Digestive System & Associated Diseases

Digestive System Overview

• The digestive system consists of several compartments, primarily in ruminants such as cows, which digest food differently than monogastric animals.

Rumen (Paunch)

• Function: First stomach chamber that processes fibrous food.
• Connection: Entered via the esophagus; connected to reticulum through a large opening.
• Contents: Contains salivary fluids (sodium bicarbonate), water, fibers, and a complex community of microbes.
• Role of Microbes: Microbes break down cellulose and synthesize proteins and certain vitamins, enabling the animal to extract nutrients from pasture.
• Process of Rumination: Chewing the cud to aid in digestion.

Ruminal Acidosis

• Definition: A condition resulting from excessive feeding of rapidly fermentable carbohydrates without sufficient fiber.
• Symptoms: Low ruminal pH, reduced feed intake, and subsequent health problems, which counteract any weight gains from high grain diets.

Reticulum

• Structure: Second stomach chamber with a honeycomb-like lining.
• Function: Screens out large items and allows smaller feed particles to pass to the omasum, aiding in digestion.
• Flushing Action: Facilitates separation of small and large particles.

Bovine Traumatic Reticulopericarditis (Hardware Disease)

• Cause: Occurs when metallic objects ingested by cows penetrate the reticulum, leading to severe complications.

Omasum

• Structure: Third stomach chamber shaped like a sphere, connected to the reticulum by a short tunnel.
• Function: Absorbs volatile fatty acids and approximately 60-70% of water, aiding in nutrient absorption.

Abomasum

• Description: The true stomach, similar to the glandular part of a monogastric stomach.
• pH Level: Ranges from 3.5 to 4.0.
• Enzymatic Activity: Uses enzymes to break down proteins, adding moisture to the food mixture.

Abomasal Impaction

• Cause: Linked to excessive consumption of roughage that is low in digestible protein and energy.
• Symptoms: Dehydration, lack of appetite (anorexia), scant feces, abdominal distension, weight loss, and overall weakness.

Intestines

• Small Intestine: Comprises duodenum, jejunum, and ileum, lined with mucous membranes and muscle layers for involuntary movement.
• Large Intestine: Comprises cecum, colon, and rectum, serving a role in water absorption and waste formation.

Transmissible Gastroenteritis (TGE)

• Cause: Viral disease caused by a coronavirus affecting pigs (small intestine).
• Symptoms: Vomiting and severe diarrhea leading to dehydration due to destruction of jejunal and ileal epithelial cells.

Enterotoxemia

• Pathogen: Caused by Clostridium perfringens, a rod-shaped Gram-positive bacterium.
• Symptoms: Production of toxins (epsilon) that lead to necrosis of intestines, hemorrhaging, and possibly perforation, affecting animals like goats, sheep, and cattle.

Bovine Viral Diarrhea (BVD)

• Symptoms: Present biphasic fever (up to 40°C), depression, reduced milk production, inappetence, rapid respiration, and excessive nasal and eye secretions, culminating in diarrhea.
• Classification: BVDV belongs to the Pestivirus genus in the Flaviviridae family.

Potomac Horse Fever

• Pathogen: Caused by Neorickettsia risticii, a Gram-negative bacterium.
• Mechanism: Infects enterocytes in both small and large intestines, causing acute colitis.
• Transmission: Inadvertently ingested aquatic insects acting as vectors may introduce the bacterium into the horse's system.