New think­ing about crib­bing

EQUUS - - Equus - By Heather Smith Thomas with Laurie Bon­ner

As re­searchers gain in­sights into this mys­te­ri­ous be­hav­ior, new ap­proaches are emerg­ing for han­dling horses who crib.

Ccom­plaints about horses who crib date back cen­turies. In one 1889 le­gal case, a promis­ing colt was re­turned from Bel­gium to Scot­land on the ba­sis of “un­sound­ness.” Chief among the com­plaints: The colt was a “crib-biter.”

This at­ti­tude wasn’t un­usual: “I have no hes­i­ta­tion in say­ing that a crib-biter is bona fide an un­sound horse…. I ver­ily be­lieve that a crib-biter, sold with a war­ranty of sound­ness, is, to all in­tents and pur­poses, re­turn­able,” wrote T. B. John­son in The Sports­man’s Cy­clo­pe­dia in 1831.

There is no deny­ing that crib­bing can be an­noy­ing. The horse places his up­per teeth firmly on a hard object--be it a fence, stall door, wa­ter trough, or any­thing he can reach---pulls back, arches his neck, and gulps air into the up­per part of his esoph­a­gus with a dis­tinct grunt­ing sound. What’s more, a crib­ber can dam­age walls, fences and other struc­tures around a farm.

Also called wind suck­ing, crib­bing is a stereo­typy---a repet­i­tive, com­pul­sive ac­tiv­ity that seems to serve no pur­pose - and it poses some health risks. Horses who crib may be at a higher risk for some types of colic, and pro­longed crib­bing can wear down a horse’s up­per in­cisors, lead to overde­vel­op­ment of par­tic­u­lar neck mus­cles and cause other phys­i­cal prob­lems. The pres­sures of crib­bing can lead to os­teoarthri­tis of the hy­oid, a small bone in the throat. Some crib­bers lose weight be­cause they’d rather crib than eat.

Un­doubt­edly, most own­ers would like to stop their horses from crib­bing. But that is eas­ier said than done. “With stereo­typ­ies in general, and crib­bing in par­tic­u­lar, no mat­ter what peo­ple have tried, this is a dif­fi­cult be­hav­ior to ef­fec­tively stop once a horse be­comes ha­bit­u­ated to it,” says Carissa Wick­ens, PhD, ex­ten­sion spe­cial­ist at the Uni­ver­sity of Florida. There is no sure-fire cure for crib­bing, and the chances of stop­ping the be­hav­ior di­min­ish as the habit be­comes more en­trenched.

But at­ti­tudes to­ward crib­bing have changed since the 19th cen­tury, and

even just in the past decades, as re­search has dis­pelled sev­eral mis­con­cep­tions about the be­hav­ior. For one thing, the be­hav­ior is no longer called a “vice.” And the fo­cus of manag­ing a crib­ber is shift­ing, from “stop it at all costs” to “re­duce the be­hav­ior, if pos­si­ble, or maybe in some cases/in cer­tain sit­u­a­tions just let the horse crib.”

Crib­bing is no longer an au­to­matic deal breaker when horses are sold, and an in­creas­ing num­ber of peo­ple are will­ing to sim­ply tol­er­ate the be­hav­ior. “Crib­bing can be very chal­leng­ing to man­age, but many of these horses are won­der­ful an­i­mals,” Wick­ens says. “While we con­tinue to shed light on rea­sons why horses crib through ad­di­tional re­search, we are also striv­ing to en­cour­age horse own­ers and the wider equine com­mu­nity to re­al­ize that the horse is not at fault for stereo­typic be­hav­ior.”


Re­searchers still aren’t sure why some horses crib while oth­ers man­aged the same way do not. But most agree that it’s not “con­ta­gious”---horses do not adopt this be­hav­ior by mim­ick­ing oth­ers. “There are many non-crib­bing horses kept in stalls next to crib­bing horses who don’t learn this be­hav­ior,” says Amelia S. Mun­ster­man, DVM, PhD, DACVS, DACVECC, of the Uni­ver­sity of Wis­con­sin–Madi­son.

