VPB 121: Veterinary Physiology - II (2+1)

Digestion

DIGESTION IN BIRDS

Enzymatic digestion

• After ingestion, the food is mixed with saliva and mucous to moisten the food.  Amylase, is produced by the salivary and oesophageal glands.
• The secretions of the proventriculus or glandular stomach are hydrochloric acid, pepsin that acts on protein and the hormone gastrin that stimulates the production and release of gastric juice in the proventriculus and pancreatic juice from the pancreas.
• Gizzard is a very powerful muscular organ actively involved in  breaking the food particles into smaller sizes. The enzymes released into the food with the saliva and by the proventriculus are also thoroughly mixed with the food. This breaking and mixing function of the gizzard is enhanced by the presence of insoluble grit such as stones.
• Pancreatic juice and bile from the liver enters via ducts located at the distal end of the duodenum at about the junction of the duodenum and the jejunum.  The digestive process starts prior to the entry point to the small intestine due to back flow of pancreatic juice and bile towards the gizzard.
• In addition to enzymes, the pancreas produces insulin and sodium bicarbonate. Insulin is involved in the maintenance of blood sugar levels while the sodium bicarbonate, being strongly alkaline, will increase the pH of the intestinal contents.
• The small intestine also produces enzymes that play their part in the digestive process of reducing the complex food compounds into  simple building blocks that can be absorbed across the intestinal wall for the transport to the organ for further processing or storage.
• Food materials that escape enzyme action are subjected to bacterial breakdown in the caeca.