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Tryptamine alkaloid toxicosis in feedlot sheep
I J Lean1, M Anderson, M G Kerfoot
1Veterinary Medicine Teaching and Research Center, University of California, Davis 18830.
Journal of the American Veterinary Medical Association
|September 15, 1989
Summary
Tryptamine alkaloid toxicosis, or Phalaris staggers, caused neurological signs and death in feedlot sheep. Affected lambs showed gait issues and tremors, with brain lesions found in 60% of cases.
Area of Science:
- Veterinary Medicine
- Toxicology
- Animal Science
Background:
- Tryptamine alkaloid toxicosis, commonly known as Phalaris staggers, is a significant concern in livestock.
- Clinical signs include neurological deficits that can be exacerbated by external stimuli.
Purpose of the Study:
- To diagnose and characterize tryptamine alkaloid toxicosis in feedlot sheep.
- To identify the prevalence of associated brain lesions and potential contributing factors in feed.
Main Methods:
- Clinical examination of affected sheep.
- Gross and histopathological examination of brain tissues.
- Analysis of feed for tryptamine alkaloid and cobalt concentrations.
Main Results:
- Clinical signs observed: gait abnormalities, tremors, nystagmus, convulsions.
- Gross brain lesions (focal gray-green discoloration) and intraneuronal pigment accumulation were noted.
- 60% of slaughtered lambs had lesions consistent with toxicosis; low tryptamine alkaloid levels were detected in feed.
- Higher cobalt concentration in feed than previously associated with Phalaris staggers.
Conclusions:
- Tryptamine alkaloid toxicosis was confirmed as the cause of illness and death in feedlot sheep.
- Intraneuronal pigment accumulation in the brain stem and thalamus are key pathological findings.
- Elevated cobalt levels in feed may play a role in the pathogenesis of Phalaris staggers in sheep.