Animal Digestive Systems Topic # 3024 Ms. Blakeley

Digestive System – Objectives n Describe and understand the basic functions of the primary components of the digestive system. n Compare the functions and locations of the digestive organs in man, poultry, horses, cows and swine. n Differentiate between and identify digestive systems of man, horses, swine, poultry and cows.

Digestive System n Where large complex molecules are broken down into simpler molecules n Digestive Tract: –Long tube beginning with mouth and ending with the anus n Polygastric (Ruminant) –A stomach with more than one compartment (cows, sheep, deer) n Monogastric (Non-ruminant) –A stomach with one compartment (swine, horses) n Avian (Poultry) –No true stomach (chickens, geese)

Digestive Systems n Man & Pig have a simple stomach with an extensive intestinal system n Horses & Rabbits have a simple stomach with an extensive intestinal system and an enlarged caecum n Ruminants have a complex stomach with a simpler intestinal system n Poultry have no teeth and no true stomach with a crop and gizzard to grind food

Mouth & Esophagus n Mouth: “prehensile” tool (grasps & mixes food) –Chewing breaks down food –Salivary Glands secrete juices containing enzymes (digest food) –Mucin lubricates the feed for swallowing n Esophagus: muscular tube that connects mouth to stomach –Peristaltic waves send feed down the esophagus, (muscle contractions). –Reverse Peristalsis = blowing chunks –The cardia, located at the end of the esophagus prevents feed in the stomach from coming back into the esophagus. ( non-ruminants only)

Simple Stomach n Muscular organ, receives feed n Gastric juices are secreted by the glands in the stomach wall –start when masticated feed enters the stomach –Gastric juices have about 0.2 to 0.5 percent HCl n The wall of the stomach is lined with muscle, this muscle churns and squeezes the feed –This action forces the liquid portion on into the small intestine

Ruminant Stomach n Occupies 3/4 of abdominal cavity, mostly on the left side n Rumen (paunch): 80% of stomach, lighter food collects here –Microbes digest cellulose –Uses lots of water n Reticulum (hardware stomach): 5% of stomach, heavy foreign items are trapped here

Ruminant Stomach (cont.) n Omasum (many plies): 8% of stomach, absorbs water n Abomasum (true stomach): 7% of stomach, typical enzyme activity n Rumination= regurgitation, re-chewing of food

Rumination (regurgitation) n After rumen if full, it lies down to ruminate (chew its cud) n Cattle spend from 5-7 hours ruminating, broken up into 6-8 periods n Regurgitation is the process of forcing the feed back into the mouth for chewing n Done through a series of muscular contractions and pressure in the rumen and reticulum

Avian stomach/gizzard n Since chickens have no teeth, they swallow food whole and it’s stored in the crop n Feed in proventriculus are secreted by the glandular stomach and mixed with feed n The feed moves to the gizzard and is ground n Epithelium breaks the feed into smaller particles, further mixing proventricular digestie juices with the feed in the gizzard n The end of the digestive system is the vent

Small & Large Intestines n Small Intestine: long coiled tube connecting stomach to large intestine –rest of the digestion and absorption takes place here –surface covered with villi (surface area) n Large Intestine: Caecum, colon, rectum –absorbs water (makes feces more solid) –some vitamins & minerals absorbed here –Cecal Fermenters (Horse): similar to rumen