Page 78 - November 2021

EQUINE HEALTH
If a young horse must have stall rest, trying to enrich that experience might help avoid problems.
on or play with, using his mouth. These devices are hung in the stall and have apparatus on them to encourage the horse to manipulate them with tongue and lips. The study showed that toys that stimulates chewing, licking and oral behavior is somewhat helpful for the cribber,” says Wickens.
If you watch cribbers, right before they set their teeth on the fence board or side of the stall, many of them exhibit a lot of oral behavior. “They tend to lick and chew just before they actually set their teeth. Some of the horses that live in stalls, if you put a collar on, they stop cribbing momentarily because they can’t expand the larynx and stretch their neck out to try to perform the behavior, but they almost always redirect the behavior into some other form of stereotypic activity. They may start to head toss, weave or walk the stall.” They seem to have a need to express that energy in some way.
The older theory about cribbing was that horses crib to release endorphins, to get their “fix” or a high. “Now we don’t necessarily think they are cribbing to get the high, but perhaps to relieve stress. In younger horses, I think cribbing is initiated in response to gastric inflammation and pain which manifests as stress. We know pain influences brain development in terms of brain chemistry and physiology. I think all these things are linked. Perhaps in these horses their
brain chemistry and physiology are already a little different or becomes altered, so they tend to be more sensitive; their reward and goal-directed systems are different from that of a non-cribbing horse. So when they are fed a highly palatable meal, it tends to stimulate those receptors in the brain to a degree that is more heightened than in a normal horse,” she explains.
“Thus, they crib not so much to get the high. They are getting the endorphin release from something else that’s occurring (like the grain meal) and then that influences the behavior or reinforces it. Cribbing is definitely linked to endorphins and opioid stimulation, but it may be that the receptors in their brain are already more sensitive. Different stimuli that elicit that ‘feel good’ response is reinforcing the cribbing, but I don’t think it’s necessarily the cribbing itself that is giving the horse the fix,” she says.
Wickens hopes to conduct more cribbing research. “We’re thinking that if you allow horses to crib, at least for a period of time during the day, maybe you are helping them reduce stress levels. Horse owners who are trying to manage these behaviors might want to consider this before they try to physically prevent the cribbing behavior.”
She is very interested in the link between gastrointestinal health and stereotypic behaviors,
especially cribbing. The hard part is finding funding for research. “Even though cribbing is a widespread problem and many horse owners are interested in gaining a better understanding of the behavior and how to more effectively manage their horses, finding grant funding to investigate these behaviors is difficult,” says Wickens.
“There are still some groups, especially in Europe, investigating cribbing. Some are going back to the idea of cribbing as a stress-coping mechanism, looking at ACTH and cortisol in these horses. Some of that research has been conflicting, with mixed results, but now that
we have less invasive methods of measuring stress hormones it is easier to do, and results are often more robust. In the past we had to collect blood to analyze plasma cortisol. Now we have methods to look at salivary cortisol and can even collect feces from the horse and look at cortisol metabolites in the feces,” she says.
It’s much better if samples can be collected
in non-invasive ways. “When we have to collect blood via jugular venipuncture, even if a horse is accustomed to handling and veterinary care, if you are drawing blood, you are still introducing a stress just to get the sample. If we can do
this in a non-invasive way it can be helpful,
and there are some research groups using this approach,” she says.
76 SPEEDHORSE November 2021