AMBULATORY PRACTICE

How We Select, Prepare, and Maintain a Stimulus/Mount Mare

Kristina Janson Whitesell, DVM*; and Sue M. McDonnell, MS, PhD, CAAB

A stimulus/mount mare that is an , sound, and reliably attractive and receptive to most , as well as comfortable with her work and easy to handle, is invaluable to a breeding facility. Organized and systematic behavior evaluation specific to your clinic’s protocols before selection will reveal undesirable behaviors that may prove unsafe in the semen collection environ- ment or may complicate or prevent successful semen collection. In the case of intact mares, bilateral ovariectomy performed through colpotomy or a hand-assisted laparoscopic approach with colpotomy allows for a short convalescent period compared with other approaches. Additionally, flank sensi- tivity can be avoided by colpotomy. In the absence of functional ovaries, frequent, low-dose supplementation can usually maintain estrus adequate for a stimulus/mount mare. Authors’ ad- dress: School of Veterinary Medicine, University of Pennsylvania, New Bolton Center, 382 West Street Road, Kennett Square, PA 19348; e-mail: [email protected]. *Corresponding and pre- senting author. © 2013 AAEP.

1. Introduction ural cover. Accordingly, a commonly used alterna- Although some stallions, initially or after training, tive to a cycling mare in estrus is a mare without respond adequately for semen collection in the ab- functional ovaries that is administered exogenous sence of a live mare, most semen collection facilities estrogen as needed to maintain estrus at a level do require a live mare to accommodate stallions that sufficient for the needs of the facility. do not respond. A cycling mare in natural estrus In a quantitative study of the behavior of 10 ovari- close to ovulation is typically the most stimulating to ectomized and 10 seasonally anestrus mares, Asa et 1 stallions. However, to ensure availability of a suit- al reported that 17 of the 20 mares showed some able mare in estrus on any given day throughout the degree of receptivity (tolerance of the ’s ap- year, a fairly substantial herd of monitored/cycle proach, teasing, mounting, insertion) on most test manipulated mares from which to choose is typically days. The probability of any particular mare exhib- required. It has long been known that in the ab- iting estrus on any test day in their study was re- sence of ovarian steroid hormones, whether during ported to be 50%. The intensity of estrus observed anestrus, in certain karyotipic abnormal states was comparable to that of mares transitioning be- (XO), in senescence, or after ovariectomy, mares can tween estrus and diestrus phases, which is less in- show estrus sufficient to stimulate response of most tense than is typical of the day before and the day stallions for semen collection as well as tolerate of ovulation. This study also quantitatively con- mounting for semen collection or schooling for nat- firmed the long-time anecdotal observations of wide

