Herbivores have special adaptations for digesting cellulose

Cellulose is the principal organic compound in the diets of herbivores. Most herbivores, however, cannot produce cellu-lases, the enzymes that hydrolyze cellulose. Exceptions include silverfish (insects well known for eating books and stored papers), earthworms, and shipworms. Other herbivores, from termites to cattle, rely on microorganisms living in their digestive tracts to digest cellulose for them.

The digestive tracts of ruminants (cud chewers) such as cattle, goats, and sheep are specialized to maximize the benefits of their endosymbiotic microorganisms. In place of the usual mammalian stomach, ruminants have a large, four-chambered organ (Figure 50.17). The first two chambers, the rumen and the reticulum, are packed with anaerobic microorganisms that break down cellulose by fermentation. The ruminant periodically regurgitates the contents of the rumen (the cud) into the mouth for rechewing. When the more thoroughly ground-up vegetable fibers are swallowed again, they present more surface area to the microorganisms for their digestive actions.

The microorganisms in the rumen and reticulum metabolize cellulose and other nutrients to simple fatty acids, which become nutrients for their host. In addition, the microorganisms themselves provide an important source of protein for the host. A cow can derive more than 100 grams of protein per day from digestion of its endosymbiotic microorganisms.

50.17 A Ruminant's Stomach Bison, like their relatives domestic cattle, have a specialized stomach with four compartments that enables them to digest and obtain energy from protein-poor plant material.

Esophagus

Esophagus

Large Intestine Ruminant

The abomasum is the

"true" stomach, secreting HCl and proteases. The microorganisms are killed by the HCl, digested by the proteases, and passed on to the small intestine for further digestion.

The abomasum is the

"true" stomach, secreting HCl and proteases. The microorganisms are killed by the HCl, digested by the proteases, and passed on to the small intestine for further digestion.

The food leaving the rumen carries with it enormous numbers of cellulose-fermenting microorganisms. This mixture passes through the omasum, where it is concentrated by water absorption. It then enters the true stomach, the abomasum, which secretes hydrochloric acid and proteases. The microorganisms are killed by the acid, digested by the proteases, and passed on to the small intestine for further digestion and absorption. The rate of multiplication of microorganisms in the rumen is great enough to offset their loss, so a well-balanced, mutually beneficial relationship is maintained.

Some mammalian herbivores other than ruminants have microbial fermentation chambers in a branch off the large intestine, called the cecum. Rabbits and hares are good examples (see Figure 50.8). Since the cecum empties into the large intestine, the absorption of the nutrients produced by the microorganisms is inefficient and incomplete. Therefore, some of these animals re-ingest some of their own feces, a behavior known as coprophagy. Coprophagous species usually produce two kinds of feces, one consisting of pure waste (which they discard), and one consisting mostly of cecal material, which they reingest directly from the anus. As this cecal material passes through the stomach and small intestine, the nutrients it contains are digested and absorbed. In humans, the cecum has become the vestigial appendix, which serves no digestive function.

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Responses

  • Andrea
    What adaptations do herbivores have for a celluloseheavy diet?
    5 years ago
  • cordelia mancini
    What adaptations do herbivores have to digest cellulose?
    5 years ago
  • mario
    How long is the small intestine of ruminant animal?
    5 years ago
  • Daniel
    Why is an earthworm a herbivore?
    5 years ago
  • haddas
    What anables herbivores to diggest cellulose?
    5 years ago
  • VERA
    Why herbivores have longerintestines?
    4 years ago
  • ROMAN MACLEAN
    Have have animals adapted to cellulose digestion?
    4 years ago
  • Efrem
    What adaptations herbivores possess to digest cellulose?
    4 years ago
  • estella
    Why don't domestic herbivores make enzymes to digest cellulose?
    3 years ago
  • anja ackerman
    What special adaptations do pigs have for digesting plants?
    2 years ago
  • Robert
    What adaptation do herbivores have that enables them to digest cellulose?
    2 years ago
  • shirley
    What are the adaptations of omasum for cellulose ?
    1 year ago
  • mathilda
    What are the adaptations of herbivores which enable then to digest cellulose?
    1 year ago
  • Aatifa
    What adaptations fo rodents have to digest cellulose?
    1 year ago
  • dennis
    What are the adaptations of herbivorous which enable the to digest cellulose?
    11 months ago
  • gloriana
    What are the two adaption of herbivores?
    10 months ago
  • vittorio
    Which special adaptation of this animal to digest cellulose is unique?
    8 months ago
  • valentino milano
    HOW ARE HERBIVORES ADAPTED TO DIGESTION OF VEGETATION KCSE?
    5 months ago
  • amethyst
    What is the adaptation method that allows ruminants to digest cellulose?
    4 months ago
  • RUDIBERT
    How digestive system of herbivore is adapted to digest cellulose?
    4 months ago
  • monika
    Which enzyme enable animals to digest cellulose?
    1 month ago
  • Kenneth
    Which special organ herbivore have to digest grass?
    15 days ago

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