Pathogenesis of "Indigestion" in Poultry: Overlooked Clinical Factors Summary for Clinicians

Pathogenesis of "Indigestion" in Poultry: Overlooked Clinical Factors
Summary for Clinicians By: Dr. Satang (Sekthachon Phoemyao, DVM) & Ajan Kaew (Asst. Prof. Somphoth Weerakul, DVM, PhD)

Kwankhum Animal Hospital, Khon Kaen

Terminology: Indigestion vs. Crop Stasis
While owners frequently use the term "indigestion," clinicians should interpret this as crop delayed or crop stasis. In avian medicine (specifically psittacines), this is often secondary to primary gastrointestinal (GI) dysfunctions leading to gastroenteritis and ileus. Common differentials include PDD, PBFD (in juveniles), Polyomavirus, and various bacterial, yeast, or viral infections that trigger GI inflammation.

In gamefowl (fighting cocks), "indigestion" can signal severe systemic diseases:

Newcastle Disease: Radiographs often reveal localized ileus or focal gas accumulation. While inflammation is widespread, the gizzard typically shows the most distinct localized inflammatory changes on imaging.
Fowl Cholera: Presents with diffuse coelomic inflammation and generalized ileus, consistent with avian sepsis. These cases usually involve multi-organ systems (respiratory, cardiovascular, neurological, hepatic, and splenic).
The Role of Dietary Carbohydrates and Dysbiosis
Many cases are non-infectious in origin but present with primary GI stasis (crop delayed $>6$ hours). Patients are often presented late—days after the stasis began—resulting in severe clinical progression.

Clinical Profile:

Signalment: Growing chicks or adult gamefowl undergoing intensive training/conditioning.
Symptoms: Anorexia, rapid weight loss (BCS 1-1.5/5), abdominal pain (hunched posture, dropped head/tail/wings), depression, and ruffled feathers.
Droppings: Increased urates (white) and dark green feces (biliverdin).
Note: Birds may exhibit displacement activities (preening or pecking at food) despite severe illness.
Pathophysiology of "Sour Crop" and Lactic Acidosis:

High-value gamefowl are often overfed with high-energy diets (cooked rice, dairy cow feed, sow feed, or high-protein supplements with high starch content).

Fermentation: Excessive starch leads to overgrowth of starch-utilizing bacteria.
Lactic Acid Production: High concentrations of lactic acid accumulate, primarily in the ileum, followed by the crop, gizzard, and cecum.
Mucosal Damage: Excess acidity triggers histamine release and hypersecretion of mucus (as a buffer), damaging the GI lining.
Dysbiosis: The acidic environment inhibits beneficial microflora, lowering local immunity and allowing opportunistic pathogens (Gram-negative bacteria like E. coli, Salmonella, Pasteurella, Mycoplasma; and yeast like Candida albicans) to proliferate. This results in sour crop and significant small intestinal gas distension (ileus) visible on X-ray.
Clinical Management Principles
Effective treatment must address the underlying cause while stabilizing the patient:

Nutritional Correction: Adjust the diet during recovery to prevent further fermentation.
Microbial Balance: Utilize specific probiotics that utilize lactic acid and convert it into volatile fatty acids (VFAs) to restore pH balance.
Pain Management: Address severe visceral pain and inflammation.
Antimicrobial Therapy: Since opportunistic pathogens are typically Gram-negative, a combination antibiotic therapy targeting Gram-negatives is often more effective than a single broad-spectrum agent in cases of generalized ileus.
Supportive Care: Aggressive fluid therapy (tailored to the degree of dehydration) and specialized recovery diets are essential for moderate to severe cases.