Health Up­date

Practical Horseman - - Contents -

What af­fects heart health in event horses; ther­a­peu­tic rid­ing and equine wel­fare

In both horses and hu­mans, the au­to­nomic ner­vous sys­tem is largely re­spon­si­ble for things we take for granted—reg­u­lat­ing our car­dio­vas­cu­lar, gas­troin­testi­nal and other sys­tems with­out our con­scious in­volve­ment. There are sym­pa­thetic and parasym­pa­thetic as­pects of the au­to­nomic sys­tem. The for­mer is con­nected with a fight-or-flight re­sponse, while the lat­ter is re­lated to a “rest-and-digest” mode, ex­plains Olivia Lorello, VMD, CVA, from the Swiss In­sti­tute of Equine Medicine at the Univer­sity of Bern.

The two sides are meant to bal­ance out. “When one is high, the other is low,” says Dr. Lorello. A chronic im­bal­ance is a strong in­di­ca­tor of po­ten­tial heart trou­ble. And that makes it an in­ter­est­ing area of study for the event­ing world, which has been haunted in re­cent years by a num­ber of heart-re­lated equine fa­tal­i­ties.

Dr. Lorello and her col­leagues wanted to be­gin defin­ing nor­mal val­ues of au­to­nomic tone mark­ers and how they change over a com­pe­ti­tion sea­son—some­thing that to date has been in­com­pletely de­scribed in event horses.

The team gath­ered two groups of warm­bloods, all ap­prox­i­mately the same age. The con­trol group con­sisted of eight non­com­pet­ing horses and the test group con­sisted of 17 even­ters com­pet­ing at Pre­lim­i­nary through CCI*** lev­els. Not all horses com­pleted the study for ei­ther rider-re­lated or horse health-re­lated rea­sons.

The re­searchers de­fined three stages of the com­pe­ti­tion year: pre­sea­son, mid­sea­son and peak or end of sea­son. At each of these stages, they mea­sured com­mon mark­ers of au­to­nomic tone, in­clud­ing heart-rate vari­abil­ity, blood pres­sure, pre- and post-ex­er­cise cor­ti­sol and mus­cle-en­zyme ac­tiv­i­ties. They also in­cor­po­rated stan­dard­ized ex­er­cise tests (SETs), where the horses were gal­loped in three sets for 1,490 me­ters at in­creas­ing speeds with five-minute trot breaks be­tween sets.

“Blood sam­ples were drawn after each gal­lop,” says Dr. Lorello. “The horses had con­tin­u­ous elec­tro­car­dio­gram mon­i­tor­ing through­out the rid­ing test to mea­sure heart rate and rhythm. This de­vice also had a GPS tracker to mon­i­tor speed.”

Re­searchers found that the even­ters in the test group had lower heart-rate vari­abil­ity than the con­trols, sug­gest­ing that the event horses were main­tain­ing au­to­nomic tone bal­ance. Sim­i­larly, post-ex­er­cise cor­ti­sol was lower in the test group than the con­trol group at mid-sea­son and peak sea­son. This in­di­cates that the even­ters had a lower stress re­sponse to the SETs than the con­trol horses. Not sur­pris­ingly, even­ters also demon­strated higher fit­ness lev­els dur­ing the SETs.

Dr. Lorello states that these re­sults don’t yet lead to a spe­cific con­clu­sion re­gard­ing event horse heart health. But, she notes, “This study serves to bring us one step closer to un­der­stand­ing the po­ten­tial ef­fects of train­ing [and] ex­er­cise on equine ath­letes.” And the more we know, the more we can work to­ward cre­at­ing an en­vi­ron­ment of op­ti­mal well-be­ing for our horses.

Ther­a­peu­tic Rid­ing and Equine Wel­fare

We know that horses can have ther­a­peu­tic ef­fects on hu­mans in nu­mer­ous ways. But how does ther­a­peu­tic rid­ing affect the horse’s wel­fare? Is it a healthy oc­cu­pa­tion for our equine friends? A group with the Univer­sity of Mis­souri-Columbia Col­lege of Vet­eri­nary Medicine Re­search Cen­ter for Hu­man-An­i­mal In­ter­ac­tion wanted to find out.

The team, led by the cen­ter’s di­rec­tor, Re­becca A. John­son, PhD, RN, FAAN, FNAP, pig­gy­backed this study onto work it was al­ready do­ing with mil­i­tary veter­ans. The veter­ans suf­fer from post-trau­matic stress disor­der (PTSD) and were par­tic­i­pat­ing in a ther­a­peu­tic rid­ing pro­gram at the Clear Creek Ther­a­peu­tic Rid­ing Cen­ter. (See the Au­gust 2016 “Health Up­date” or go to www.Prac­ti­calHorse­

Five horses were in­cluded in the study, which was bro­ken into two six-week ses­sions. In Ses­sion 1, the horses were rid­den by the veter­ans. In Ses­sion 2, they were rid­den by ex­pe­ri­enced eques­tri­ans. Dr. John­son and her col­leagues mea­sured the horses’ phys­i­o­log­i­cal stress in­di­ca­tors, in­clud­ing plasma adreno­cor­ti­cotropic

hor­mone, glu­cose, cor­ti­sol lev­els and be­hav­ioral biomark­ers. In each ses­sion, blood was drawn at mul­ti­ple in­ter­vals: on a rest­ing day; be­fore rid­ing on Weeks 1, 3 and 6; after tack­ing up; and after each rid­ing class. Be­hav­ioral biomark­ers were eval­u­ated be­fore each blood draw.

The re­searchers found that when the veter­ans were in the sad­dle, the ther­apy horses’ cor­ti­sol lev­els were higher be­fore and after rid­ing than on the rest­ing day, while it was just the op­po­site with the ex­pe­ri­enced eques­tri­ans. Glu­cose lev­els, on the other hand, ac­tu­ally dropped after the veter­ans rode, com­pared to the rest­ing day.

Over­all, both cor­ti­sol and glu­cose lev­els tended to be higher with the veter­ans than with the ex­pe­ri­enced rid­ers. How­ever, the horses’ stress be­hav­ior scores were sig­nif­i­cantly lower with veter­ans ver­sus ex­pe­ri­ence rid­ers.

Although the re­sults were mixed, the re­searchers noted that all stress in­di­ca­tors re­mained within nor­mal ranges for both groups. They con­cluded that car­ry­ing rid­ers with a dis­abil­ity does not stress the horses or neg­a­tively im­pact their wel­fare—which sets up a win–win–win sit­u­a­tion for the rid­ers, the horses and the ther­apy pro­grams.– Sushil Du­lai Wen­holz

Re­searchers are tak­ing a deeper look into the au­to­nomic ner­vous sys­tem in event horses.

Stud­ies have shown that ther­apy horses do not seem to have el­e­vated stress lev­els dur­ing ses­sions with dis­abled rid­ers or mil­i­tary veter­ans with PTSD.

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