MED­I­CAL FRONT

EQUUS - - Contents - By Chris­tine Barakat and Mick McCluskey, BVSc, MACVSc

• Do color per­cep­tions af­fect

jumping per­for­mance? • Lu­nar cy­cles and breed­ing:

An old wives’ tale de­bunked • Ge­netic test­ing aids

HERDA di­ag­no­sis • Dig­i­tal ra­di­og­ra­phy use­ful

for de­tect­ing enterolith­s • Large in­tes­tine im­pactions stud­ied

The color of the rails on a jump can have an im­pact beyond aes­thet­ics. A new study from Bel­gium shows that horses are more likely to knock over rails of a cer­tain hue.

Work­ing at an in­de­pen­dent company, the Catholic Univer­sity of Leu­ven and Ghent Univer­sity, re­searchers set out to de­ter­mine whether color per­cep­tion in­flu­ences a horse’s jumping per­for­mance. “Horses have the abil­ity to see col­ors as a red–green col­or­blind hu­man does,” says Jan Spaas, PhD, DVM. “They see col­ors but have dif­fi­cul­ties dis­tin­guish­ing them from other col­ors within a small spec­trum range.”

The study was based on an in­door ex­per­i­ment (white ground sur­face), us­ing 20 young show jumpers pi­loted by two rid­ers with in­ter­na­tional com­pe­ti­tion ex­pe­ri­ence, and on an out­door ex­per­i­ment (green ground sur­face) us­ing eight horses. Each horse was rid­den six times over a course of six fences---three blue and three green in al­ter­nat­ing suc­ces­sion. The re­searchers noted which jumps were touched by the horses and which had rails knocked down.

The study was de­signed to elim­i­nate all in­flu­ences other than the color of the fences. For in­stance, be­tween each round the or­der of the col­ored jumps was changed to en­sure that a par­tic­u­lar jump’s po­si­tion would not be a fac­tor in per­for­mance. “The rid­ers were from a very high pro­fes­sional level and [ground lines] were placed at a per­fect dis­tance from the fence,” says Spaas, “so there were no prob­lems in po­si­tion­ing the horse cor­rectly at the fence, re­gard­less of the color.”

The data showed that blue rails jumped in­doors were the most likely to be touched or knocked down by the horses. How­ever, when the cour­ses were jumped out­doors in a grass arena, the dif­fer­ence be­tween the col­ors be­came in­signif­i­cant, “be­cause the blue were less hit and the green a lit­tle bit more than in the first ex­per­i­ment,” says Spaas.

Th­ese find­ings seemed sur­pris­ing at first, says Spaas, but make sense from an evo­lu­tion­ary stand­point: “From a horse’s point of view, I ex­pected more er­rors on green bars in both are­nas and def­i­nitely on the green grass. How­ever, it has been pos­tu­lated that dichro­matic vi­sion [color­blind­ness] is su­pe­rior to trichro­matic vi­sion [nor­mal color vi­sion] at de­tect­ing cam­ou­flage when there is a color match be­tween the tar­get and the back­ground. So, through evo­lu­tion, horses have been trained to see the same col­ored ob­jects as the back­ground. Just imag­ine what preda­tors could do when horses wouldn’t no­tice them in a sim­i­lar back­ground or if they would harm them­selves each time they would have to jump a na­ture-col­ored ob­sta­cle. I re­ally be­lieve it is an evo­lu­tion­ary fea­ture.”

Spaas stresses that this study doesn’t mean horses can’t see blue, rather that they “just don’t jump it that well on a white sur­face. They will be able to dis­tin­guish a blue bucket from a yel­low one, for ex­am­ple.” He adds that rid­ers may want to train over blue-col­ored fences to have an ad­van­tage at com­pe­ti­tions. “On the other hand, clever course de­sign­ers could strate­gi­cally use the color blue in or­der to have fewer clear rounds on white sur­faces.”

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