Sev­eral sur­veys have sug­gested that the ten­dency to crib may be in­her­ited. In one Ja­panese sur­vey, for ex­am­ple, the over­all rate of crib­bing was 1 per­cent among 1,500 Thor­ough­breds but 7 or 8 per­cent within cer­tain fam­i­lies. In a 2009 sur­vey from Cor­nell Uni­ver­sity that in­cluded more than 3,500 horses, 162 (4.4 per­cent) were iden­ti­fied as crib­bers with Thor­ough­breds found to be at higher risk com­pared to other breeds---13 per­cent among Thor­ough­breds and 5 per­cent in warm­bloods and Quar­ter Horses.

It’s pos­si­ble, though, that the higher crib­bing rates seen in cer­tain breeds have more to do with how they tend to be man­aged than ge­net­ics. The cur­rent think­ing is that an in­di­vid­ual horse might have a ge­netic pre­dis­po­si­tion to crib, but the be­hav­ior isn’t trig­gered un­til he is sub­jected to stres­sors re­lated to his life­style.

“Some things that might lead to crib­bing in cer­tain horses in­clude a high-con­cen­trate diet, lack of turnout and lack of so­cial­iza­tion with other horses,” says Wick­ens. “We think horses start crib­bing as a cop­ing mech­a­nism. Re­cent stud­ies have shown that when horses are al­lowed to per­form stereo­typic be­hav­ior, we see a re­duc­tion in the stress hor­mone cor­ti­sol and/or heart rate.”

In a 2016 Swiss study, re­searchers sub­jected 19 crib­bers and 18 non­crib­bing con­trol horses to a se­ries of tests that re­quired them to find a bucket of food in an arena. The crib­bing horses were di­vided into two fur­ther groups: 10 were per­mit­ted to crib dur­ing the tests, and nine were pre­vented from en­gag­ing in the ac­tiv­ity. Anal­y­sis of each horse’s saliva be­fore and af­ter each test showed that cor­ti­sol lev­els were high­est among crib­bing horses who were not per­mit­ted to crib. “Our re­sults sug­gest that crib-bit­ing horses that did not crib-bite dur­ing the learn­ing tests were more stressed than all

The cur­rent think­ing is that an in­di­vid­ual hors might have a ge­netic pre­dis­po­si­tion to crib, but the be­hav­ior isn’t trig­gered un­til he is sub­jected to stres­sors re­lated to his life­style

other horses,” the re­searchers wrote.

“This study sug­gested that crib­bing as a cop­ing mech­a­nism might be a valid the­ory: When the horses were al­lowed to crib they were less stressed,” Wick­ens says. How­ever, she adds, not every study has pro­duced the same re­sults: “Other re­searchers have found no dif­fer­ence at all, and some­times even a re­verse re­la­tion­ship.”

One pos­si­ble ex­pla­na­tion for the dis­crep­an­cies is the method of sam­ple col­lec­tion for mea­sure­ment of cor­ti­sol. “In the past we had to do this through blood col­lec­tion to an­a­lyze plasma cor­ti­sol. Even if the horse is fairly ac­cus­tomed to han­dling and vet­eri­nary care, when you draw blood you are still in­tro­duc­ing some stress just to get the sam­ple,” Wick­ens says. “But now that we have less in­va­sive meth­ods of mea­sur­ing stress hor­mones [such as in saliva or fe­ces] po­ten­tial stress in­duced dur­ing sam­pling is min­i­mized, and the re­sults are of­ten more ro­bust.”

One older the­ory held that horses crib to re­lease en­dor­phins, which pro­duce eu­pho­ria of­ten de­scribed as a “high,” but more re­cent re­search sug­gests that the equa­tion is not that sim­ple. “Now, we don’t nec­es­sar­ily think they are crib­bing to get the high, but per­haps to re­lieve stress. The brain chem­istry and phys­i­ol­ogy of crib­bing horses is al­ready a lit­tle dif­fer­ent or be­comes al­tered, and they tend to be more sen­si­tive. So when they are fed a highly palat­able meal, it tends to stim­u­late plea­sure re­cep­tors in the brain to a de­gree that is height­ened com­pared to a nor­mal horse,” she ex­plains. “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 are re­in­forc­ing the crib­bing, but I don’t think it’s nec­es­sar­ily the crib­bing it­self that is giv­ing the horse the fix.”


Re­searchers are also still work­ing to un­der­stand how crib­bing might af­fect a horse’s health. Horses who crib do seem to be more prone to cer­tain types of colic, al­though the con­nec­tion is un­clear.

