Researchers at LSU’s School of Veterinary Medicine set out to identify possible side effects of feeding CBD to horses for an extended period. The trial lasted 56 days and, in the end, investigators found no problematic changes in balance, coordination, mental alertness, or body chemistry. Presenting author Michael St. Blanc, DVM, explained the study’s methods and conclusions at the 2021 American Association of Equine Practitioners Convention, held Dec. 4-8 in Nashville, Tennessee.

The research team brought 20 university-owned Thoroughbred geldings in from pasture, gave them two days to acclimate, and then randomly assigned each one to either a treatment or control group. The horses were examined, had their blood chemistry analyzed, and were given sedation (alertness) and ataxia (coordination) scores to establish individual baselines. The study was blinded, so investigators would not know which horses would be receiving CBD and which ones would not.

SmartPak provided its Smart & Simple CBD Pellets containing 150 milligrams of CBD per scoop—(the recommended daily dose). The control group received a placebo with identical ingredients minus CBD and hemp oil (the latter listed as an inactive ingredient in the CBD pellets). Two hours after feeding, observers watched the geldings and assigned ataxia and sedation scores. They did this after the horses received the first dose and weekly thereafter. They also weighed the horses each week and performed thorough physical exams and bloodwork again at Days 28 and 56 of providing the supplement.

Nineteen horses completed the trial. (One gelding was pulled from the study two weeks in due to an unrelated health issue)

Throughout the study, the three investigators who assessed the geldings for ataxia and sedation strongly agreed, upon comparing their independent scores, there were no significant differences between the two groups. Balance, coordination, and alertness did not change noticeably in individual horses, even while CBD blood plasma levels became detectable in more horses as the study progressed (four out of 10 after the first dose, compared to seven out of nine on Day 56).

Two geldings in the treatment group did experience a “mild colic” that resolved quickly. Those clinical signs were not identified as side effects of ingesting the CBD supplement, St. Blanc said. Two of the horses in the control group also required veterinary attention, one for an esophageal obstruction and the other for a facial laceration—just horses being horses, he added.

St. Blanc has not completed a deep dive into the research group’s blood chemistry findings, but he said they saw no changes of concern. Bilirubin counts and enzyme tests indicated that the horses’ kidneys and livers were functioning just fine on 150 milligrams of CBD a day. He did point to the need for further studies that would establish guidelines for safe and effective dosing. Recommendations vary significantly between CBD products. In the LSU study, horses were given approximately 0.3 milligrams per kilogram of body weight with no ill effects. That gives us a valuable—and scientifically tested—starting point.