVORES DIET IMPOSES CERTAIN PROBLEMS FOR DIGESTION AND HOW SOME ANIMALS HAVE OVERCOME SUCH PROBLEMS
Herbivores are animals which eat only plants and no meat. This means leaves, flowers, fruits or even wood. Herbivores often do not have to search far to find food to eat. In some cases for example wood boring insects; they are entirely surrounded by their food. However the disadvantage for the herbivores is that it can be difficult to digest and is often low in nutrients. Sheep, horses, rabbits and snails are well known examples of herbivores which eat grass and leaves.
Herbivores can be classified as frugivores, which eat only fruit, and folivores, which specialize in eating leaves. The diets of some herbivorous animals vary with the seasons, especially in the temperate zones, where different plant foods are most available at different times of year.
They vary of diets in these classes of herbivores poses some problems. These problems are normally seen during digestion. Some of the animals are unable to digest completely the food they eat. Cellulose is another source of problem and it contains much of the energy. Since most of the herbivores digest food through enzymes, therefore it is difficult for the enzymes to broken down as it contains high organic substances. This cellulose composed of organic substances. only mechanical means such as extended chewing or fermetation can help to speed up the process of digestion.
Some animals have overcome these problems; most herbivores have tough mouth for chewing and grinding food. For example cattle have complex digestive system which contain micro organisms. These micro organisms play a role in breaking down of cellulose and other indigestible plant materials. These micro organisms help to turn the plant matter into nutrients that the animals can absorb.
Some herbivores are called ruminants (e.g. cattle, sheep and goats) which have two stomachs. They have two stomachs of which during the day, they chew their food in the same way as sheep. When they swallow in the food they go into the first stomach, called the rumen. During the evening the animal brings a mouthful of food back into its mouth from its first stomach and this is called regurgitating the food. During this process food is chewed and then swallowed into the second stomach.
The non ruminant (e.g. horse) herbivores depend on symbiotic micro-organisms for cellulose digestion. Their anatomical adaptations differ from true ruminants. Digestion of cellulose in the plant diet by microbial enzymes in adult cattle, sheep and goats on a normal diet occurs in the fore stomach, of which the rumen is the largest compartment; this organ therefore serves as the major source of energy in those species. Microbial fermentation is another way in which the herbivores adapted to make it simple for the digestion process. Therefore herbivores maintain continuous fermentation and absorption in their digestive tract.
Cellulose digesting enzymes called cellulases are present in the intestinal tract of several invertebrates that feed on wood and similar plant products. These enzymes are, however, absent for some reason from the digestive secretions of. Plant material is lower than meat in energy content, and the herbivore must consume a large quantity in order to satisfy its energy requirements.
Some animals have become large because of high metabolic process. These animals grew bigger in order for them to have a long digestive system that will allow a complete digestion for plants that are very very hard. Therefore they become larger in order for them to reach the plants matter that contains less cellulose.
1. The gastrointestinal system, an introduction [Internet] [cited 2006 May 15]. Available from: http://www.chu.cam.ac.uk/~ALRF/giintro.htm
2. Knowledgerush.com, Herbivore [Internet]. Knowledgerush.com, 2003 [cited 2006 May 15]. Available from: http://www.knowledgerush.com/kr/encyclopedia/Herbivore
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