Biodiversity

Friday, May 12, 2006

HERBIVOROUS DIET "IMPOSES" CERTAIN PROBLEMS FOR DIGESTION

Herbivores are animals that feed only on plants. These are animals like rabbits and elephants. Some of the herbivores eat a certain part of the plant. "Herbivores are further classified into various sub-groups such as frugivores and folivores. Frugivores are animals that feed only on fruits whreas folivores specialise in eating leaves. Most of the fruit and leaf eaters also eat other parts of the tree such as roots and seeds. The diet of herbivourous differ s according to the season "(1). There are some seasons at which plants loose some leaves, so the folivores will have to change their diet for that period until the leaves develops again.

The problem that herbivores face with their digestion is caused by cellulose.Their diet contains a lot cellulose because plant cells are made up of cellulose. Enzyme cellulase is used for the breaking down cellulose, so it is difficult for cellulose to be broken down due to the fact that it contains high organic substances. In some vertebrates enzyme cellulase is not present in the digestive secretions of some vertebrates and these vertebrates digest cellulose and depend on it as their source of energy. They behave like this because inside their gut there are symbiotic micro-organisms which can digest cellulose. Animals like ruminants solve this problem esily. Ruminants are those animals with stomach having "four chambers rumen, reticulum,omasum and abomasum"(2). Most ruminant animals include cattle, sheeps and goats and these are animals provide us with meat and milk. Ruminants chew their food during the feeding and when they are at leisure the food comes back to the mouth and they rechew it again. By doing this they are helping on breaking down of cellulose.

"In rumens extensive microbial fermentation of the plant diet occurs in a specialized region of digestive tract prior to digestion by alimentary enzymes. Some of the non-ruminant animals depend on symbiotic micro-organism for the digestion of their cellulose. Non -ruminant herbivores have large stomach with several compartments. The digestion of ruminants and non- ruminants is very similar, the only exception is that in non- ruminants there is no regurgitation and rechewing of food. The major fermentation of cellulose in herbivorous mammals takes place in a large diverticulum from the caecum. Microbial fermentation in caecum is similar to fermentation in the rumen"(1). The only difference is found by comparing the faeces. The faeces of the ruminants (taking cattle as an example), are watery and smooth, whereas the faeces of the non- ruminants (horse) have coarse fragments of food.

It is true that animals with high metabollic process grow very fast as in case with herbivores who eat cellulose. In order to solve this problem some animals just grow massively. The advantage is that they will have a long digestion which will allow them to digest tougher plants. This allows larger herbivores to protect themselve by their body size from predators and they feed on higher foliage while small herbivores are feeding on small grass. Most of the predators fear to attack them.Everything that the herbivores eat have a great impact on the structure of their body. The body size help them to have acess to all the types of the plants. Taller herbivore will depend on taller plants and shorter herbivores will feed on sort plants and grass so there is a balance.

Reference

1. Findlay, A.L.R. 1998 The Gastrointestinal System: an introduction Carnivores, Omnivores and Herbivores [Internet] 2006 May 11; 10:33 UTC [cited 2006 May 11] Available From:
http://www.chu.cam.ac.uk/~ALRF/giintro.htm


2. Wikipedia Contributors. Ruminant. Wikipedia, The free Encyclopaedia, [Internet] 2006 May 12; 11:10 UTC [Cited 2006 May 12] Available From:
http://en.wikipedia.org/w/index.php?title=Ruminant&oldid=49674058.

Dianah Nangammbi
Cilla CSIR
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Pretoria
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Tel: +27 12 841 2133
Cell: +27 73 121 3589
Email: dnangammbi@csir.co.za
http://wwwdianah.blogspot.com/

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