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Operant analysis of chronic locoweed intoxication in sheep
J A Pfister1, B L Stegelmeier, C D Cheney
1Poisonous Plant Research Laboratory, ARS, USDA, Logan UT 84341, USA.
Journal of Animal Science
|November 1, 1996
Summary
Intermittent locoweed (Oxytropis sericea) ingestion in sheep caused persistent behavioral changes, even after toxic effects resolved. Cyclic grazing requires caution, as 4 weeks of exposure may lead to long-term operant response abnormalities.
Area of Science:
- Veterinary Toxicology
- Animal Behavior
- Rangeland Management
Background:
- Locoweed (Oxytropis sericea) poisoning is a concern in livestock.
- Understanding the behavioral impacts of intermittent toxin exposure is crucial for animal health and agricultural practices.
Purpose of the Study:
- To investigate the effects of intermittent locoweed ingestion on operant responding in sheep.
- To determine the duration of behavioral abnormalities following locoweed exposure.
Main Methods:
- Sheep were fed locoweed or alfalfa pellets, and their operant response rates (fixed ratio and fixed interval) were monitored.
- Histological examination was performed to assess neurovisceral vacuolation.
Main Results:
- Locoweed-treated sheep showed decreased fixed ratio response rates and altered response patterns, including longer post-reinforcement pauses.
- Behavioral abnormalities persisted for over 6 weeks, despite rapid resolution of histological signs of intoxication in some animals.
- Overt intoxication signs and neurovisceral vacuolation were observed in stressed sheep after 17 weeks.
Conclusions:
- Intermittent locoweed grazing requires caution due to potential persistent behavioral abnormalities.
- An initial 4-week exposure period may be excessive, leading to prolonged deficits in operant responding.
- While histological pathology may resolve quickly, behavioral recovery can take significantly longer.