Large Animal

Cannabidiol (CBD) is one of the major non-psychoactive cannabinoids produced by Cannabis sativa L. Hemp is classified as a Cannabis varietal because it has less than 0.3% tetrahydrocannabinol (THC) – the psychoactive component found in Cannabis. Recent studies have shown that CBD has good tolerability and a wide range of reported health benefits. The purpose of this study was to measure the effects of CBD increase movement and promote calmness in horses. CBD was studied in horses after the administration of two oral doses (50 mg each) each day over a two-week timeframe. Fortyone horses were studied across the United States and participants were obtained through relationships with horse shelters, rescues, farms with retired show and race horses, and general pleasure horse farms. In all of the cases, the horses were evaluated and determined, at the outset, to have impaired movement & presentation and/or demonstrated common vices of anxiety like cribbing, pacing or reluctance to load to trailers or gates.

Cannabis sativa L. contains cannabidiol (CBD), a compound that has many anti-inflammatory properties. In this study, 99.9% CBD powder was used to determine its in vitro efficacy as an anti-inflammatory agent. Heparinized blood was collected via jugular venipuncture from senior horses. PBMCs were isolated then incubated for 24 hours with increasing dilutions of CBD dissolved in DMSO. PBMCs were stimulated the last 4 hours of incubation with PMA/IO and Brefeldin A. A Vicell counter was used to evaluate viability after incubation. PBMCs were stained intracellularly for IFNγ and TNFα then analyzed via flow cytometry. RT-PCR was used to analyze samples for gene expression. Five equine-specific intron-spanning primers/probes used are: CB1, CB2, TNFα, IFNγ, IL-10, and Beta-glucuronidase. Data was analyzed using RM One-way ANOVA (significance P < .05). Viability of PBMCs with CBD was completed to determine cytotoxicity. The dilution of CBD that did not affect cell viability was 4 µg/mL (P<0.05). CBD at 4 µg/mL significantly reduced production of IFN-γ and TNF-α (P < .05). RT-PCR results for TNFα and IFNγ at 4 µg/mL showed a reduction compared with the positive control and IL-10 showed a similar reduction at 2 µg/mL and 4 µg/mL. RT-PCR gene expression results showed significance for 10 μg/mL CBD in CB1 and CB2. CBD at 4 µg/mL reduced in vitro production of inflammatory cytokines from senior horses. This in vitro study supports further investigation of CBD to determine if it may be effective as an anti-inflammatory treatment for chronic inflammation in the horse.

