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Agriculture for Secondary Schools

Caecum containing
oesophagus Stomach bacteria to digest
cellulose
Ileum

Rectum

night faeces
Pancreas Colon
Food is eaten
for the first
time Night faeces are eaten and absorbed
the second time the food is swallowed

Figure 5.6: Digestive system of a rabbit
The monogastric herbivores have long small intestine, large caecum and fast rate of
passage of digesta. The hind gut represents about 60% of the volume of their Gastro
Intestinal Tract (GIT). Digestion begins by mechanical grinding of the feed in the
mouth where there is also a large amount of saliva secretion. The finely grinded
material is thoroughly mixed with the saliva and is swallowed via the oesophagus
into the stomach. Within the stomach, the feed is broken down into its constituents
of different nutrients. As the material passes through the duodenum to the small
intestine, it is mixed with pancreatic enzymes and digestion continues.
Digestion of fibre occurs in the hind gut, specifically in the caecum. Within the
caecum, there is a large population of bacteria and protozoa. The caecal microbes
act on the fibre in the same way as those in the rumen of ruminant animals to
produce volatile fatty acids. Some of these acids are absorbed through the lining of
the large intestine to be utilised as source of energy by the host. In rabbits, upon the
caecum fermentation, the caecal contents are compressed by caecal wall muscles to
form small wet pellets called caecotrophes. When the caecotrophes are passed out in
faeces, the rabbits identify them as nutrient rich materials and consume them again
as food. This habit is known as caecotrophy. The caecotrophes become available
again to the rabbit as they are recycled back through the entire GIT for re-digestion.

Digestive system and digestion in monogastrics
Monogastric animals have a simple stomach which is fully developed for digestion
of concentrate feeds. They have a wide choice of feeds which include both plant and
feeds of animal origin. Although they can consume fibrous materials, their ability
to utilise them is very limited. Pig is one example of monogastric animals. The

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