Case Report: Mother’s little helper

When a mare’s aggressive behavior puts her foal at risk, an anti-anxiety medicine for people helps the pair bond.

By the time the 4-day-old foal arrived at Iowa State University’s Lloyd Veterinary Medical Center last spring, he was on the verge of death.

His dam, a maiden mare named Annie, had rejected him. “Problems with mare-foal bonding are relatively rare,” says David Wong, DVM. “However, this case was an extreme situation in which there was no maternal interest in the foal and the mare would kick and lash out at the foal when he attempted to suckle.”

Annie’s owners had been milking the mare by hand and bottle-feeding the youngster, whom they dubbed “Sam,” but that hadn’t been going well. “Hand-raising a foal is extremely labor-intensive,” says Wong. “Even people with the very best intentions can’t keep up with it. Foals eat three to four times an hour, around the clock. You simply can’t keep up that schedule very long when it’s only one or two of you.”

To further complicate matters, Annie hadn’t been producing much milk. The little bit her owners were able to collect wasn’t nearly enough to sustain Sam. “By the time they arrived at the clinic, the foal was flat out,” says Wong. “He was not moving and was unresponsive to our efforts to get him up. I’m not sure he would have made another day if they hadn’t brought him in.”

Saving Sam was the first priority when the pair arrived at the clinic. “In these situations everyone moves quickly,” says Wong. The initial exam showed that the colt was severely dehydrated with a very low body temperature (89.9 degrees compared to the normal 99 to 101) and a low heart rate (40 beats per minute compared to the normal 96 to 108 beats per minute). The team pulled blood for analysis before starting the foal on intravenous fluids.

“The immediate goal is to support him with fluids until you can get a better idea of what’s going on,” says Wong. “We can get laboratory results back in about a half-hour, but even in that time we needed to do something for him.”

The blood tests showed just how sick Sam was: “He had failure of passive transfer,” says Wong. In other words, Sam had failed to get enough of the antibody-rich first milk, called colostrum, from his dam. A foal’s immune system isn’t fully developed at birth. Until he is able to manufacture his own antibodies to protect against disease, he must rely on those supplied by his dam. In humans, maternal antibodies pass through the placenta: A baby is born with immunity supplied by his mother. In contrast, a foal must nurse in order to have any immune protection.

“There is a limited window during which a foal can absorb these antibodies through the gastrointestinal tract,” explains Wong, “It’s only about 24 hours.” Normally, this allows plenty of time for a newborn to stand and nurse. Annie’s refusal to let her foal nurse, however, combined with her low milk supply, caused Sam to miss that crucial window. His serum immunoglobulin (IgG) level was 400 mg/dl, while a normal foal’s level would be greater than 800 mg/dl.

Sam was also septic: At least two species of deadly bacteria, E. coli and Citrobacter sp., had entered his bloodstream and spread throughout his body. In addition to potentially crippling joint infections, diarrhea and pneumonia, septicemia in foals can lead to shock and organ failure. Depending on how soon treatment begins, and any complications that occur, survival rates range between 30 and 70 percent.

“Sam’s sepsis could have been related to the failure of passive transfer, or it could have developed independently,” says Wong. However, which condition came first hardly mattered at this point. Both had to be addressed immediately if the foal was going to survive.

The treatment for failure of passive transfer is intravenous administration of plasma collected from an adult horse with a robust immune system. “You supply the foal with the antibodies he should have received from his dam,” says Wong. “They are just coming from a different horse via a different route.” Foals can occasionally have adverse reactions to the plasma infusion, but Sam tolerated it well, and his blood IgG levels approached normal within hours.

However, the foal still needed intensive treatment for sepsis. He was started on a combination of intravenous antibiotics, and a nasogastric tube was inserted so that he could be fed around the clock by a team of veterinary technicians who never left his side.

“We kept [the mare] nearby because we didn’t want to interfere with any bond they may have or may eventually form, but she wasn’t at all interested in what we were doing because she really had no interest in her foal,” says Wong.

Even so, the veterinary team was hopeful that the pair would eventually bond and Annie would allow Sam to nurse. With that goal, they gave the mare daily doses of the drug domperidone to increase milk production so she’d be better able to feed her foal when the time came.

