Libido, Erection, and Ejaculatory Dysfunction in Stallions

handler education and relatively sim- terone and boost libido. The greatest ABSTRACT Continuous access to mares and ple and inexpensive management improvement in libido with testos- skillful handling are generally the best ap- changes (see Management Conditions terone treatment typically occurs af- proaches to dealing with inadequate libido to Maximize Libido in Breeding Stal- ter 4 to 7 days of treatment. Although in stallions. Although the problem can oc- lions). Housing that provides ample it is often tempting to increase cur in experienced stallions, it is more continuous exposure to mares and re- the dose of testosterone, there is common in slow-starting novices. Erection duced contact with other stallions concern about possible adverse side dysfunction primarily occurs subsequent to traumatic injury of the penis, such as naturally drives stallion endocrinology effects on pituitary gonadal function. kick injuries or semen-collection acci- and behavior in a positive direction.* Personnel must be taught that hor- dents. Ejaculation dysfunction can result Patient, quiet handling in the breed- mone treatment that increases sexual from neurologic and musculoskeletal or ing situation will almost always be behavior is likely to simultaneously ejaculatory apparatus problems. more effective than any other ap- increase aggressive behavior. If the proach. I recommend as little restraint aggression is not anticipated and as safely possible under the particular carefully directed or abided, mare or University of Pennsylvania conditions, as much positive rein- handler interaction with the stallion Sue M. McDonnell, PhD forcement as possible, and avoidance can be counterproductive. Hormone of punishment and negative experi- treatments usually can and should ences. Continuous free-pasture access be withdrawn after a slow-starting exual behavior dysfunction in to mares for several breeding stallions primarily in- days or weeks often al- H Inadequate libido can usually be effectively S cludes libido or ejaculation prob- lows the stallion to gain managed with handler educauon and simple, lems. Libido-independent erection experience and confi- nomic management changes. dysfunction is relatively rare in stal- dence “naturally.” This Limiting mounting attempts, employing pharma- lions and mostly limited to penile almost always enables cologic aids, and other management changes can trauma complications. This column an easy transition to in- reduce the work of a stallion with neurologic- or discusses stallion sexual behavior dys- hand breeding. musculoskeletal-related ejaculation dysfunction. function with a focus on recently de- If results must be Ejaculatory apparatus problems include appar- veloped therapeutic approaches. produced. quickly, ex- ent dysfunction of the neural ejaculatory appa- ogenous hormones to ratus, pain associated with ejaculation, and geni- Inadequate Libido increase circulating tal. tract pathology that may physically impair or The most common type of inade- steroids can sometimes cause pain during ejaculation. quate libido involves slow-starting speed nrogress.2 Short- novice stallions. In most cases, the term treatment with gonadotropin- novice stallion has had a few success- primary cause is simply inexperience releasing hormone (50 ug subcuta- ful breedings. with domestic breeding conditions neously 2 hours and 1 hour before Experienced stallions can also de- rather than physiologic immaturity breeding) or aqueous testosterone velop inadequate sexual arousal; this or an endocrine abnormality. (50 to 80 mg subcutaneously every is often variable rather than consis- The keys to efficient turnaround other day for at least 1 week) can ef- tent. Primary causes for variable or for these stallions primarily involve fectively increase circulating testos- consistent low libido in experienced

SERIES EDITOR nis folding back within the prepuce Management Conditions to Maximize Libido as tumescence commences. Typical- in Breeding Stallions ly, the stallion appears aroused and ready to mount despite no visible General Housing and Care n Provide as much contact (direct, fence line, or in neighboring stall) with erection. The stallion may also ap- mares as possible and as little contact as possible with other stallions. pear uncomfortable or intermittently n Provide ample outdoor exercise and good ventilation when indoors. distracted, pinning the ears, kicking n Keep stallion fit and lean. toward the abdomen, or stepping awkwardly on the hind legs. Close vi- Breeding-Shed Experience sualization reveals a rounded, full- n Provide ongoing in-hand exposure to mares in a breeding situation (I appearing prepuce with the skin recommend one or two 30-minute sessions daily or every other day). stretched taut as the penis doubles q Provide