Fever Leading to Gastric Ulcers in a Young Horse

Q. - My filly picked up a fever while at the trainer’s getting started under saddle (bloodwork indicated an infection, which my vet said probably caused by a virus). She then went off feed for nearly four days, so I brought her home to rest and recoup. While we didn’t scope her to verify the diagnosis, my vet suspected she had gastric ulcers after the combination of not eating and receiving Banamine paste (flunixin meglumine, a non-steroidal anti-inflammatory drug, or NSAID) for the fever. A course of GastroGard (prescription-strength omeprazole used to treat ulcers, rather than prevent them) helped—she started eating again almost immediately after the first dose. I’m now worried about sending her back into training. Is it likely she will suffer gastric ulcers again when put under the stress of moving to the barn and training? If so, is there any way to prevent ulcer onset?

A. - Your veterinarian is right! The initial onset of fever and loss of appetite at the trainer’s barn was likely due to a viral infection, such as equine influenza (often called flu), equine herpesvirus-1 (EHV-1), or equine rhinitis virus.  These viruses usually cause a fever and variable cough, nasal discharge, and loss of appetite, but in some cases horses show very mild signs.

Gastric ulcers can be a primary disease or can occur secondary to another disease or stressor, such as flu, fever, being off-feed, phenylbutazone (Bute, another NSAID) or Banamine administration, painful musculoskeletal injury, colic, etc.).  It sounds like your horse might have had ulcers secondary to the combination of fever, loss of appetite, and NSAID treatment, and that omeprazole was effective. Also, whatever caused her fever and loss of appetite (probably a virus) ran its course, and the horse improved from infection. 

If you are concerned about reoccurring gastric ulcers when your horse goes to the trainer, then I would recommend treating your horse with UlcerGard (over-the-counter omeprazole at 1 mg/kg, orally once daily meant for ulcer prevention) to prevent the ulcers while your filly is with the trainer. 

Also, be sure that your horse is immunized against the common respiratory viruses (flu, rhino [the respiratory infection caused by EHV-1]), equine rhinitis virus) that occur at horse stables. Horses should be vaccinated at least two weeks prior to being shipped to a training stable to allow for immunity to develop. 

Good luck with your horse and all the best with the training!

Q: My performance mare seemed to change after having a foal. Before the foal, she was hot and sensitive but straight forward to train. After the foal, when we put her back to work, she became moody, spooky, and stubborn. Can being used for breeding change a mare’s personality?

A: Can a mare's personality change after being used for breeding? That is a great question and one I can't answer definitively. Pregnancy hormones and then the presence of a foal at her side might temporarily change a mare's behavior. I have not found any research on point here about long-term changes, particularly with regard to training and performance behavior.

The "common wisdom" is that breeding a mare will make her mellower, but lots of anecdotal reports out there go either way--yes, she changes, or no, she goes back to her old personality after the foal is weaned. But I have some thoughts and questions to consider that might help lead you to an answer about your mare's apparent change in her behavior during training.

I am answering this under the assumption that your foal has been weaned. If not, it is possible your mare's change in behavior is due to leaving her foal behind during her training sessions. Mares are highly individual in their anxiety when separated from their foals, even as the foal ages and they both appear more independent. 

In any mare who has some kind of behavior change, we should always first consider disease of the reproductive tract. Certain ovarian tumors or persistent ovarian structures can definitely cause a behavior change. Uterine infections, even quite severe ones, might not cause any general physiologic or behavior changes, but that's worth considering too. So you might want to have your veterinarian do a reproductive examination on your mare.

Past experiences can affect current behavior, and apparent personality changes could actually be just learned responses. So it's worth thinking about your mare's behavior in detail and how she was handled throughout the time she was being bred, pregnant, and had a foal at side. Were there any changes in who was handling the mare during pregnancy and after foaling? Could she have learned some undesirable behaviors from her interactions with other people? Was she an extremely protective mother? If so, perhaps she learned some behaviors to get people to leave her be, which she's transferred effectively to her riding career. 

Perhaps even a typical level of protectiveness has earned your mare some experience in attention and vigilance that translates to being spooky or stubborn. Consider your mare's current environment. Perhaps now that your mare has experience with a stallion (if she was bred naturally) and having a foal at side, she might behave differently now if she is in proximity to stallions and foals. This might even vary with her estrous cycle.

There are also some simple changes that might have happened over the past year or two that you've probably thought of. Has your skill and experience changed? Do you have a new trainer or instructor who has different expectations of your mare or a different style of training? Has this mare's career changed pre- and post-breeding? A mare coming off of a racing career might show quite dramatic changes in behavior over time with or without being bred. It’s possible your mare's behavior change might just be coincident with another year or two in age and maturity.

I don't think what we know about free-running mares helps much with your specific question. A mare's affiliation with others in her group certainly changes after foaling, with her own foal, as well as her older foals if they are still in the group, generally becoming her closest frequent companions. Mares in a natural breeding group don't usually change their dominance status by virtue of having a foal. Their dominance status might change over time after many foals, but this might just be due to their being older and residing in the group longer.