Digestive System and Associated Diseases Notes

Types of Digestive Systems

• Monogastric System:

  • Has a single stomach.

  • Examples: Humans, pigs, dogs, cats, fish.

  • Digestion includes mechanical breakdown and chemical digestion (stomach secretes acid with pH of 1.5 to 2.5).

  • Better suited for diets high in concentrates (cereal grains, oil meals).

  • Salivary glands (Parotid, Mandibular, Sublingual) aid in lubrication and food breakdown.

• Avian System:

  • Found in birds (poultry).

  • Lacks teeth; food is broken down using pecking and scratching.

  • Digestive components include:

  • Crop: Food storage and soaking.

  • Proventriculus: Glandular stomach (secretes pepsinogen and hydrochloric acid).

  • Gizzard: Muscular organ; grinds food, often contains grit or stones.

  • Cloaca: Common outlet for waste.

• Ruminant System:

  • Contains a four-compartment stomach (Rumen, Reticulum, Omasum, Abomasum).

  • Examples: Cattle, sheep, goats.

  • Specialized for digesting high-fiber feed (roughages like hay and silage).

  • Food is swallowed, then returned to the mouth as cud for re-chewing.

  • Rumen: Contains microbes for fermentation.

• Pseudo-ruminant System:

  • Similar to ruminants but lacks a multi-compartment stomach.

  • Uses the large cecum for fiber digestion.

  • Examples: Horses, rabbits, guinea pigs.

Functions of the Digestive System

• Digestion:

  • Mechanical (chewing, segmentation) increases surface area.

  • Chemical digestion involves enzymes and secretions to break down food.

• Absorption:

  • Primarily occurs in the small intestine where nutrients enter the bloodstream.

  • Lipids absorbed via lacteals (lymphatic vessels).

• Motility:

  • Propulsion moves food through the tract via peristalsis (wave-like muscle contractions).

• Elimination:

  • Waste is expelled through defecation.

Digestive Disturbances

• Symptoms indicating issues in the digestive system:

  • Loss of appetite

  • Inability to chew or swallow

  • Vomiting

  • Bloating

  • Abnormal feces

  • Excessive salivation

  • Fever

Specific Diseases

• Foot & Mouth Disease (FMD):

  • Affects cloven-hoofed animals (cattle, pigs, goats).

  • Symptoms: Oral ulcers, fever, lameness, blisters in mouth.

  • Not typically fatal but reduces production significantly.

• Vesicular Stomatitis:

  • Causes lesions and ulcers in the mouth of cattle, swine.

  • Signs include salivation and lameness.

• Edema Disease (ED):

  • Caused by E. coli toxins, primarily in weaned pigs.

  • Symptoms include edema, sudden death, and high mortality.

• Macrorhabdosis (Megabacteriosis):

  • Caused by the fungus Macrorhabdus ornithogaster affecting the avian proventriculus.

  • Symptoms include weight loss despite increased food intake.

Anatomical Structures

• Esophagus:

  • Transfers food via peristaltic movements.

  • Comprises muscular layers; functions involuntarily.

• Stomach:

  • Monogastrics: Simple stomach with acidic gastric juices.

  • Ruminants: Multi-chambered to facilitate fermentation and digest roughage.

• Salivary Glands:

  • Aid in digestion by moistening and enzymatically breaking down food.

Nutritional Implications

• Understanding digestive systems helps select appropriate feeds:

  • Concentrates: Highly digestible and energy-rich feeds for monogastrics.

  • Roughages: High-fiber feeds essential for ruminant health.

• Importance of Microorganisms:

  • Ruminants rely on diverse bacteria, protozoa, and fungi for effective digestion of fiber and nutrient synthesis.