CBD for Horses: Study Paves the Way for New Research

By Sechat Editorial

Research reveals that horses are able to metabolize cannabidiol (CBD) without causing adverse effects to the animals. Derived from the Cannabis sativa plant, CBD is a kind of chemical cousin to THC (tetrahydrocannabinol) – but without the psychoactive effects. 

Pharmaceutical companies actively promote CBD products as a herbal way to combat inflammation, reduce anxiety, and provide other potential health benefits. However, the science regarding the safety, efficacy, and appropriate dosage for horses is still seeking concrete answers about the real effects of this substance.

Alicia Yocom, a resident veterinarian in equine sports medicine at Colorado State University (CSU) in Fort Collins, USA, joined colleagues from the institution's Veterinary Hospital to study the absorption of CBD within the bodies of these animals, that is, their pharmacokinetics, while collecting safety-related data. 

She shared these findings during the 2021 American Association of Equine Practitioners Conference, held from December 4 to 8, 2022, in Nashville, Tennessee.

During the study, 12 healthy mares were assigned to a low and high dose group: the low dose horses received 1 milligram per kilogram of body weight, while the high dose horses received 3 milligrams per kilogram of body weight per day for six weeks. These were the highest doses commonly recommended by various CBD supplement manufacturers.

On the first day, all mares received the full dose in one serving. The research team then collected blood samples at eight time points within the first 24 hours to measure CBD levels. They also collected synovial fluid from the carpus (knee) and tested it for CBD at 12 and 24 hours after the initial dosage. 

During the remaining six weeks of the study, the dose was split into two feedings administered 30 minutes after the mares had been fed one kilogram of concentrated feed. 

The reason for giving CBD after this meal, Yocom explained, is that the results of a human study showed that CBD was more bioavailable after a high-fat meal. The mares also received a standard of 2% of their body weight in hay each day.

Researchers monitored the horses daily for changes in attitude, appetite, and fecal production. Every two weeks, they performed physical exams and drew blood, looking for any changes in health, white blood cell count, and blood chemical parameters, including liver enzymes. They also recorded CBD levels in the blood plasma at two and four weeks and collected synovial fluid again at five weeks.

To conclude the study, after the final dose, the team collected blood samples eight times within a 24-hour period. The samples were repeated at 24, 48, and 96 hours after the last dose to determine how long CBD remains in the body with six weeks of cumulative dosing. The researchers collected a final blood sample ten days after the end of the test to assess blood chemical parameters.

Yocom stated that it was confirmed that CBD is bioavailable to horses when administered orally. Physical exams and daily observations also did not detect visible harm – nor any notable behavioral changes – in mares from both groups. 

However, blood chemistry revealed that eight of the 12 horses experienced elevated liver enzymes, which returned to normal during, or shortly after the study ended, for reasons still unknown. 

Another puzzle was a significant drop in blood calcium (known as hypocalcemia) in all 12 mares, although the "ionized calcium" (the calcium in the blood not bound to protein, also known as free calcium) remained within normal limits. The change did not pose an imminent health danger, she noted, and the level returned to normal when the CBD supplement was discontinued.

Yocom shared additional observations that her team gathered from the study:

• > Plasma CBD concentrations tend to peak four to five hours after feeding; therapeutic use can be timed accordingly.

• > The recommended dosing interval is every 12 hours.

• > CBD can remain in the horse's system for 24 hours or more (detectable in some study horses 96 hours after the last administered dose).

• > CBD was consistently detectable in synovial fluid at five weeks when administered at 3 mg/kg, but not at 1 mg/kg, suggesting a cumulative and dose-dependent effect.

• > Equine plasma CBD levels tend to be low compared to those measured in dogs and humans after similar dosing periods.

Based on this new understanding of how horses metabolize and tolerate cannabidiol, Yocum said, researchers will focus future work on determining whether CBD does or does not fulfill its therapeutic promises.