exposure to a variety of stimulus mares in natural estrus, including both quiet and more active mares. Allow interaction with the back on itself within the prepuce. mare’s head, body, and tail; movement of the mare, particularly slow Resolution usually requires removing walking and stopping, is typically more stimulating to a stallion than the stallion from the sexual situation is a fully restrained mare. until the penis detumesces. After the n Provide patient, creative, and skilled handlers who can confidently penis is fully withdrawn, applying a and quietly control a stallion that is showing normal vigorous sexual lubricating ointment to the prepuce behavior. is usually adequate to facilitatesubse- n Allow mounting without an erection; this is a normal behavior of quent normal protrusion. stallions that can be eliminated once the stallion is breeding normally. This situation tends to repeat occa- n Expect an irregular rate of improvement. sionally over time with particular stallions. I have noted this condition to re- breeding stallions include handling Erection Dysfunction peat in stallions that accumulate large changes, negative experience associ- Penile erection in a sexual context amounts of smegma as well as in stal- ated with breeding, a heavy breeding depends on adequate sexual arousal lions in which the penis and sheath are schedule, suboptimal stimulus mares, and a functional pelvic and penile fully cleansed one or more times daily testicular degeneration, musculo- neurovascular apparatus.’ Libido-inde- for breeding. One might speculate that skeletal discomfort, or other. pain or pendent erection dysfunction is rare in this tendency may be related to too illness. It is usually difficult to deter- breeding stallions. The majority of much accumulated “sticky” smegma or mine the causal factors. However, I cases that do occur are subsequent to too little normal smegma lubrication. I recommend treating any suspected traumatic injury of the penis, includ- have seen one stallion appear to suffer discomfort and then proceeding as ing stallion-ring injuries, paralyzed pe- secondary psychologic libido dysfunc- described for a slow novice, review- nis and paraphimosis, kick injuries, tion associated with a relatively fre- ing all possible contributing factors and other ‘breeding or semen-collec- quent occurrence of this event. with the goal of optimizing all as- tion accidents. Artificial-vagina inser- Erection is not requisite for semen pects of the breeding and manage- tion problems are relatively common, collection in stallions with an active ment environment. particularly with “self-serve” dummy libido. Vigorous manual and thermal mounts. Another common semen-col- stimulation of the base of the penis Rowdy Breeding-Shed Behavior lection accident involves penile lacera- typically elicits pelvic thrusting ade- Stallions are by nature quite variable tion associated with the failure to re- quate to achieve ejaculation, either in their level of sexual arousal. High li- move a thermometer from the lumen with the horse mounted or standing 9 bido can be problematic for some of the artificial vagina. on the ground. Pharmacologic aids breeding operations. The handling Although rare, aortoiliac thrombo- to enhance erection or enhance or in- challenge is to safely direct and accom- sis that impairs pelvic circulation can duce ejaculation without erection can modate energetic stallions without dis- result in inadequate tumescence, par- also be useful in prolonging the couraging normal sexual behavior (see ticularly on exertion during mounting breeding life of stallions with inade- Management and Pharmacologic Aids and thrusting. Neurologic disease can quate erection. to Facilitate, Ejaculation). Case reports also be manifest in erection dysfunc- detailing the implementation of these tion (e.g., premature and exaggerated Ejaculation Dysfunction handling recommendations have been tumescence of the glans penis).8 Neurologic and Musculoskeletal published and can be useful reading A potentially confusing type of Problems for most stallion managers.” erection dysfunction involves the pe- Most cases of ejaculatory dysfunc- ment, or using chilled or frozen se- Management and Pharmacologic Aids men can also reduce the work of a to Facilitate Ejaculation stallion (see Management and Phar- macologic Aids to Facilitate Ejacula- To enhance sexual arousal tion). My general approach is to con- n Excellent stallion handling sider and simultaneously implement W Prolonged teasing ,under conditions that yield the highest safe level of as many appropriate aids as possible. arousal m Breeding schedule for maximum arousal m Natural estrus stimulus and mount mares Ejaculatory Apparatw Probhms m Minimal distractions in the breeding area A smaller percentage of ejaculation q Established breeding routine rich with conditioned