The effects of pelleted cannabidiol supplementation on heart rate and reaction scores in horses

Abstract

The potential use of cannabidiol (CBD) as a nutraceutical to support improved health and welfare has been of increasing interest. In particular, CBD has been shown to decrease anxiety in humans and small animals. While there is little research published on the effects of CBD supplementation in horses, its use is increasing rapidly.

The objective of this study was to determine the effect of feeding a pelleted CBD supplement on equine reactivity and heart rate (HR). Seventeen stock-type geldings were divided into control (CON) or treatment (TRT) groups. The TRT group received 100 mg of CBD once daily. Control horses were maintained on their standard diet without supplementation. A novel object test was used to evaluate changes in HR and reactivity before and after 6 weeks of supplementation. Heart rate was recorded before, at, and after exposure to the novel object.

Reactivity when the horse was exposed to the novel object was scored live and through video review. There was no difference in starting, stimulus, or final HR, but TRT horses exhibited less reactivity after 6 weeks of supplementation. Results suggest that CBD supplementation may lower reactivity in horses.

Introduction

Nutraceuticals encompass a broad range of herbal substances containing physiological benefits specifically pertaining to chronic diseases (Nasri et al., 2014). Research trials related to the use of nutraceutical products to improve health and wellness have increased (Daliu et al., 2019; Gupta et al., 2019). Cannabis sativa (hemp) contains the nutraceutical, cannabidiol (CBD).

Cannabidiol is one of more than 85 active cannabinoids found within the cannabis plant, and accounts for almost 40% of the cannabis plant's extract (National Center for Biotechnology, 2020). Naturally occurring endocannabinoids and relative receptors are part of the endocannabinoid system (National Center for Biotechnology, 2020).

Phytocannabinoids such as CBD work by activating this regulatory system and consequently influence a number of physiological and cognitive processes, including but not limited to: energy balance regulation (Cota, 2007), appetite (Wiley et al., 2009; Jamshidi and Taylor, 2009), feelings of reward or satisfaction (Gardner, 2005), endocrine and central nervous system function (Di Marzo et al., 1998), and reproduction (Park et al., 2004).

Cannabidiol should not be confused with tetrahydrocannabinol (THC), the psychoactive compound found in marijuana. In a review of studies on CBD and THC interactions, CBD has reduced the effects of THC (Freeman et al., 2019). Cannabidiol has been shown to have physiological and behavioral impacts on human recipients (Crippa et al., 2011).

It has also demonstrated involvement within the limbic system where emotions and behavior are processed (Fusar-Poli et al., 2009), and can influence endocrine function to assist in behavior reinforcement (Morgane et al., 2005).

Supplementation with CBD has been shown to reduce anxiety related responses in mice with Fragile X Syndrome (Zieba et al., 2019). This neurological disorder impacts intellectual, social, and physical development. Mice administered CBD have also shown decreased symptoms of obsessive-compulsive disorder (Deiana et al., 2012).

The alteration of neurotransmitter release from the brain by cannabinoids, could result in pain reduction and muscle relaxation, as well as antioxidant and anti-inflammatory action (Serpell et al., 2014; Atalay et al., 2020). Cannabinoid receptors have been verified in the sensory neurons and satellite glial cells of the dorsal root ganglia in the equine brain (Chiocchetti et al., 2020).

The dorsal root ganglia contain nerves that relay sensory information to the spinal cord, supporting the investigation of CBD for pain management. Additionally, an equine case study revealed alleviation of neuropathic pain within 48 hours of treatment with a twice daily 0.5 mg/kg BW dose of pure crystalline oral CBD (Ellis and Contino, 2019).

While dosage was successfully reduced to a once daily 0.33 mg/kg BW, the treatment could not be completely removed without symptom recurrence. Cannabidiol has also been used to treat epilepsy in both humans (Devinsky et al., 2017) and dogs (McGrath et al., 2019).

There are claims in lay literature that CBD supplementation affects heart rate, however, this assertion has not been supported by published research. In a research review of CBD supplementation in mice, rats, humans, and piglets, no difference in heart rate was noted compared to controls (Bergamaschi et al., 2011).

Not all effects of CBD appear to be positive. Mice administered CBD had reduced sexual behavior and fertility (Carvalho et al., 2018). Male mice supplemented with CBD showed a delay in performing the first mount and a reduced number of mounts and ejaculations.

Female mice supplemented with CBD showed a 30% reduction in fertility and a 23% reduction in the number of litters (Carvalho et al., 2018). Also, despite staying within reference ranges, alkaline phosphatase concentrations increased when osteoarthritic dogs were treated with CBD oil for 4 weeks (Gamble et al., 2018).

While there has been research on the effects of CBD supplementation in humans and small animal species, there is very little research reported in equines. Even so, horse owners are increasingly using CBD supplements on their animals. The objective of this project was to evaluate the effects of pelleted CBD supplementation on equine heart rate and behavior.

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Source: https://www.sciencedirect.com/science/article/abs/pii/S1558787821001258?via%3Dihub

The effects of pelleted cannabidiol supplementation on heart rate and reaction scores in horses