Plasma and urinary exposure of cannabidiol and cannabidiolic acid in horses following consumption of contaminated feed

Background Cannabidiol (CBD) and cannabidiolic acid (CBDA) are non-psychoactive cannabinoids naturally present in hemp-derived products. While these compounds are prohibited during equine competition, horses may be inadvertently exposed through contaminated feed. Data describing systemic and urinary exposure to CBD and CBDA following such low-dose, involuntary intake are limited. This study aimed to describe plasma and urine concentration-time profiles of CBD and CBDA in horses after consumption of experimentally contaminated feed. Results Twelve Standardbred horses received feed containing low doses (10–15 mg) of either CBD or CBDA twice daily for three days. Neither compound was detected in pre-administration samples. Following exposure, CBD was only sporadically quantifiable in plasma, whereas CBDA was detected in plasma from most horses for up to 48 h. In urine, both cannabinoids were quantifiable in all horses, with CBDA consistently present at higher concentrations and for longer durations than CBD. Maximum observed urinary concentrations were markedly higher for CBDA than for CBD. Considerable inter-individual variability was observed in both plasma and urine concentrations. Neither CBD nor CBDA was detected in plasma or urine for more than four days. Overall, systemic exposure following feed contamination was low compared with doses reported to produce therapeutic effects in horses or other species. Conclusions Low-dose oral exposure to CBD and CBDA, mimicking feed contamination, can result in detectable concentrations of cannabinoids in equine plasma and urine, with CBDA representing the predominant analyte. Although the study was not designed to establish detection times and analytical sensitivity may differ from routine doping control, the findings demonstrate that inadvertent exposure through feed may lead to measurable cannabinoid concentrations despite doses well below those associated with reported pharmacological effects. These results highlight the importance of awareness of potential contamination sources and cautious interpretation of low-level cannabinoid findings in equine biological samples.