Effects of 3-methylindole in cattle

Area of Science:

• Veterinary Medicine
• Toxicology
• Animal Physiology

Background:

• 3-methylindole (3-MI) is a potential causative agent of 'fog fever' in cattle.
• Fog fever is an acute respiratory distress syndrome in cattle.
• Understanding 3-MI's role requires investigating its physiological effects.

Purpose of the Study:

• To investigate the reaction of calves to rapid intravenous injection of 3-methylindole (3-MI).
• To assess the potential role of 3-MI in the pathogenesis of 'fog fever'.

Main Methods:

• Intravenous administration of 3-MI to calves.
• Observation of physiological responses and signs of distress.
• Administration of anaphylaxis antagonists to assess mediator involvement.
• Pharmacokinetic analysis of 3-MI plasma half-life.

Main Results:

• Rapid intravenous 3-MI injection induced an anaphylactoid-like reaction in calves.
• Reduced response to repeat 3-MI doses and effects of antagonists supported this.
• The plasma half-life of 3-MI was determined to be short (14.4 minutes).

Conclusions:

• 3-MI elicits an anaphylactoid-like response in calves.
• Significant ruminal 3-MI production from L-tryptophan is required for it to cause 'fog fever'.