NOTES

AAEP PROCEEDINGS ր Vol. 59 ր 2013 23 AMBULATORY PRACTICE variation in the degree of proceptivity (solicitous- Systematic Behavior Evaluation ness), receptivity (tolerance of mounting), and at- If a mare meets those initial behavior and sound- tractivity (stallion sexual response) of mares ness selection criteria, we then systematically eval- without ovarian steroid influence, both among uate her behavioral comfort and compliance with a mares and from day to day within-mare. Only one battery of anticipated breeding shed protocols for of the 20 mares was observed to exhibit estrus on all semen collection, breeding, and schooling of stallions 15 observation days of the study. In a follow-up specific to the environment in which she will be study of steroid hormone treatment of ovariecto- used. Winter anestrus presents an ideal opportu- mized mares, it was demonstrated that estrogen nity for this evaluation because it most closely treatment increased the intensity and decreased approximates the ovariectomized condition. How- variation in estrus as well as correspondingly in- ever, for mares that are not anestrus, we of course creased the intensity and decreased the variation in evaluate the specific breeding shed tasks when she stallion response.2 Estrogen-treated mares showed is in estrus. strong estrus for 80% of the tests and weak estrus Comfort and compliance with tasks specific to the for an additional 3%. Untreated mares showed stimulus/mount mare occupation in our teaching strong estrus in only 23% of tests and weak estrus and clinical environment include tolerance and for an additional 33%. comfort with application of a twitch, breeding cape, This report presents our experience with selection hobbles, breeding boots, and wrap; expression of of candidates for stimulus/mount mares as well as proceptive and receptive responses as well as attrac- preparation and estrogen treatment of ovariecto- tivity to stallions both with and without a twitch; mized mares for comfortable, effective, and safe use easy “steerability” with and without a twitch; ease in an equine reproduction and behavior teaching and comfort with loading, standing for long periods, clinical and research facility with a variety of and unloading in stocks or adjacent the dummy unknown and known stallions of various breeds. mount; absence of tendency for non-receptive or dis- These circumstances necessitate year-round avail- comfort responses (striking, squealing, biting, kick- ability of reliable stimulus mares that are also com- ing, striking, “bunny hopping,” rearing, slapping or pliant with mounting for semen collection, novice swishing tail, moving away, pinning ears, tensing stallion schooling, and a variety of other reproduc- up, cowering) even with prolonged teasing; tolerance tion teaching exercises involving rotating staff and of mounting by a test stallion wearing an “apron” students of various levels of handling ability and (for teaching purposes). We aim to evaluate the stallion and mare response with stallions of various breeding experience. ages, experience, breeds, and breeding tempera- ments. Because we are a teaching facility with 2. Candidate Selection day-to-day variation in the handling team, we also try to assess the candidate’s cooperation and comfort Initial Considerations with handlers of various skill levels and handling When considering particular mares as candidates styles. A particular concern is to identify behavior for preparation to be a stimulus/mount mare, we that would pose safety threats for less experienced first try to identify candidates with (1) a behavioral student handlers in a teaching environment. Fig. 1 history of excellent temperament and interaction illustrates an example check sheet that we use to with humans and other , both for general record test session findings. Fig. 2 includes a series ground handling as well as when interacting with a of images from a candidate evaluation session. stallion for estrus detection or breeding, and (2) generally good health, soundness, and ease of main- 3. Preparation taining good body and particularly foot condition. The goal of a dedicated stimulus mare is to remove We also consider the age of the mare because there the limitations of cyclicity and seasonality encoun- is considerable effort and expense to preparation, tered when selecting mares to aid in semen collec- and we prefer to expect as many years of service as tion. This can be achieved through ovariectomy possible. Although there are no data to confirm the and subsequent estrogen replacement or estrogen concepts, we consider the tendency for (1) demon- replacement alone for mares with non-functional strative estrus for several days each cycle and (2) ovaries. less frequent and demonstrative aggressive re- sponses to stallions during diestrus to be predictive Ovariectomy of better performance and comfort as a stimulus/ Various approaches for ovariectomy in the mare mount mare. If this history is known, we certainly include colpotomy, flank laparotomy, paramedian take it into consideration. Also, because of our ex- celiotomy (oblique or caudal), ventral midline celiot- perience with apparent color, breed, and size pref- omy, and various laparoscopic techniques, either erences and aversions among stallions, we aim to conventional or hand-assisted as summarized by maintain a variety of these characteristics among Loesch and Rodgerson.3 A complete discussion of our available stimulus/mount mares. surgical technique is beyond the scope of this report;

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Fig. 1. Example check sheet for systematic behavior evaluation of stimulus/mount mare candidates. however, consideration of the implications of the scopic approach carries the advantage of improved various approaches for intended use as a stimulus/ visualization of the ovary and mesovarium over mount mare is warranted. Flank incisions not only the flank approach, extension of portal incisions to require an extended convalescent period (4 to 6 facilitate extraction of the ovary is still necessary. weeks), but, in our experience, flank incisions often Therefore, postoperative healing time, incisional result in an aversion to flank contact that not only complications, and persistent flank sensitivity are complicates mounting by a stallion for semen collec- concerns for a stimulus/mount mare. Recently, tion through the use of the artificial vagina or as an hand-assisted techniques have been developed to intermediate training step but also seems to predis- combine the laparoscopic visualization with ovary pose some mares to be less tolerant of vigorous pre- extraction by means of colpotomy to minimize flank copulatory interaction. In contrast, for colpotomy, incisional length and consequently, convalescent the convalescent period is only 2 weeks (or in our time. For such techniques, a chain ecraseur or experience less if necessary), and there is no exter- vessel sealing/tissue dividing instrumenta has been nal scarring.4 Although a conventional laparo- used for transection and hemostasis of the mesovar-

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Fig. 2. Systematic evaluation of a stimulus/mount mare candidate: The mare demonstrated difficulty accepting twitch application, repeatedly escaping the twitch even with two skilled handlers (A); initially appeared fearful of the breeding cape but later acclimated (B); loaded easily into stocks (C); tolerated subcutaneous injection (D), tail wrap (E), and perineal washing (F); appeared comfortable standing unattended in stocks for approximately 5 minutes (G), after which she became fidgety and appeared anxious; showed estrus to a stallion initially (H); however, when the stallion was allowed more vigorous close contact, she became less tolerant (I), after which she appeared to panic and attempted to escape.

