136 The effects of cannabidiol on libido and heart rate in stallions

Changes in the Agriculture Improvement Act of 2018 increased popularity of Cannabidiol (CBD) as a supplement. Exogenous CBD, derived from Cannabis Sativa L., binds to cannabinoid receptors in the endocannabinoid system. These receptors are located throughout the body, CB1 being prominent in the central nervous system and CB2 in the immune system. Physiological effects of CBD have been well researched but the effects on libido have not. Lack of libido or sexual drive can be detrimental to stallion breeding productivity. The use of CBD as a calming supplement in animals is increasing due to marketing strategies. The study objective was to evaluate libido and heart rate (HR) in stallions given a daily oral CBD supplement for 90d. Two-year old stallions (n = 7) were assigned to either Control (CON; n = 3) or Cannabidiol (CBD; n = 4) treatment groups. CBD was administered at 0.6mg/kg of BW/d, while CON was administered an equal volume of olive oil, as a placebo of similar nature. Treatments were top-dressed over morning feed. Horses were weighed every Monday with dosages recalculated accordingly. Data collections occurred 2x/wk during semen collections with an artificial vagina. Behaviors were previously defined, calmly called out and logged as they occurred. Observations included time spent licking a tease mare, time to erection, time to first mount, and time to ejaculation. A Polar® heart rate monitoring system linked to the KER® ClockItapp was usedto measure HR. Variations of HR included resting HR, teasing HR, mounting HR, step-off HR, and walk-off HR. Data was analyzed using a repeated measures ANOVA within R Statistical Program®(R Core Team, 2022). Results were considered significant at P ≤ 0.05. Throughout the duration all stallions exhibited normal sexual behavior, regardless of treatment. A treatment affect was not seen for licking time between CBD and CON (11.92s ± 3.76 and 0.32s ± 0.20 respectively). There was no difference between CBD and CON for time to erection (27.64s ± 6.84 and 22.9s ± 4.76 respectively). Time to first mount CBD stallions averaged 330.6s ± 23.04, CON stallions averaged 359.5s ± 25.51, with no effect of treatment. Time to ejaculation in CBD stallions was 356s ± 23.78 and 374s ± 24.84 in CON stallions. There were no differences in behaviors over time. There was a time x day effect for walk-off HR(P = 0.04), though this was significant in both groups. No other differences in HR occurred. Long-term use of CBD for young stallions was seen to not affect libido. However, supplementation may lower HR over time. The immediate and lasting response to CBD use in mature stallions and older aggressive stallions is needed to understand the effects of using these products.