A multitude of claims exist regarding therapeutic benefits of cannabidiol (CBD) in human and animal medicine. Though supportive evidence of CBD as a nutraceutical option exists, lack of regulation means that product safety, consistency, and efficacy cannot be guaranteed. Trials for specific conditions and species are needed. The objective of this study was to evaluate CBD safety and use effects on reactivity and movement in the horse. Project 1 examined the bioavailability of a single 50 mg dose of an oil and pelleted CBD product. One of 2 Quarter Horse geldings received the oil product. The second received the pelleted product. Blood samples for serum cannabinoid concentration occurred at 1 h and 2 h post administration. Both products were below LLOQ at 1 h and detectable at 2 h post administration (PEL= 0.163 ng/ml; OIL 0.11 ng/ml). Project 2 examined pharmacokinetics of a single feeding of pelleted CBD at 50 mg (TXT1), 100 mg (TXT2) and 250 mg (TXT3) in 18 stock-type geldings. Blood was collected at 0 (pretreatment), 0.5, 1, 2, 4, and 12 h post treatment for serum CBD concentration. Safety was monitored via serum chemistry and complete blood count. Statistical analysis was completed on serum chemistry values through the PROC MIXED procedure of SAS. Though CBC and serum chemistry results were within reference ranges, treatment differences were observed for creatinine (TXT1=1.41, TXT2=1.22, TXT3=1.49; P ≤0.01) and blood urea nitrogen (BUN; TXT1=15.5, TXT2=16.52, TXT3=18.61; P≤0.03). Peak serum CBD concentrations were observed at 2 h post TXT. The results demonstrated relative safety of a single CBD dose up to 250 mg in the horse, providing foundational knowledge concerning equine dosing. Project 3 evaluated pelleted CBD fed once daily over 6 wk to 24 university riding horses. Pre- and post-TXT evaluations were completed vi on movement parameters and reactivity. Movement analysis examined stride length, and duration of stance and swing phase. Reactivity was observed through a novel object test (NOT). Reactivity scores were documented via live and video evaluators. Heart rate (HR) monitors collected HR data at NOT test points: start, stimulus, and stop. Instructors completed surveys to evaluate movement and behavior patterns of horses during classes. The population was reduced to stock-type geldings (n=17) for NOT and movement statistical analysis. The population was further reduced (n=15) for survey data to only evaluate stock type geldings observed in duplicate (before and after supplementation). Main effects included heart rate (HR), time on stride length (SL), and duration of stance or swing phase. Data was analyzed using the PROC MIXED procedure of SAS and survey data were evaluated using Chi Square for the effect of TXT and age on reactivity scores from the novel object test (NOT). Fisher’s Exact Test was implemented if fewer than 5 responses were observed per observation parameter. No differences were observed in NOT HR values. Low reactivity scores were more frequently observed in TXT horses after 6 wk. During walk, TXT horses spent more time in stance phase (TXT=0.57 sec, CON=0.51 sec; P<0.01) and swing phase (TXT=0.38 sec, CON=0.36 sec; P<0.01). In both groups, walk stance phase duration increased over time (Pre=0.37 sec, Post=0.71 sec; P<0.01), while duration of trot stance (Pre=0.30 sec, Post= 0.26 sec; P<0.01) and swing phase (Pre=0.37 sec, Post= 0.33 sec; P<0.01) decreased. Trot SL shortened by 6 wk (Pre=1.68 m, Post=1.55 m; P=0.03). Survey results indicated a higher instance of positive behaviors when tied and during tack up in TXT horses. Both TXT and CON were best represented in the high suppleness category. Control horses were more frequently rated high for suppleness on a circle and ability to track up. Movement vii analysis revealed no other significant parameters.

This preliminary study failed to demonstrate any difference in wound healing variables between treatment groups in this model of second intention wound healing. This was unexpected due to the established effects of UMF 20 manuka honey on wound healing using the same model. This may be due to systemic effects of cannabidiol and study design. Further research into the use of cannabidiol in equine wounds is warranted.

Cannabidiol (CBD) products have gained popularity among horse owners despite limited evidence regarding pharmacokinetics. The purpose of this study was to describe the pharmacokinetic profile of multiple doses of an orally administered cannabidiol product formulated specifically for horses. A randomized 2-way crossover design was used. Seven horses received 0.35 or 2.0 mg/kg CBD per os every 24 hours for 7 total doses, separated by a 2-week washout. Plasma CBD and delta-9-tetrahydrocannabinol (THC) were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) daily through day 10, then on day 14 after beginning CBD administration. On the final day of CBD administration, plasma CBD and THC were quantified at multiple times. After administration of 0.35 mg/kg of CBD, the Cmax of CBD was 6.6 ± 2.1 ng/mL while Tmax was 1.8 ± 1.2 hour, whereas the Cmax for THC was 0.7 ± 0.6 ng/mL with a Tmax of 2.5 ± 1 hour. After administration of 2.0 mg/kg of CBD, the Cmax of CBD was 51 ± 14 ng/mL with a mean Tmax of 2.4 ± 1.1 hour and terminal phase half-life of 10.4 ± 6 hour, whereas the Cmax of THC was 7.5 ± 2.2 ng/mL with a Tmax of 2.9 ± 1.1 hour. Oral administration of a cannabidiol product at 0.35 mg/kg or 2.0 mg/kg once daily for 7 days was well-tolerated. Based on plasma CBD levels obtained, dose escalation trials in the horse evaluating clinical efficacy at higher mg/kg dose rates are indicated.