Avian Digestive System

• Most birds obtain food by using their beak.
• Food picked up by the beak enters the mouth.
• The mouth contains glands that secrete saliva; wets the food to make it easier to swallow and contains enzymes that start the digestion process.
• Avians use their tongue to push the food to the back of the mouth to be swallowed.
• The part between the mouth and esophagus that helps the bird swallow the food item is the pharynx.
• A flexible tube that connects the mouth with the rest of the digestive tract is the esophagus.
• The esophagus carries the food from the mouth to the crop.
• The crop is a large dilation of the esophagus that provides the capacity to hold food for some time before further digestion.
• The proventriculus, also called glandular stomach, stores and commences digestion of food before it progresses to the gizzard.
• The gizzard is a muscular stomach located immediately after the proventriculus.
• The small intestine is a relatively long tube from the exit of the gizzard to the junction of the small intestines, caeca, and the colon.
• The duodenum is the first part of the small intestine that aids in the further digestion of food coming from the stomach.
• The large intestine runs nearly a straight line below the vertebrae and ends at the cloaca.
• The main function of the caeca is the microbial fermentation of vegetable-based materials that the bird was unable to enzymatically digest.
• The cloaca is a tubular cavity opening to the exterior body and is common to the digestive and urogenital tract.
• The liver is a bi-lobed organ that lies ventrally and posterior to the heart.
• The pancreas releases glucagon, insulin, somatostatin, and avian pancreatic polypeptide, which play a role in regulating appetite, digestion, and metabolic processes.
• The appearance of an overgrown tip of the upper beak, lower beak, or both indicates beak overgrowth.
• The surface of the beak appearing brittle and crumbly instead of smooth and hard suggests bacterial and mycotic infection.
• Inability to eat and manipulate food or toys along with painful beak indicates trauma.
• Nasal discharge, sneezing, and periorbital swelling are clinical signs of Vitamin A Deficiency (Hypovitaminosis A)
• Some hens missing feathers and poultry eggshells being thin or rough are clinical signs of Calcium deficiency.