“So far the data we have is lim­ited and does not nec­es­sar­ily point to a true cause and ef­fect,” says Wick­ens. “We don’t re­ally know if crib­bing makes horses more prone to colic or if these

There is still much we do not un­der­stand about the re­la­tion­ship be­tween colic and other gas­troin­testi­nal prob­lems and crib­bing in horses

horses al­ready have some un­der­ly­ing di­ges­tive sys­tem dys­func­tion and are prone to colic, and this made them more likely to crib. It’s like the ques­tion about which came first, the chicken or the egg. We don’t re­ally know.”

A horse does lift his rib cage and tighten his di­aphragm and ab­dom­i­nal mus­cu­la­ture when he cribs. “In one study we looked at pres­sure in the ab­domen, and crib­bers have higher pres­sure when they crib, which is not good,” says Mun­ster­man. But the ef­fects of this are not well un­der­stood, she adds: “We were un­able to ac­tu­ally link this with spe­cific dis­eases it might cause, but there might be a cor­re­la­tion. We are still try­ing to fig­ure out if this is some­thing we should pur­sue in fur­ther stud­ies.”

In 2004, re­searchers con­firmed that horses who crib may be more likely to de­velop epi­ploic fora­men en­trap­ment (EFE) a type of colic that oc­curs when a sec­tion of small in­tes­tine be­comes trapped be­tween the liver and the pan­creas. Of 419 horses who were treated for EFE, 47 per­cent were crib­bers--but it is also im­por­tant to note that the ma­jor­ity of the horses in the study, 53 per­cent, de­vel­oped the con­di­tion with no his­tory of crib­bing.

“There is a nat­u­ral hole in the ab­domen, called the epi­ploic fora­men, that every species has, in­clud­ing hu­mans,” says Mun­ster­man. “The think­ing is that this hole widens in crib­bers be­cause of the pres­sure changes, and at some point a loop of small in­tes­tine may slip through, which stran­gu­lates that piece. But to ac­tu­ally see it hap­pen, you’d have to open the ab­domen.”

Un­der­stand­ing the con­nec­tions, if any, be­tween colic and crib­bing will re­quire fur­ther re­search. “A few stud­ies in the vet­eri­nary lit­er­a­ture have demon­strated an as­so­ci­a­tion be­tween colic and crib­bing, but there are many other causes of colic,” says Wick­ens. “Anec­do­tally, I have known many crib­bing horses who have never had prob­lems with colic and many non-crib­bers who have had fre­quent bouts of colic. There is still much we do not un­der­stand about the re­la­tion­ship be­tween colic and other gas­troin­testi­nal prob­lems and crib­bing in horses, and this war­rants fur­ther in­ves­ti­ga­tion.”


The think­ing that crib­bing re­lieves stress is worth con­sid­er­ing when de­cid­ing how best to man­age a horse who en­gages in this be­hav­ior. “My ad­vice is to not try to stop them, be­cause thwart­ing this be­hav­ior may be cruel,” says Mun­ster­man. “We need to learn more about crib­bing be­cause it may be bet­ter for the horse to be able to con­tinue this stress-re­liev­ing ac­tiv­ity, and just fig­ure out a way for him to do it safely.”

Horses who have been crib­bing for many years are un­likely to stop, but it is pos­si­ble that manag­ing a horse to re­duce the stress in his life­style may di­min­ish the be­hav­ior. Here are some things to try:

• Ad­dress any un­der­ly­ing dis­com­fort. Some horses may be­gin crib­bing to re­lieve gas­tric dis­com­fort. “Ab­nor­mal oral be­hav­iors are of­ten as­so­ci­ated with gut dis­com­fort, which may stem from feed­ing man­age­ment. This might be some­thing to try with the horse that’s just be­gun to crib and might be suc­cess­ful in halt­ing it,” says Wick­ens.

“If it’s a younger horse or one that has just started crib­bing, you might want to eval­u­ate the diet,” she adds. “If you catch this be­hav­ior early, be­fore it has be­come well es­tab­lished, you might work with your vet­eri­nar­ian to make sure there’s no gas­troin­testi­nal is­sue. It might be eas­ier to re­di­rect a be­gin­ning crib­ber than a horse that’s

Horses who have been crib­bing for many years are un­likely to stop, but it is pos­si­ble that re­duc­ing the stress in a horse’s life­style may di­min­ish the be­hav­ior.

been do­ing it for sev­eral years.”

