Investigation into the use of narcotic antagonists in the treatment of a stereotypic behavior pattern (crib-biting) in the horse.

The research article investigates the potential of narcotic antagonists in treating a behavior pattern in horses known as crib-biting, and suggests that using these drugs can effectively suppress this behavior for extended periods.

Understanding Crib-biting and its Implications

• Crib-biting is a compulsive, repetitive behavior in horses, where they bite on objects, often stalls or fences, with the neck stretched and air sucked in. This can cause dental problems, damage to stables, and potential digestive issues in horses.
• The researchers suggest that this behavior may involve the activation of narcotic and dopamine receptors in the horse’s central nervous system (CNS).

The Research Methodology

• The researchers studied the frequency of crib-biting in seven untreated horses under controlled conditions and found the frequency ranged from 0.3 to 14.9 bites per minute.
• Various narcotic antagonists were administered to these horses in different doses, either intravenously or intramuscularly, to study their effects on the crib-biting behaviour.
• The responses to narcotic antagonists were measured in terms of reduction in crib-biting rates and duration of the response.

The Findings

• The study found that narcotic antagonists significantly decreased the crib-biting rates. The behavior rate dropped to almost zero within about 20 minutes after administration of the drug.
• The duration of the drug’s effect varied, with a single dose of naloxone lasting approximately 20 minutes, while nalmefene and diprenorphine’s effects could last 4 hours or more.
• Continuous infusion of nalmefene could completely prevent crib-biting for up to a week. However, once the infusion was stopped, and nalmefene levels in the plasma dropped below 5 ng/ml, crib-biting behavior resumed.
• Large doses of nalmefene caused minor side effects such as semi-fluid fecal matter, mild sedation and intermittent penile relaxation. However, these side-effects were not debilitating; horses were still responsive to stimuli, maintained their appetites, and performed appropriately when ridden. Sedative effects also wore off during the course of prolonged infusions.

Implications and Future Directions

• The findings suggest that narcotic antagonists could potentially be used as an effective treatment strategy for crib-biting, a stereotypic behavior disorder in horses.
• However, it’s important to note that crib-biting behavior resumes once the drug concentrations drop, meaning it could likely be only a temporary solution and not a complete cure.
• The side effects, while minor, should be considered and further research is potentially needed to study long-term impacts of these narcotic antagonists on horses.
• This novel treatment strategy opens up avenues for further investigations into the use of similar strategies for other stereotypic behavior disorders in animals.