Agriculture Reference
In-Depth Information
8
Digestive Physiology and
Nutrient Metabolism
S.G. Solaiman , PhD, PAS and F.N. Owens , PhD, PAS
KEY TERMS
Fermentation—microbial conversion of substrates into acids and gases under anaerobic (oxygen-free) conditions.
Rumination—the process of regurgitation, re-mastication, re-insalivation, and re-swallowing of feeds, specifi c to and
characteristic of ruminants.
Digestion—mechanical, chemical, and enzymatic breakdown of food nutrients within the gastrointestinal (GI) tract.
Absorption—passage of nutrients from intestinal lumen into the intestinal wall (epithelium) usually followed by
passage into the blood.
Required nutrients—nutrients needed to sustain life.
Digestive disorders—diseases resulting from dysfunction of the GI tract.
Prehension—capacity to grasp food for consumption.
Mastication—chewing food to reduce particle size.
Salivation—production of saliva that lubricates ingested foods for swallowing and assists in food digestion.
Ionophores—polyether antibiotics that modify microbial fermentation in the rumen.
OBJECTIVES
By completing this chapter, the reader will acquire knowledge on:
￿ Animal classifi cation based on feed choice
￿ Work of digestion by goats
￿ The role of microorganisms in ruminant digestion
￿ Digestion by preruminant (young) kids
￿ Ruminal dysfunction
￿ Nutrients required within a goat 's diet
INTRODUCTION
The gastrointestinal (GI) tract of domestic animals differs,
and this difference is related to their preference for and use
of dietary components. Animals are classifi ed into three
groups based on their diet type. Herbivores are animals
that have a digestive system adapted to eat and digest
fi brous plant materials; carnivores are animals with a
digestive system adapted to digest meat and meat compo-
nents; and omnivores are those with a digestive system
adapted to consume a mixture of plant and animal matter.
As a ruminant, the adult goat can consume and digest
fi brous plant materials and therefore is classifi ed as an
herbivore. Other ruminants include cattle, sheep, deer,
elk, and many other wild ruminant species. These all are
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