Effects of oral supplementation of cannabidiol on stallion spermatogenesis

Cannabidiol (CBD) is gaining popularity in the equine industry since the declassification of hemp in the 2018 farm bill. Cannabidiol, a chemical derivative collected from the plant Cannabis Sativa L., does not have the psychoactive effects of THC, and has a longer half-life. The endocannabinoid system, discovered in the 1990s, is made up of 2 main receptors: cannabinoid receptor subtype 1 (CRN1) and cannabinoid receptor subtype 2 (CRN2). Cannabinoid receptor subtype 1 has been identified in stallion reproductive tract organs including the testes, vas deferens, and prostate gland. Anandamide (AEA), and 2-arachidonoyl glycerol (2-AG), are 2 main endocannabinoids naturally secreted within the body and may have effects on reproductive processes. Although it takes high amounts of the ligand, it is thought that cannabidiol may influence the CB1 receptor. This study was conducted to determine the effects of daily oral supplementation of CBD over 90 consecutive days on seminal parameters in young stallions. Eight, 2-year-old stallions were blocked by weight and assigned to either control (CON; n = 3) or treatment (CBD; n = 4). The treatment group was administered CBD oil (0.6 mg/kg BW), while the control group was given olive oil (0.6 mg/kg BW). All horses were weighed weekly to recalculate dosage rates. Blood samples were drawn weekly via jugular vein puncture for CBD and testosterone level analysisthrough TVMDL lab systems. Stallions were acclimated and trained to collect using artificial vagina for 3 weeks leading up to first sample collection. Semen samples were collected twice weekly and immediately evaluated using a computer assisted semen analysis machine to quantify motility, concentration, and velocity rates. Data was evaluated using Statistical Program (R Core Team, 2022) as an ANOVA with repeated measures to determine effects of treatment on static velocity, rapid velocity, and testosterone levels. Results were considered significant at P < 0.05 and were considered a trend at P ≤ 0.15. Rapid velocity and static velocity were consistent in cell numbers; however, over time static velocity did show a slight numerical increase in static cells in the CBD treatment group (P ≤ 0.0874);(CBD = 270.7+-36.79, CON = 315.0 +-44.35). Average weekly testosterone levels did not differ among stallions; yet tended to decrease by week (57.03 +-9.927 ng/dl and 46.95 +-5.151 ng/dl respectively);(P ≤ 0.0749). These findings indicate that cannabidiol, had no effect on stallion spermatogenesis when fed at 0.6kg/mg consecutively for 90 d. Further research should evaluate cannabidiol effects over a longer period and with different ages of stallions.