The use of cannabidiol as a novel treatment for crib-biting or cribbing in a horse

Behaviour is the response of living things to their environment and external stimulation, and is one of the parameters to be observed when assessing animal welfare. Any alteration from the conditions found in nature can lead to the occurrence of some specific behaviours, called stereotypies which are characterised as repetitive, consistent patterns of behaviour usually defined as having no apparent ultimate or proximal functions.

It has been reported that once stabled or subjected to stressful activities, horses have more susceptibility of developing behavioural disturbances; therefore, behavioural disorders in horses are a strong indicator of poor welfare. Cannabis spp.-derived molecules have been studied under different medical conditions; the therapeutic potentials of phytocannabinoids are related to the effects of delta-9-tetrahydrocannabinol, cannabidiol (CBD), and other compounds.

Cannabidiol has many activities within the central nervous system, such as anxiolytic, antidepressant, antipsychotic, anticonvulsant, and anti-inflammatory activities. Some studies have recently shown the potential and successful therapeutic use of phytocannabinoids in veterinary medicine. This clinical case report described a 22-year-old mare suffering from chronic crib-biting and wind-sucking, and the successful outcome of four weeks-therapy with CBD. This is the first report of the successful therapeutic use of phytocannabinoids in equine behavioural disorders.

Introduction

Behaviour is the response of living things to their environment and external stimulation, and is one of the parameters to be observed when assessing animal welfare. Any alteration from the conditions found in nature can lead to the occurrence of some specific behaviours, called stereotypies (ezfouli et al., 2013; Mason, 2006) which are characterised as repetitive, relatively consistent patterns of behaviour, usually defined as having no apparent ultimate or proximal functions.

Stereotypies also exist in humans; they can be either psychologically or environmentally induced, and are often associated with developmental disorders, such as autism, neurological disorders, obsessive-compulsive disorder (OCD), Tourette's syndrome, and severe psychiatric disturbances (McBride and Hemmings, 2005).

It has been reported that once stabled or subjected to stressful activities, horses are more susceptible to development of behavioural disturbances, therefore, behavioural disorders in horses are a strong indicator of poor welfare (Lesimple, 2020). The most common behavioural disorders in horses are crib-biting and wind-sucking, weaving and box walking; in Europe and Canada, the prevalence of crib-biting and wind-sucking is 2.4% and 8.4%, respectively (Wickens and Heleski, 2010).

Horse owners and veterinarians are often concerned about the stereotypic activities resulting in a reduction in performance, decreased monetary value of the animal, and the development of secondary pathologies, such as gastric ulcers and colic syndrome (Buitrago et al., 2022).

The neurobiological bases of sensitisation may represent a common substrate for different mental and biological disturbances across species (e.g., mouse stereotypies, schizophrenia, and addiction in humans) (Kelly et al., 2021). Primary studies carried out in the 20th century have already shown the role of the basal ganglia in the development of abnormal behaviours (Karler et al., 1997; Smelik and Ernst, 1966).

An in-depth investigation by McBride and Hemmings (2009) showed receptor-based alterations in the basal ganglia in crib-biting horses. Behavioural frustration and the expression of equine stereotypy are linked with dopamine receptors, i.e., the DRD4 (dopamine D4 receptor subtype) gene (McBride and Hemmings, 2005; Ninomiya et al., 2013).

The expression of cannabinoid receptors types 1 (CBR1) and type 2 (CBR2) and the cannabinoid-related receptors transient receptor potential vanilloid type 1 (TRPV1) and G protein-receptor 55 (GPR55) has been shown in rat and human basal ganglia (Chayasirisobhon, 2019). Chiocchetti et al. (2021a, 2021b) successfully demonstrated the expression of cannabinoid and cannabinoid-related receptors in the dorsal root ganglia and enteric nervous system of horses.

Receptors and their ligands are compounds of the endocannabinoid system (ECS) which has evolutionarily been conserved and has been characterised within all vertebrates and many non-vertebrate species (Elphick, 2012). It is currently known that cannabinoid and cannabinoid-related receptors are present in the central and peripheral nervous systems and in peripheral tissues where their balanced expression regulates tissue homoeostasis (Joshi and Onaivi, 2019).

Cannabis spp.-derived molecules (phytocannabinoids) have been studied under different medical conditions; the therapeutic potentials of phytocannabinoids are related to the effects of delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), and other Cannabis spp. compounds, such as cannabigerol, cannabichromen, etc.

Cannabidiol has shown to have benefits in a variety of disorders, such as: autism spectrum disorder, anxiety, psychosis, neuropathic pain, cancer pain, human immunodeficiency virus, migraine, multiple sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, hypoxic-ischemic injury, and epilepsy (Morris et al., 2021; Van der Stelt and Di Marzo, 2003).

Some studies have recently shown the potential and successful therapeutic use of phytocannabinoids in veterinary medicine, using CBD as the molecule of choice to treat mechanical allodynia, lower horses reactivity, and improve joint pain (Ellis and Contino, 2021; Sánchez-Aparicio et al., 2020).

Traditional therapies such as cervical collars, environmental enhancement, dietary modification, chemical anxiolytics (e.g. acepromazine) and surgery may not be successful in a significant percentage of cases, therefore new therapies are needed (Houpt and McDonnell, 1993; Nagy and Bodó, 2009).

This case report described the clinical findings of a mare diagnosed with chronic crib-biting and wind-sucking, and the successful management and treatment with isolated CBD. To the Authors’ knowledge, this is the first report of the successful therapeutic use of phytocannabinoids in equine behavioural disorders.

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Source: https://www.sciencedirect.com/science/article/pii/S2451943X23000066?via%3Dihub