EQUUS - - Medical Front -

A new study from Switzer­land chal­lenges the no­tion that horses who crib are less ca­pa­ble of learn­ing than are their peers.

Crib­bing is clas­si­fied as a stereo­typy--- a repet­i­tive pat­tern of be­hav­ior with no ap­par­ent goal or pur­pose. A crib­bing horse re­peat­edly grasps a solid ob­ject with his teeth, pulls back and gulps air, of­ten emit­ting a dis­tinc­tive grunt­ing sound. Crib­bing has been linked to frus­tra­tion and stress as­so­ci­ated with restrictiv­e en­vi­ron­ments, but once es­tab­lished as a habit, crib­bing of­ten con­tin­ues even when a horse’s man­age­ment changes.

Prior re­search has sug­gested that horses who crib are less “cog­ni­tively flex­i­ble” than their peers. “Crib biters have been shown to have al­tered learn­ing abil­i­ties,” ex­plains Sab­rina Briefer Frey­mond, a doc­toral stu­dent at Agro­scope, the re­search in­sti­tu­tion of the Swiss Na­tional Stud in Avenches. “This means that they might learn some tasks bet­ter and not be able to learn other tasks.” The pre­vail­ing ex­pla­na­tion for this dis­par­ity is that the pro­longed stress that drives a horse to crib also al­ters the basal gan­glia of his brain, lead­ing to a change in cog­ni­tive func­tion.

“This basal gan­glia is thought to be af­fected by stereo­typy per­for­mance or to be the cause of devel­op­ment of stereo­typy,” says Frey­mond. “The hy­poth­e­sis of the devel­op­ment of stereo­typ­ies in cap­tive an­i­mals is that they ap­pear after repet­i­tive frus­tra­tion or stress due to the re­stric­tion of species-spe­cific mo­ti­va­tions or need. If such a frus­tra­tion-in­duc­ing sit­u­a­tion re­peats it­self, over time it may change or al­ter some part of the basal gan­glia and then de­velop into stereo­typic be­hav­iors.”

She adds that pre­vi­ous stud­ies showed that crib­bers sus­tained some al­ter­ation in the basal gan­glia and they have dif­fi­cul­ties with so-called ex­tinc­tion tasks, which are tests that chal­lenge ex­ist­ing be­hav­ior. For

in­stance, Frey­mond says, “in such a task, horses learn that food is in one place, and after a while there is sud­denly no more food in this place. Crib biters have been shown to go more of­ten to see if there was in­deed no more food, show­ing that they were hy­per-mo­ti­vated to go to a place with a re­ward com­pared to non-stereo­typic horses. [Crib biters] are also thought to be un­able to break habits after over­train­ing, be­ing trained with many tri­als for the same thing.”

To in­ves­ti­gate this fur­ther, Frey­mond and her col­leagues de­vised a study based on six crib­bers and seven con­trol horses who did not crib. The re­searchers built a wooden box that held two feed bowls, each ac­ces­si­ble only if the horse used his nose to push through a flap in front of it. In the ha­bit­u­a­tion phase be­fore the study be­gan, the horses were taught to open two plain flaps (right or left) with their noses.

Then all the horses were ex­posed to four learn­ing tasks: first and sec­ond ac­qui­si­tion and their cor­re­spond­ing re­ver­sals. For the first por­tion of the study, the two flaps were af­fixed with sym­bols bear­ing ei­ther a black cross on a white back­ground or a white cross on a black back­ground (ran­domly on the two sides) and a bowl of feed was placed be­hind the two flaps. The horse then had to choose one flap. If he chose cor­rectly, he was re­warded with the grain treat be­hind the flap. If the horse chose wrong, he re­ceived no re­ward, be­cause the cor­re­spond­ing flap was blocked. Once the horse had learned this process well enough to make six con­sec­u­tive cor­rect choices, the col­ors of the “cor­rect” door were re­versed. When the horses learned that task, the shapes were changed, with a black cir­cle or a white cir­cle on a con­trast­ing back­ground. Fi­nally, when the horse had learned that task, those col­ors were again re­versed.

All ses­sions were recorded on video and the re­searchers re­viewed the footage to score how quickly each horse learned each task. And, as the horses learned the tasks, phys­i­o­log­i­cal mea­sure­ments such as heart rate and in­ter-beat in­ter­vals---a mea­sure of phys­i­o­log­i­cal stress--were taken via a car­diac mon­i­tor.

The data showed that while the crib­bers re­quired more ses­sions to learn to open the flaps dur­ing the pre-study/ha­bit­u­a­tion phase, there was no dif­fer­ence be­tween the groups in per­form­ing the dis­crim­i­na­tion tasks---learn­ing the flap with the “cor­rect” sym­bol fixed on it. Nor was there a sig­nif­i­cant dif­fer­ence in how quickly the groups “un­learned” the task once the sym­bols or col­ors were switched.

Al­though there is still much to be learned, the re­searchers say that man­age­ment ap­proaches to re­duce stress in crib­bing horses can en­hance their re­sponse to train­ing ef­forts.

“With this new study, we demon­strate that crib biters can man­age a very com­plex task [re­ver­sal learn­ing based only on vis­ual cue],” says Frey­mond. “It means that they are able to change some­thing that has been pre­vi­ously learned. How­ever, it is im­por­tant to state that they needed a longer time to be ha­bit­u­ated to the ex­per­i­ment than the con­trol group.

“This was the first time that crib biters and con­trol horses were com­pared in a re­ver­sal learn­ing task,” says Frey­mond. “The best ex­pla­na­tion [for our find­ings] is that crib biters might have al­ter­ation in the re­ward area of the brain, how­ever, not in the area that con­trols re­ver­sal learn­ing. This is con­firmed by the fact that crib bit­ing horses needed a longer time to be ac­cli­mated dur­ing the study.”

Al­though there is still much to be learned, Frey­mond says man­age­ment ap­proaches that re­duce stress in crib­bing horses can en­hance their re­sponse to train­ing ef­forts.

“In or­der to min­i­mize stress for horses with stereo­typ­ies, it is cru­cial to of­fer them ac­cess to hay and pos­si­bly straw to sat­isfy their need to chew, al­low them so­cial con­tact with other horses and ed­u­cate them with good train­ers, giv­ing aids with per­fect tim­ing,” she says. “Un­der these cir­cum­stances, these horses could be even ‘bet­ter’ than horses who don’t crib.”

Ref­er­ence: “Stereo­typic horses (Equus ca­bal­lus) are not cog­ni­tively im­paired,” Animal Cognition, Jan­uary 2019.

IN TRAIN­ING: A new study sug­gests that horses who crib are just as ca­pa­ble of learn­ing new tasks as are their peers.

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