The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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A29 TheHorse.com/AAEP2017 March 2018 THE HORSE AAEP Wrap-Up SPONSORED BY Can Ovariectomies Be Justified on Behavioral Grounds? When mares behave badly, we can be quick to blame their hormones. And, typi- cally, we want a quick fix. Could removing their ovaries be a viable solution? James Crabtree, BVM&S;, CertEM, MRCVS, di- rector of Equine Reproductive Services, in the U.K., aimed to answer this question. Undesirable behaviors clients often re- port in their mares, said Crabtree, include overt reproductive behaviors, aggression, and, in most cases, difficulty training or an unwillingness to respond to the rider. If the veterinarian confirms hormones are to blame, the question then becomes, "Can we justify an ovariectomy?" To answer this, he found and highlight- ed four important papers from the past 30 years that shine light on the topic: 1. In 1993 Hooper et al. retrospectively evaluated 23 bilateral ovariectomy cases (both ovaries removed), 16 of which were for behavioral reasons, and found that 35% of the mares continued show- ing estrous behavior post-ovariectomy. 2. In 2007 Kamm et al. performed a retrospective study of 35 bilateral and unilateral ovariectomies, 23 of which were for behavioral reasons. Based on survey results, 22% of owners were dis- satisfied with the procedure, primarily due to a lack of behavior changes. 3. In 2007 Hedberg et al. compared ad- renocorticotropic hormone's effect on testosterone and estradiol levels in five mares before and after ovariectomy. They teased ovariectomized mares and found all still demonstrated sexual receptiveness. They also showed more days of estrus than when intact. 4. In 2015 Roessner et al. completed a study of 20 bilateral ovariectomies per- formed for behavioral or performance reasons and compared improvement from altrenogest therapy alone to that post-ovariectomy. The ovariectomies re- sulted in significantly better outcomes than therapy using altrenogest, but 30% of mares still showed estrous behavior. Based on these results, ovaries are not essential for estrous behavior, said Crab- tree. "Ovariectomy might even make the situation worse, as estrous behavior may become irregular or persistent," he said. It's not totally clear why ovariectomized mares continue showing reproductive behavior, but he said it's most likely due to estrogen from the adrenal gland. "If the goal is to change aggressive behavior, an ovariectomy might be more successful," he noted. "It's also more likely to be curative if the cause is ovarian pain." Crabtree listed alternative therapies for controlling undesirable behavior in mares: ■ Progestogen supplements, such as altrenogest (e.g., Regu-Mate). ■ Prolonging the lifespan of the corpus luteum (the structure responsible for producing progesterone post-ovulation) with coconut oil infusions, the hormone oxytocin, intrauterine sterile acrylic spheres, or pregnancy termination. ■ Inducing late diestrus ovulation. ■ Administering a gonadotropin- releasing hormone vaccine or overdose to suppress the hypothalamic-pituitary- testicular axis. The vaccine is only available in Australasia. Overall, he said, such "behavior might be better managed with medical therapy or cycle manipulation. Aggressive mares might be candidates, but explore manage- ment changes or other causes first." Be aware that estrous behavior can persist post-ovariectomy, he said. Removing Uterine Marbles Historically, vets have inserted a marble into a mare's uterus to manage her estrous cycles. The theory? The marble would act like an embryo and trick her body into thinking she was pregnant, thus eliminat- ing estrus-related behaviors. But lack of efficacy and overall negative health effects from prolonged placement have prompted some vets to call for their retirement, said COURTESY DR. JAMES CRABTREE Sterile polymethylmethacrylate spheres are safer than uterine glass balls for estrous suppression. VETERINARY REPRODUCTIVE MEDICINE AT THE CORNELL EQUINE PARK MARE FOALING SERVICE 607-253-3100 The reproductive medicine specialists at Cornell University's Equine Hospital offer close monitoring of your late gesation mare at the Cornell Equine Park , located only minutes from the Hospital. CONTACT US TODAY Pre-Foaling: • Daily physical exams and transrectal/ abdominal ultrasound evaluation of the foal and placenta as needed • Placement of birth monitoring transmitter • Daily turnout • Mammary secrection monitoring At the time of Foaling: • Attendance and assistance (if needed) by Reproductive Medicine veterinarians • Placental evaluation • Colostrum quality evaluation • Physical exam of foal, enema administration • IgG test 12 hours after birth Post-Foaling: • Daily turnout for mare and foal • Twice daily physical exams for mare and foal • Post-foaling reproductive examination of the mare • Easy access to the Cornell University Equine Hospital Video surveillance monitoring throughout the mare's stay We also offer mare breeding services