More Than a Bad Habit
- Jul 1, 2006
Many horses are kept in an unnatural environment--confined in stalls or small pens. Some of them resort to repetitive behaviors such as cribbing, weaving, or stall walking. Most of these horses are fed concentrated, high-energy rations they consume quickly, leaving them with lots of energy, but little to do. Horses raised on pasture, grazing continually on high-fiber, low-energy feed, are less likely to develop these habits.
Cribbing is an activity in which a horse grips a horizontal surface such as a rail, fence, or stall manger (in earlier years called a crib, thus the name of the problem) with the top incisors. The horse anchors his top teeth over the object or presses them into the wood, letting the lower jaw hang slack. He then flexes his neck, opens his throat, pulls back with his mouth open, and swallows air with a grunting sound.
The cribbing horse wears down his top incisors (the teeth often become so worn the top and bottom incisors do not meet when the mouth is closed), and he develops unsightly large muscles under the neck. This can interfere with proper head flexion when ridden.
Serious cribbers can lose weight; they become so addicted to their habit they prefer to crib than eat. Destruction of facilities is a frustration to horse owners. Once the habit starts, many horses keep cribbing--even if given access to pasture and grass. They kill trees, damage fences, and destroy stall dividers and feed boxes.
Prevention vs. Cure
Bonnie Beaver, DVM, Dipl. ACVB, of Texas A&M University, says it is much harder to stop cribbing than to prevent it in the first place. "People keep horses confined and forget they have certain needs," she says. "High-quality feed creates a high energy level, yet at the same time these horses must stand in a stall. When a horse has that much energy, he's going to do something to get rid of it--walking in circles, weaving (constantly shifting weight from one front leg to the other), or cribbing.
"Some horses, as they become nervous, are more mouth oriented than others," Beaver continues. "Some will lick, or flip water, but many will bite on whatever is handy."
Simple wood chewing can progress to cribbing if horses are continually confined. The more they do it, the more they are programming the brain to do it. At that point, they want to continue doing it, even when you get them out of the confinement.
"If you turn them out in a pasture some may stop cribbing, but if you stress them again, that's the first thing they do," she says. "And some won't stop; out in the pasture they'll put their mouth on a fence plank or any other solid surface and stand there and suck air."
Beaver recommends that if a horse is confined, find ways to enrich the environment so he won't start an unwanted behavior. Let him spend half of each day outside, even if it's at night. "Horses need room to graze, run, and interact with other horses, even if it's only across the fence," advises Beaver. "Social interaction relieves the stress of confinement. They need daily exercise to help get rid of extra energy, and a change in diet so it's not so high in energy." Instead of alfalfa hay, feed timothy, coastal, or some other type of grass hay, and cut down or eliminate the grain.
"Horses tend to pick up unwanted behaviors when they are young because youngsters have high energy levels," says Beaver. "Certain bloodlines are more prone to develop problems. Hot-house horses, raised in stalls and blankets, under lights, etc., are apt to start cribbing early."
It's been thought that horses pick up the habit by mimicking others, but this is difficult to prove; they might pick it up just because they are in the same unnatural environment, she says.
If the horse must be in a stall, give him something to do. Toys (big balls or plastic jugs to play with) or a companion animal might help. "The best alternative is to get horses outside where they can move around," says Beaver. "In a paddock, you can spread hay out in small piles so they can go from one to another, similar to grazing activity.
"Working with the horse daily is helpful, giving him something to think about so he won't be bored," she says. "Riding in different environments, or being ponied if the horse is too young to ride, gets him out and looking at other things. I can't overemphasize the importance of prevention. The horse has an active mind and we need to keep it busy."
Attempts to Halt Cribbing
Horse owners have tried many ways to halt cribbing activity, such as covering stall surfaces with rounded metal edges a horse can't grab on to crib, shock collars, and cribbing straps. The latter are fastened around the throatlatch and adjusted to cause discomfort when the horse cribs--making it painful to tense the muscles that retract the larynx. Many straps are fitted with a heart-shaped piece of metal or stiff leather under the throatlatch. When the horse arches his neck to suck in air, the strap tightens and the point of the metal piece jabs him--making him put his head forward again so he can't swallow air.
The strap is not a solution; the horse will resume cribbing whenever it is removed. It is also a nuisance, as it can rub out the mane, wear hair off the throatlatch, or create sores. Wearing the strap all the time can also pose risk to the horse if it ever catches on anything. "Once a horse's brain is hard-wired to crib, these attempts to halt cribbing won't work," explains Beaver. "You are treating the symptom and not the cause.
"With a shock collar, for instance, you are punishing the behavior, but not giving the horse an alternative, and he doesn't know why he's being punished," she says. "If you got zapped every time you coughed, you might try to hold it in, but you still have to cough. The punishment is not addressing whatever is making you cough."
Surgery to remove various portions of the three major neck muscles (on the underside of the neck) used in cribbing is sometimes done to keep a horse from arching the neck to draw in air, with a neurectomy to remove a small portion of the nerve on both sides of the neck that supplies the largest of the muscles. Some owners choose this option for a confirmed cribber that can't be halted using traditional methods, but it doesn't always work.
Surgery for Cribbers
Surgery, until recently, was successful in only 60% of cases, and it sometimes left a horse disfigured. Some horses eventually began cribbing again even if they halted for a time, with the horse recruiting other muscles to participate in the action. Neurectomy worked best if done when the habit was just starting. Newer surgery methods, however, have made this a more successful option.