stimuli for dysfunction cases seem to be specific maximum arousal to the ejaculatory apparatus as op- •l Encouragement and positive reinforcement posed to a musculoskeletal problem n Gonadotropin-releasing hormone (50 ug subcutaneously 2 hours and 1 impairing mounting and thrusting. hour before breeding) Specific diagnoses of primary and q Diazepam (0.05 mglkg via slow intravenous administration) secondary problems are difficult. In To reduce back and hindlimb pain and accommodate musculoskeletal cases of slow or intermittent ejacula- deficiencies tion, ejaculation pattern and semen W Mount mare or dummy of appropriate height and conformation character can suggest further diag- q Excellent physical facilities for breeding (e.g., good footing, head room) nostic procedures. Signs of infection, q Stable (no side-to-side movement) mount mare or dummy occlusion, or urine contamination m Mount mare or dummy placed on a downgrade from stallion to reduce can be followed with ultrasonograph- weight on hindlimbs ic and endoscopic examinations of Semen collection on the ground (artificial vagina or manual stimulation) q the pelvic urethra and accessory sex n Weight loss to reduce work of hindlimbs, particularly during breeding glands. Neurologic problems specific q Lateral support at the hips during mount m Good footing (e.g., grass or dry athletic surface) to the ejaculatory apparatus are sug- m Phenylbutazone (1 g orally twice daily)3 gested by variation in semen pH, con- n Acupuncture and associated therapies4p5 centration, and volume and sperm numbers as well as intermittent urine To increase positive stimulation of the penis contamination of semen and variable W Pressure and temperature of artificial vagina that yields most vigorous ejaculatory pulse pattern and strength. thrusting n Hot compresses applied to the base of the penis * Pharmacologically induced ejaculation can be useful to obtain semen To lower ejaculatory threshold in copula for freezing or as an occasional emer- n Imipramine hydrochloride (500 to 1000 mg orally in grain 2 to 4 hours gency back-up technique for ex- before breeding)2 tremely disabled stallions. *’ Several different protocols are useful (Table One). In their current stage of devel- tion seem tc involve neurologic and at little cost to accommodate special opment, each protocol requires spe- musculoskeletal problems that affect needs of the stallion. One practical cific tedious collection procedures the stallion’s ability to mount and recommendation is to approach each and none is likely to produce ejacula- thrust as the primary cause of breeding breeding or semen-collection session tion in more than 60% of attempts. failure. Musculoskeletal and neurolog- with the goal of optimizing condi- * ic examinations are often difficult to tions for the first mount and confin- interpret because positive findings typ- ing attempts to three or four to limit References 1. McDonnell SM: Stallion behavior and ically do not explain the degree of the wear and tear on the stallion. An- endocrinology-What do we really know? breeding dysfunction. Stallions with other useful technique for disabled hoc 4IstAnnuAAEP MeetA8-19, 1995. musculoskeletal or neurologic prob- stallions is to collect semen with the 2. McDonnell SM: Normal and abnormal stallion standing on the ground, using sexual behavior. Vet C/in North Am lems can continue breeding with ther- Equine Pratt 8(1):7b89, 1992. apy aimed at maximizing libido, re- an artificial vagina or manual stim- 3. McDonnell SM, Love CC, Pozor MA, ducing discomfort, and improving ulation. lo-l2 Pharmacologic aids can Diehl NK: Phenylbutazone treatment in strength and stability during breeding. also be useful in enhancing ejaculato- breeding stallions: Preliminary evidence for no effect on semen or testicular size. There are also a variety of manage- ry function in copula.‘3 Adjusting the Theriogenology 37: 1225- 1232, 1992. ment changes that can be instituted breeding schedule, mare manage- 4. Martin BB, Klide AM: Diagnosis and - --~ TABLEONE Pharmacologically Induced Ex Copula Ejaculation Protocols for Stallions

. Ejucdate Characteristics Latency to Drug (Starting Dose) Compared with Artificial Vagina Ejaculation (min) __------Xylazine hydrochloride’4 Similar l-20 (0.66 mglkg IV) . (usually less than 5) Imipramine hydrochloride13~15~16 Lower volume and higher. sperm concentration, 1 O-60 (2.2 mg/kg IV) , *. . Y* greater total number of sperm, no gel Imipramine hydrochloride Lower volume and highe; sperm concentration, 3-1s (0.75-2 mg/kg PO) followed greater total number of sperm, no gel (after xylazine in 1-2 hr by xylazine administration) (0.3 mg/kg IV)‘* Prostaglandin F,, Greater volume of semen and gel, 5-90 (0.005-0.01 mg/kg IM) similar concentration, greater total number of sperm

IM = intramuscularly, IV= intravenously, PO = orally.