Many horses who crib have ul­cers--al­though this is not a de­fin­i­tive cause, since many other horses who have ul­cers do not crib. While work­ing to­ward her PhD, says Wick­ens, “We tested the hy­poth­e­sis that crib­bers have a greater num­ber and/or sever­ity of gas­tric ul­cers [than did horses who do not crib]. When we video-en­do­scoped those horses, we did not find a sig­nif­i­cant dif­fer­ence be­tween the non-crib­bers and the crib­bers in the con­di­tion of their stom­achs.”

Still, it may be worth­while to take steps to re­lieve any po­ten­tial gas­tric dis­com­fort. “Keep­ing [horses who crib] on feeds that help re­duce or pre­vent ul­cers is rec­om­mended,” says Mun­ster­man. One choice would be to of­fer al­falfa hay be­cause it is high in cal­cium and has a buffer­ing ef­fect on stom­ach acid.

• Feed wisely. What­ever other mea­sures you might take, keep­ing hay in front of a horse is a good way to keep his mouth oc­cu­pied. “This is an­other way for the horse to ex­press his oral fix­a­tion, by con­tin­u­ally nib­bling hay,” Wick­ens says. “It may not stop the crib­bing but might re­duce the fre­quency of it.”

If a horse needs to have his calo­ries re­stricted, then a slow feeder---which lim­its the amount of hay a horse can get in one bite---can help to make his ra­tion last longer. Wick­ens sug­gests that tak­ing a more creative ap­proach may also help keep the horse oc­cu­pied: “Rather than just putting some hay out, you might make some ef­fort to en­rich the horse’s for­ag­ing ex­pe­ri­ence. You might place a few flakes in dif­fer­ent ar­eas around the pad­dock so the horse has to move around and mimic for­ag­ing be­hav­ior,” she says.

She also sug­gests of­fer­ing dif­fer­ent types of hay around the turnout. “Some of it could be a lit­tle more nu­tri­tious if it’s a per­for­mance horse or any horse that needs more calo­ries,” she says. “Some legume hay along with the grass hay flakes placed here and there around the pad­dock or pas­ture can make a lit­tle more work and ac­tiv­ity for the horse.” This gives the horse more to do than sim­ply stand­ing at a feeder, eat­ing.

When a horse needs more calo­ries than he can get from for­age alone, Wick­ens rec­om­mends choos­ing feeds with more fat and fiber and less starch and sugar. “In general, this also tends to have a calm­ing ef­fect,” she says. “There are many com­mer­cial feeds that con­tain highly di­gestible fiber sources like beet pulp and al­falfa meal. These can pro­vide more calo­ries and help main­tain body con­di­tion while pro­mot­ing pos­i­tive be­hav­ior and re­duc­ing un­wanted be­hav­iors.”

An­other tac­tic might be to feed hay first, then of­fer grain. “A strat­egy that has met with some suc­cess is to make sure they’ve al­ready had some for­age be­fore be­ing fed a grain meal,” says Wick­ens. “If you leave some hay in the stall at the same time you are giv­ing the grain, it may also help. It won’t stop the crib­bing but may be a man­age­ment tool that could help.”

• Max­i­mize turnout and amenable com­pan­ion­ship. Horses who be­gin crib­bing are of­ten the ones who, at one point in their lives, were con­fined to stalls and trained for per­for­mance ca­reers. Once the habit is in­grained, many horses will con­tinue to crib even when turned out to pas­ture with a herd.

“Some own­ers just don’t have ac­cess to pas­ture for their horses,” Mun­ster­man says. Still, max­i­miz­ing what­ever turnout is avail­able, with amenable com­pan­ions, may help to re­duce the be­hav­ior. “If they are out at pas­ture and do­ing jobs and a mod­er­ate amount of work, there is less time for them to crib,” Mun­ster­man adds. “We are pretty sure the crib­ber isn’t go­ing to teach the oth­ers to crib, so putting him with

What­ever other mea­sures you might take, keep­ing hay in front of a horse is a good way to keep his mouth oc­cu­pied.

May­hew’s Il­lus­trated Horse Man­age­ment, by Ed­ward May­hew, 1860

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