Daniel J. Burba, DVM, Dipl. ACVS, professor of equine surgery at Louisiana State University Equine Health Studies Program, uses laser surgery for cribbers. This method gives a higher success rate because it is performed on the muscles in a more forward location--decreasing the possibility of the transected muscle ends growing back together (a problem that sometimes made earlier surgeries a temporary solution).
This new technique is a revision of the modified Forssell's procedure, developed several years ago. Burba says, "Dr. Forssell originally developed a method where the ‘strap muscles'--the paired muscles under the throat (sternothyroideus, sternohyoideus, omohyoideus, and sternomandibularis)--were transected. A section was taken out of all those muscles.
"Forssell later revised the technique because of the unsightly effect it created," continues Burba. "Instead of cutting the sternomandibularis on each side of the neck, he transected the motor nerve to those muscles. This procedure has been used for a number of years, but with only a 75-80% success rate."
Some of the horses went back to cribbing because the two ends of the muscles eventually reconnected with development of fibrosis. "So we went a step further and did two things," he says. "We take out more muscle; our transection is more forward, under the jaws, right at the hyoid apparatus, rather than over the throat area. Also we take out a 34-centimeter section that includes all three pairs of muscles and transect the motor nerve (the spinal accessory nerve) on each side of the neck."
The incision is made between the jaws and goes a third of the way down the neck.
"We use a laser to transect these muscles and nerves," he adds. "This reduces bleeding. The cosmetic aspect is also much better; the horse has a much cleaner throatlatch area. A lot of horses develop very thick muscles in the throatlatch area from the cribbing activity, and this is resolved--there's no longer a thick muscle under there, obviously."
Burba said they first started using the laser for these surgeries in 1994. "So far, we have done nearly 60 surgeries and have kept track of the horses afterward," he says. "Right now we are running at about a 91% success rate; very few of the horses have returned to cribbing. We feel the reason for this success is the more forward transection of the muscle, creating a greater gap so muscle ends cannot fibrose back together. Using a laser, which reduces the post-operative bleeding, also helps.
"Bleeding can lead to a clot, which can end up as a fibrous tissue," he adds.
The surgeons now do more closure in the dead space that occurs when they take the muscle out. They draw the muscles that aren't removed from the underside of the neck closer together and suture them down. That helps reduce serum buildup and drainage.
"We still use a drain--put in at the time of surgery and left in for about five days," he says. "We use an active drainage system rather than one that relies on gravity. The tube within the tissue has holes in it to collect the serum, and a tube coming from it has a suction bulb on the end. Thus we can keep negative pressure on it. We try to pull as much of that serum out as we can, and this reduces the amount of swelling."
Burba has performed the procedure on horses from yearlings up to 12-years-old. The average age has been about five years old, with an equal number of males versus females. "Of the 60 horses we've done, 36 have been Quarter Horses, because they represent the majority of the horse population here," says Burba, with the rest being Thoroughbreds, Warmbloods, Saddlebreds, and Morgans.
"Cribbing is a habitual action, and we have not changed the mental aspect (the horse would still crib if he could)," explains Burba. "We just take the physical aspect away." The horse is no longer physically able to perform the action since he doesn't have the muscular structure to keep doing it. The horse probably tries, but can't do it, and after a while he resigns himself to not doing it, notes Burba.
"There is no effect on the horse's performance, head and neck flexion, etc.," following the surgery, says Burba. "He just can't get into position to crib."
The laser surgery holds more promise as a "cure" than other methods and is a more permanent solution. "It is a little involved because of the amount of muscle we are taking out, so we usually keep the horse here a few days in our hospital," says Burba. "We keep the drain in for four or five days, pull it out, and at that time usually send the horse home. Once the skin is healed after staples are taken out (about two weeks), the horse can resume training."
It is better--and easier--to prevent a horse from starting the habit of cribbing than it is to stop that habit. Prevention includes giving horses room to move around or regular exercise, distractions if they must be stall-bound, and feeding regimens that reduce the amount of energy in the diet. There are no cures that work 100% of the time, although the new option of laser surgery might give chronic cribbers a second chance if their fate with their current owner depends on them not cribbing.
Horse Behavior--Endorphin Addiction
Rhythmic actions (such as weaving, stall walking, and cribbing) performed by a confined animal develop in response to stress and are a type of obsessive-compulsive behavior that is difficult to halt. When a horse develops a compulsion, it's a clue that his needs for social interaction, security, mobility, natural feeding behavior, etc., are not being met. Once established, however, the behavior becomes a need in itself, and the horse insists on continuing it.
Twenty years ago, scientists at Tufts University led by Nicholas Dodman, BVMA, MRCVS, DVA, MAPBC, Dipl. ACVA ACVB, discovered why horses crib and why the habit is so persistent. Whenever an animal or human is stressed and engages in some type of repetitive activity as an outlet for pent-up energy, morphine-like proteins called endorphins are released in the brain. The constant activity triggers the endorphin release. The animal will keep up the habit even when no longer confined or stressed because he finds that repeating the pattern produces these calming "opiods" that suppress pain and create a pleasurable sensation.
Horses seem relaxed after a cribbing session. As the act of cribbing causes a temporary sedating effect, the horse becomes addicted to his internal chemicals. He craves the endorphins and gets his "fix" by performing the repetitive behavior. Some horses will actually stop eating and crib during the middle of a meal. This behavior is truly an addiction rather than just a "bad habit."--Heather Smith Thomas
About the Author
Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.
POLL: Big Spender