Forging a bond

Over time Sam grew healthier and stronger. After four days at the clinic, he was able to stand. Two days after that, he attempted to nurse on his own. Annie, however, still would not allow it. “She would kick out at him or try to bite whenever he made any attempt to reach her udder,” says Wong. “If we hadn’t been there to restrain her, she would have injured him.”

A painful udder can cause mares to discourage their foal’s normal suckling behavior, says Wong, but Annie did not seem uncomfortable when she was milked by hand. “There seemed to be no physical basis for her reaction to him,” he says. “It was psychological—as if her maternal instinct wasn’t there at all.”

Foal rejection has been the subject of numerous studies, but no clear cause has been identified. The problem occurs more often in Arabians than in other breeds and maiden mares are more likely to reject their foals than are experienced dams, but there is no way to predict when rejection will occur. Sometimes, however, it is possible to encourage a reluctant mare to accept her foal.

Wong had handled other cases of foal rejection, and he laid out the typical plan: “The first thing we do is try restraining the mare,” he says. “Sometimes, if we can just have the foal nurse a few times, the mare has a change of heart and they will bond.”

The team put hobbles on Annie so she couldn’t kick and held her head while Sam nursed. Restrained this way, she was unable to hurt the foal, but she still wasn’t happy about him nursing.

Sedation was the next step. “The idea is to sedate the mare enough so she allows the foal to nurse, and then you wean her off the sedative,” says Wong. “Hopefully, as the dose is slowly dropped, she continues to allow the foal to nurse and you’ve solved the problem.” The plan was to give Annie an injection of detomidine every four to six hours. However, even the full dose had little effect on Annie, who continued to try to attack Sam.

Permanently separating Annie and Sam was starting to look like the only recourse. In some cases, a nurse mare may be found for the foal, or the youngster may be raised by hand—but neither of those options were desirable. “You want to try everything you can to keep a mare and foal together,” says Wong. “It’s better for everyone if you can.”

As the veterinary team brainstormed, someone mentioned alprazolam. A psychoactive drug in the benzodiazepine class, alprazolam is sold under several brand names, including Xanax. Often prescribed for people with panic and anxiety disorders, the drug is also used in cats and dogs to treat separation anxiety and related disorders. “It’s been used successfully in other animals, so we wondered what effect it might have in horses,” says Wong. “It’s known to be very safe, so we decided to give it a try.”

Extrapolating the dosage from human and canine literature, the team started Annie on alprazolam three times a day. “Within the first 12 to 18 hours, she was noticeably less upset,” says Wong. Cautious at first, the team continued to keep Annie tied and hobbled while Sam nursed, but over the next two days, they slowly allowed her more freedom. Finally, nine days after the pair arrived at the clinic, Annie allowed her foal to nurse without showing any signs of aggression.

“At that point we actually backed off the dose a bit,” says Wong. “The mare was looking almost too sedate and quiet. She was allowing the foal to nurse but not paying much attention to anything else.” With the dosage reduced to only twice a day, Annie perked up, but she continued interacting with and accepting her foal. The team monitored Sam as well, because the drug was likely being passed to him through his dam’s milk, but he never appeared to be sedated or otherwise impaired.

The happy, healthy and fully bonded pair who returned home presented a very different picture than the aggressive mare and the near-death foal who arrived at the clinic just two weeks earlier. Annie’s owners monitored the mare as they tapered off her alprazolam doses over the next eight days, but they saw no further signs of aggressive behavior. Six months later, as they reported to Wong, both mare and foal were still doing well.

Since Annie, Wong has had similar successes using alprazolam to treat postpartum aggression in other mares. “We’ve also done some pharmacology work, so we can see levels increase in the bloodstream as it takes effect,” he says. Wong recently published a paper on Annie’s case in a veterinary journal so other practitioners might consider alprazolam to manage cases of foal rejection and, possibly, other behavior problems. “I’m hopeful we can use it for other types of anxiety issues,” he says. “It could be a very useful drug.”

Reference: “Use of alprazolam to facilitate mare-foal bonding in an aggressive postparturient mare,” Journal of Veterinary Internal Medicine, January 2015

This article first appeared in EQUUS issue #451, April 2015. 




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