Introduction

• Cause: rapid gas production in the abomasum due to excessive fermentation of simple carbohydrates with over-growth of gas-producing bacteria.
• Signs: abomasal distension with signs of circulatory compromise.
• Diagnosis: based on clinical signs which include abomasal distension in pre-weaning calves.
• Treatment: relieve gas to reduce abomasal pressure, antibiosis to control proliferation of gas-producing bacteria, intravenous therapy as required.
• Prognosis: guarded, highly dependent on speed of recognition and treatment.

Pathogenesis

Etiology

• Some but not all cases have a confirmed bacterial involvement. Commonly:
  • Clostridia species - most frequently C. perfringens type A. Clostridial spp
  • Sarcina ventriculi.
  • Lactobacillus spp.
  • Campylobacter spp Campylobacter spp. 

Predisposing factors

General

• Decreased abomasal emptying associated with:
  • Large volume feeds.
  • High calorie feeds.
  • High osmolality feeds.
  • High glucose or electrolyte content.
• Highly fermentable, high energy feed such as milk replacer containing high levels of milk solids Feeding milk and milk replacers to calves. 
• High load of C. perfringens Clostridium perfringens type C in environment, milk replacer or feeding equipment.
• An association with sub-clinical copper Copper: overview and selenium Selenium and vitamin E: overview deficiency has been reported.

Specific

• Calves fed artificial milk replacer, particularly if:
  • Large volumes.
  • Irregular times.
  • Milk is warmer than normal body temperature.

Pathophysiology

• Reduced abomasal emptying - due to high osmolality, high volume or high glucose content of feed.
• Presence of gas-producing bacteria which then proliferate (C. perfringens type A, S. ventriculi or Lactobacillus species).
• Excessive fermentation in abomasum.
• Gas released by bacteria causes abomasal bloat.
• Distended abomasum causes compression of major blood vessels and reduces venous return, leads to circulatory shock.

Timecourse

• Abdominal distension can occur rapidly within 1 hour of feeding.
• Death can occur within minutes of severe distension or within 6-48 hours depending on the degree of circulatory compromise.

Epidemiology

• Usually sporadic but can occur as an outbreak; considered endemic on some farms.

Diagnosis

Treatment

Prevention

Outcomes