26 2013 ր Vol. 59 ր AAEP PROCEEDINGS AMBULATORY PRACTICE ium.4–6 The use of this combined approach re- schedule but then becomes increasingly difficult to moves inherent risk of a traditionally blind work with or off-putting to the stallion, a return to a colpotomy approach while minimizing concerns as- better response can typically be achieved by discon- sociated with flank incisions. However, other po- tinuing treatment for a brief period. As little as a tential complications from colpotomy, including few days to 1 week off before return to estrogen peritonitis, eventration, intra-abdominal adhesions treatment has been effective. After the break, we to the vagina, and damage to the cervix, bladder, or resume treatment with the initial three 0.50-mg bowel, are not circumvented. doses. Some mares as individuals may benefit from time off treatment (and work). We have also found Estrogen Treatment that for rare instances, when it is judged that addi- Anecdotally, there seems to be wide variation in tional estrogen may be helpful on short notice, es- estrogen treatment protocols used to maintain ade- trogen can be applied intravaginally, with what quate estrus in stimulus/mount mares. Ginther7 appears to be positive effects within 2 to 4 hours. discussed heightened sensitivity of anestrus mares Hyperemia of the vaginal mucosa generally follows to low doses of estrogens, citing early work done by intravaginal topical application, which typically re- Nishikawa demonstrating a minimum effective dose solves within a few days at most. Nonetheless, be- of estrone for induction of estrus to be 50 mg. cause of this untoward side effect that could be Estrus was seen as early as 4 hours and no later counterproductive to receptivity, we reserve the vag- than 10 hours after administration, and the dura- inal topical route of administration for rare situa- tion of estrus ranged from 3 to 10 days. Ginther tions requiring a rapid improvement in response. also discussed estrogen supplementation in ovariec- tomized mares, citing work done by Hillman admin- Experience/Training istering 0.5 mg or 5 mg of estradiol to mares that Despite careful selection and preparation of candi- resulted in interest to a stallion within 3 hours and dates, not all meet the challenges of our facility. maximal estrus response in 9 hours. Mares subse- In our experience, stimulus/mount mares can either quently returned to pretreatment behavior in 48 become more or less tolerant and comfortable with hours for the 0.5-mg dose and 96 hours for the 5-mg time of service. Some appear to improve with posi- dose. Daily estradiol treatment at 1 mg/day re- tive experience. Some can become less comfortable sulted in positive estrus signs for the duration of and willing, possibly because of frequency and in- administration. Of the two forms of estrogen with tensity of use, temperament of particular stallions, which we have extensive experience with ovariecto- and experience with handling styles. mized mares (estradiol cypionate and estradiol 17- ␤), we have found estradiol 17-beta in oilb to References and Footnotes typically result in more reliable, consistent, and full 1. Asa CS, Goldfoot DA, Garcia MC, et al. Sexual behavior in complement of estrus responses that more reliably ovariectomized and seasonally anovulatory pony mares elicits positive stallion response. On the basis of ( caballus). Horm Behav 1980;14:46–54. early success in maintaining good response for 2. Asa CS, Goldfoot DA, Garcia MC, et al. The effect of estra- diol and progesterone on the sexual behavior of ovariecto- mares used in our research program, the estrogen mized mares. Physiol Behav 1984;33:681–686. treatment regimen that our clinical facility has ad- 3. Loesch DA, Rodgerson DH. Surgical approaches to ovariec- opted for use with average size light horse stimulus/ tomy in mares. Compendium 2003;25:862–871. mount mares, whether ovariectomized or with 4. Smith SE, Devine DV. Hand-assisted laparoscopic ovariec- ␤ tomy and colpotomy in standing mares. Vet Surg 2013. doi: dysfunctional ovaries, is 0.5 mg estradiol 17- ad- 10.1111/j.1532-950x.2012.01007.x. ministered subcutaneously every other day for the 5. Tate LP, Fogle CA, Baisly CS, et al. Laparoscopic-assisted first three doses followed by 0.25 mg administered colpotomy for ovariectomy in the mare. Vet Surg 2012;41: subcutaneously every other day for maintenance. 625–628. It is our experience that the majority of mares (es- 6. Pader K, Freeman LJ, Constable PD, et al. Comparison of transvaginal natural orifice transluminal endoscopic surgery timated three of four) maintain a strong estrus re- (NOTES) and laparoscopy for elective bilateral ovariectomy sponse at this level fairly long term (several weeks in standing mares. Vet Surg 2011;40:998–1008. to many months, in some cases). Certain larger 7. Ginther OJ. Sexual behavior. In: Reproductive Biology of mares may do better with slightly higher doses. the Mare: Basic and Applied Aspects. 2nd edition. Cross We have found that less frequent treatment with Plaines, Wisconsin: Equiservices Publishing; 1992:97–98. higher dosage typically results in less consistent aLigasure, Covidien Surgical Solutions Group, Boulder, CO estrus and may result in stallion-like behavior. 80301. We have also found that in the case of a mare that bEstradiol 17-␤, 3.33 mg/mL, Hagyard Pharmacy, Lexington, initially performs well with the low, frequent dose KY 40511.

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