The veterinarians at the University of Pennsylvania’s New Bolton Center regularly evaluate mares for suspected ovary-related behavior issues. In most cases, however, they find the root cause is something else entirely.

Sue McDonnell, PhD, CAAB, adjunct professor of reproductive behavior and founding head of the University’s Equine Behavior Program, has been evaluating these so-called problem mares for decades. At the 2017 American Association of Equine Practitioners convention, held Nov. 17-21 in San Antonio, Texas, she described how the team at New Bolton Center, in Kennett Square, evaluates them and shared some case examples.

“Diagnosing the root causes (for behavior problems) is important for welfare, safety, and client satisfaction,” she said.

When evaluating a mare whose owner complains of “marish” or “hormonal” behavior, McDonnell said she first obtains and views a 24-hour video sample of the horse in its stall. During this period, she will watch for behavior patterns suggesting the mare is in discomfort, such as tail- or hip-rubbing, udder-nuzzling, kicking at walls, etc.

She might also present the mare with social “challenges” such as feces from other mares or stallions, teasing, or mares in estrus as well as diestrus (the period between heat cycles). The mare’s behavior often suggests the type and location of discomfort, giving clinicians some direction for diagnostic examinations, such as reproductive and endocrine exams, lameness evaluation, diagnostic imaging, neurologic exam, gastroscopy, or even dental.

“More often than not, with cases referred for an ovariectomy (removal of the ovaries) the root cause of discomfort has nothing to do with the ovaries,” said McDonnell. Examples of actual causes of problem behaviors she said were initially attributed to ovarian function include gastric ulcers, impaction colic, enteroliths, uterine adhesions, vaginitis (vaginal inflammation), mastitis (mammary gland inflammation), strangulating abdominal lipomas (fatty tumors), uroliths (bladder stones), sleep deprivation, headshaking syndrome, and musculoskeletal pain.

McDonnell then described a few cases that have come to the New Bolton Center clinic as ovary issues that the veterinarians ultimately diagnosed as something entirely different.

Case 1

The owner of a 7-year-old Thoroughbred hunter/jumper said the mare was refusing to canter, balking at jumps, exhibiting stallionlike behavior, being pushy, and reacting explosively during trailering. Upon arriving at the clinic, the mare panicked and exploded out of the stocks.

While observing her behavior, McDonnell noted that this mare would have kicking episodes, pull her hind limbs up to her abdomen, perform deep abdominal stretches, paw, stamp, gaze at her abdomen, display male-type behavior such as the flehmen response, nip at her chest, and stop eating and resting suddenly.

“Sudden interruption of eating and resting is a really good indicator of discomfort,” she noted.

After various diagnostics, the veterinarians discovered an adhesion on her bladder to the surrounding organs. They later also diagnosed and removed a granulosa cell tumor from her ovary, which could have been to blame for the stallionlike behaviors. While her physical discomfort disappeared after veterinarians treated these issues, McDonnell said she remained nervous in confined spaces.

Case 2

A 16-year-old warmblood mare who, after having been an agreeable family horse her entire life, suddenly became aggressive and untouchable behind her shoulder.

Video evaluation of her behavior revealed around-the-clock signs consistent with abdominal discomfort (e.g., tail-slapping, weight shifting, looking at her sides, interrupted eating and resting, frequent deep abdominal stretches). Eventually, veterinarians diagnosed the cause of her discomfort as gastric impaction. At the time, it was the largest the clinicians had ever seen, said McDonnell.

Case 3

A 7-year-old Thoroughbred mare who, for the past two years, beginning in late October, would become frantic before morning turnout. Her owner reported that she would weave, chew wood, resist leaving the barn, become difficult to release, run to the corner of her pasture, and tremble. She was also nervous and nippy during grooming and tacking. This would last through late spring, when the behavior issues disappeared until the following October.

The veterinarians considered performing an ovariectomy. But after a careful behavior evaluation, they determined the root cause of her behavior was static electricity. She was extremely static-electricity-sensitive, which coincided with the months of the year she wore a blanket.

These cases are just a few classic examples of the many mares that get referred to the New Bolton Center for ovariectomies, said McDonnell. “Two-thirds to three-quarters of the cases that come in for an ovariectomy, an ovariectomy would not have alleviated the discomfort,” she said. “There were other, often multiple, root causes.

“Accurate diagnosis is important to successful resolution of the problem, with significant implications for horse welfare and client satisfaction,” she added.