The digestive system of the fowl is simple but well-organized. Food is picked up by the beak and selected on the basis of feel and appearance rather than tastes. However, birds do have a functional olfactory system and the influence of taste and smell cannot be entirely overlooked.
To understand the principles behind the feeding of the chicken it is useful to look at the way the birds digest its food.
Poultry are monogastric they are unable to manufacture essential amino acids or the B vitamins, and they cannot exist on high fibre diets.
The diets of birds which are intensively housed and which have access to neither soil, grass, nor sunshine must contain the materials essential for the processes of maintenance, production, and reproduction.
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Digestive System of Poultry
The fowl is a simple stomach animal. Digestion starts from the mouth. The beak is adapted for picking of the feed. The tongue is an arrow shaped barbed like structure which forces feed into the oesophagus.
Salivary glands secrete saliva which lubricate the feed and facilitate the downward movement into the crop. The crop act as a storage pouch which retain feed for gradual passage into the stomach (proventriculus).
The feed acted upon by enzymes and amylase which break down carbohydrate. In the stomach, feed mixed with gastric juice containing enzyme pepsin and hydrochloric acid. The Pepsin breakdown protein into amino acid.
The feed particles then moves into the gizzard which is a bean shaped strong muscular organ, which crushes or breakdown feed particles by its rhythmic contraction into pulp.
This process is assisted by the presence of insoluble grit, the feed then passes into the duodenum loop which is the first part of the small intestine where most of the enzymatic digestions of feed take place. The pan crease secret various amylotic, proteolitic, and lipolitic enzyme into the duodenum.
The liver also produces bile which hydrolyses fats. Digestion is completed in the small intestine and the nutrients are absorbed through its wall. At the junction of the large and small intestine are two blind sacks known as caeca. Their main function is for fibre digestion and water absorption.
The Large intestine is also responsible for water absorption and storage of feacal matter or digesta which passes into the cloaca where they are secreted.