Effects of SpermAid on Stallion Sexual Behavior

Erin M. Dahill and Sue M. McDonnell
Equine Behavior Laboratory
University of Pennsylvania School of Veterinary Medicine

    SpermAid is an herbal supplement being marketed to increase fertility and libido in stallions. It is also purported to increase testicular hormone production. The active ingredients in the compound are spermine and spermidine. These chemicals are phytochemicals found in radish leaves and root, cucumber fruit, and oats. Spermine and spermidine fall into the polyamine chemical class. Their presence is necessary in cells for replication, growth, and differentiation. It is believed that spermine and spermidine are in the semen of most mammals, purportedly produced by the prostate; however, their role in semen is still debated. To date, no objective clinical studies as to the efficacy and safety of spermine or spermidine or the combination treatment SpermAid are available.

    The objective of this preliminary study was to evaluate effects of an herbal supplement commercially prepared specifically for enhancement of stallion libido and testicular function (SpermAid) on sexual behavior and reproductive endocrinology of normal stallions.

    The study was a two-replicate switch-back with baseline, treatment and post-treatment evaluation. Seven healthy, mature stallions were assigned to matched pairs based on housing, age, sexual experience, and baseline values. Each member of a pair was randomly assigned to SpermAid or vehicle only control treatment. SpermAid treatment consisted of 0.025mg/lb/day of spermine and spermidine in corn syrup divided into two daily doses for 2 weeks. Control treatment consisted of equivalent volumes of corn syrup vehicle. The caretakers and experimenters remained blind to treatment assignments. Sexual behavior was evaluated using a semi-depletion model of up to three consecutive ejaculations per trial on a M-W-F schedule. Each stallion was exposed, in hand, to a stimulus mare restrained in stocks. Four stallions were manually stimulated while mounted on a dummy mount or on the ground while three stallions were stimulated using a Missouri style artificial vagina while mounted on a dummy mount. Each stallion was removed from the breeding shed after he had ejaculated three times or after 20 minutes had elapsed without ejaculation. Evaluations were made for 1 week before treatment started, 2 weeks of treatment, and 1 or 2 weeks after treatments had stopped. All trials were videotaped for subsequent derivation of measures of sexual arousal, copulatory efficiency, and endurance. Specific measures included erection latency, mount readiness latency, ejaculatory latency, ejaculatory thrusts, ejaculatory pulses, mounts to ejaculation, and refractory periods. Jugular blood samples were also taken on a weekly basis through all periods of the study. Testicular steroid levels (testosterone, estrone sulfate, and estradiol 17b) were determined using radioimmunoassay (Equitech Labs, Alachua, FL). Serum chemistries were also run on a weekly basis to monitor for side-effects.

    Analysis of variance of specific behavior measures as well as non-parametric rank order analysis of daily overall sexual behavior performance will be used to test the significance of differences between groups and within subjects over time. Should differences due to treatment be found, these would be interpreted as important. Should differences due to treatment not be found to be significant, larger numbers of subjects and longer treatment periods will be tested before concluding that there are no differences due to treatment.

Erin Dahill is a native of Providence, Rhode Island. She is currently a member of the Class of 2003 of the University of Illinois College of Veterinary Medicine. She was a 2001 Dorothy Russell Havemeyer Foundation Summer Veterinary Student Research Fellow. Erin was a 2000 Havemeyer Fellow ta the James A. Baker Institute at Cornell with Dr. Doug Antczak. Erin is an accomplished equestrian and hunt seat instructor.

Does SpermAid Treatment Affect Spontaneous Erection and Masturbation in Stallions?

Kimberly Unger, Erin M. Dahill and Sue M. McDonnell
Equine Behavior Laboratory
University of Pennsylvania School of Veterinary Medicine

    Within the context of an ongoing study of effects of an herbal supplement, SpermAid, on sexual behavior and endocrinology of stallions (Dahill and McDonnell) we studied possible effects on spontaneous erection and masturbation (SEAM).

    The main study was a 2-replicate switch-back with baseline, treatment, and post-treatment periods. It used five healthy, mature pony stallions that were assigned to matched pairs based on housing, age, sexual experience, and baseline values. At random, each member of a pair was assigned to SpermAid or "vehicle only" control treatment. SpermAid treatment included .025 mg/lb/day of spermine and spermidine in corn syrup divided into two daily doses for two weeks. In this study, the caretakers and experimenters remained blind to treatment assignments. The control treatment was composed of equivalent volumes of corn syrup vehicle. Sexual behavior was assessed using a semi-depletion model of up to three consecutive ejaculations per trial on a Monday, Wednesday, Friday schedule. In addition, each stallion was exposed, in hand, to a stimulus mare restrained in stocks. Four stallions were also manually stimulated while mounted on a dummy mount or on the ground while three stallions were stimulated using a Missouri style artificial vagina while mounted on a dummy mount. Each stallion was removed from the breeding shed after ejaculating three times or until the period between ejaculations had reached 20 minutes. Evaluations were made for 1 week prior to treatment, 2 weeks of treatment, and 1 or 2 weeks after treatments were stopped. All trials were videotaped in order to obtain measures of sexual arousal, copulatory efficiency, and endurance. Jugular blood samples were additionally taken on a weekly basis through all periods of the study for measure of routine serum chemistries and for hormone assay.

    For the current objective of evaluating possible effects on erection and ejaculation, SEAM was observed in the five pony stallions. These observations occurred during replicate 2, in which 2 of the stallions were on SpermAid treatment and 3 were on control treatment. Each stallion was observed for two 2-hour sessions, totaling four hours of continuous observation per stallion. The start and stop time of each SEAM episode was recorded along with the number and type of associated movements and events (dorsoflexion, bounce, press, flare of the glans penis, pre-sperm dripping, thrust, and ejaculation).

    In these limited observations, we found no differences due to treatment (independent t-tests, p > 0.10). Further work with greater numbers and possibly with within-subjects comparisons would be required to conclude that there are, in fact, no effects.

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