treatment of chronic back pain in horses. Proc 43rd Annu AAEP Highlights (continued from page 195) MeetSO-312,1PP7. 5. Martin BB, Klide AM: Acupuncture for treatment of chronic back pain in horses, in Schoen AM (ed): F/pterinary Acupacturc, Ancient to market specific products (e.g., biologicals) have not Art to Modern Medicine. Goleta, CA, American Veterinary Publica- been embraced by the veterinary profession. tions, 1994, pp 533-542. 6. McDonnell SM, Turner RM, Diehl NK: Modifying unruly breeding behavior in stallions. Compend Contin Educ Pratt Vet 17(3):41 l- What the Future Holds 417,1995. The future of exotic animal medicine must involve not 7. McDonnell SM: Ejaculation: Physiology and dysfunction. Vi-t C/in only private practitioners but also private industry and North Am Equine Pratt 8(1):57-70, 1992. 8. McDonnell SM, Love CC, Martin BB, Reef VB: Ejaculatory failure academia. Veterinary schools should integrate courses on associated with aortic-iliac thrombosis in 2 stallions. JAVMA 200(7): birds and other commonly encountered exotic pets into 9%957,1992. their curricula. Information on the basic physiology of 9. Love CC, McDonnell SM, Kenney RM: Manually assisted ejaculation in a stallion with erectile dysfunction subsequent to paraphimal many exotic animal species needs to be available in text- sis. JAI/MA 200(9):1357-1359, 1992. books, and research into the pathogenesis of exotic animal 10. Crump J, Crump J: Stallion ejaculation induced by manual stimula- diseases remains to be conducted. Such research will need tion of the penis. Tberiogeno&qp 3 1(2):341-346, 1989. 11. McDonnell SM, Love CC: Manual stimulation collection of semen private funding as well as the financial support of practic- from stallions: Training time, sexual behavior, and semen. Tbcrio- ing veterinarians and the public. genoibgy 33(6):1203-1210, 1990. Leaders in the field of exotic animal medicine should 12. McDonnell SM, Pozor MA, Beech J, Sweeney RW Use of manual stimulation for collection of semen from an atactic stallion unable to scrutinize current continuing education (CE) techniques. mount. JAI/MA 199(6):753-754, 199 1. Traditional veterinary education progresses from the nor- 13. Turner RM, Love CC, McDonnell SM, et al: Imipramine treatment mal patient to the diseased patient to clinical management of urospermia in a stallion with a dysfunctional bladder. JA V.&X 207(12):1602-1606, 1995. of the patient. Often current CE emphasizes drug doses 14. McDonnell SM, Love CC: Xylazine-induced m copukz ejaculation in for treatment rather than the pathogenesis of the disease. stallions. TberiogenorogY 36373-76, 199 1. CE lectures rarely define the normal anatomy and physiol- 15. McDonnell SM, Odian MJ: Imipramine and xylazine-induced ex copula ejaculation in stallions. Tberiogenology 41(5): 1005-1010, 1994. ogy of exotic pets. 16. McDonnell SM, Oristaglio-Turner RM: Post-thaw motility and Finally, the future of exotic animal medicine depends on longevity of motility of imipramine-induced ejaculates of pony stal- the willingness of private practitioners to continue de- lions. Tberiogenology 42i475-48 1, 1994. 17. Oriitaglio-Turner RM, McDonnell SM, Hawkins JF: Pharmacologi- manding the best care for their patients. The advances cally-induced ejaculation to obtain semen for freezing in a stallion with made during the past 20 years have allowed exotic animal a spiral fracture of the radius. JAW 206(12):19061908,1995. specialists to manage patients with the same degree of pro- 18. Johnson PF, DeLuca JL: Chemical ejaculation of stallions after the administration of oral imipramine followed by intravenous xyiazine. Proc fessionalism followed in the more traditional companion 44tbAnnuAAEPMeci:12-15,1998. 0 animal practices. cl