Prob­lems in the Equine Hindgut

Could your horse be suf­fer­ing from colonic ul­cers?

Dressage Today - - Content - By Lil­lian Si­mons

Could your horse be suf­fer­ing from­colonic ul­cers?

You might have no­ticed that you’ve been hear­ing the phrase “hindgut health” in con­ver­sa­tions about horses more so now than ever be­fore. What does “hindgut health” mean in the con­text of your horse and what does it mean for you as his owner?

In this ar­ti­cle, we break down the ba­sics with help from experts Frank An­drews, DVM, LVMA equine com­mit­tee pro­fes­sor and di­rec­tor of the Equine Health Stud­ies Pro­gram at Louisiana State Univer­sity in Ba­ton Rouge, Louisiana, and Christina (“Cricket”) Rus­sillo, DVM, a se­nior as­so­ciate at Vir­ginia Equine Imag­ing in The Plains, Vir­ginia. Re­mem­ber, in ad­di­tion to the in­for­ma­tion pro­vided in this ar­ti­cle, al­ways be sure to con­sult your vet­eri­nar­ian about what is best for your horse as an in­di­vid­ual.

Hindgut Ba­sics

The horse’s hindgut—or large in­tes­tine, which in­cludes the ce­cum and colon—is es­sen­tial to the func­tion of the horse’s over­all di­ges­tive sys­tem and is im­por­tant for bac­te­rial con­tent. When feed is pro­cessed in the horse’s di­ges­tive sys­tem, it is fer­mented and di­gested by bac­te­ria in the hindgut. Fer­men­ta­tion is the chem­i­cal break­down of sub­stances by bac­te­ria, yeast or other micro­organ­isms.

Fer­men­ta­tion pro­vides the horse with en­ergy, vi­ta­mins, min­er­als and amino acids. When the horse suf­fers from poor hindgut health, he lacks these key di­etary com­po­nents. A lack of proper fer­men­ta­tion not only re­sults in a de­crease of these di­etary essen­tials, but also in poor feed uti­liza­tion, poor ap­petite, de­hy­dra­tion, poor coat and hoof con­di­tion, re­duced im­mune func­tion and a change in at­ti­tude. These neg­a­tive ef­fects will ul­ti­mately re­sult in poor per­for­mance and train­ing.

Horses are bi­o­log­i­cally de­signed to con­tin­u­ously con­sume small amounts of food, such as pas­ture grass through­out the day. How­ever, the mod­ern per­for­mance horse of­ten has a life­style that vastly dif­fers from this model of con­tin­u­ous graz­ing. When in­her­ent habits like this are dis­rupted, com­pro­mised or to­tally elim­i­nated and im­prop­erly sub­sti­tuted, then the horse is im­me­di­ately at risk for di­ges­tive is­sues, An­drews says.

Prob­lems in the Hindgut

Horses can ex­pe­ri­ence a wide va­ri­ety of hindgut health is­sues, rang­ing from di­ar­rhea to tor­sion col­ics. How­ever, ac­cord­ing to Rus­sillo, the most com­monly oc­cur­ring hindgut health is­sue in the per­for­mance horse is colonic ul­cers, which are the fo­cus of this ar­ti­cle.

“Colonic ul­cers are the num­ber-one thing I deal with in my pa­tient pop­u­la­tion,” she says. “Other is­sues that can pop up in­clude in­fec­tious causes of di­ar­rhea [such as Po­tomac horse fever], large bac­te­rial shifts in the colon caused by orally ad­min­is­tered an­tibi­otics and di­etary in­tol­er­ances [for ex­am­ple, caused by changes in pas­ture]. But by and large, the thing that we’re day in, day out screen­ing for in the per­for­mance horse is def­i­nitely go­ing to be ‘could this horse have colonic ul­cers?’” Rus­sillo says.

What is a Hindgut Ul­cer?

An ul­cer can be de­fined as a thin­ning of the lin­ing of the gas­troin­testi­nal tract. Ul­cers can oc­cur in the foregut (stom­ach) and are also re­ferred to as gas­tric ul­cers. How­ever, ul­cers can also oc­cur in the hindgut, specif­i­cally in the colon, and are there­fore re­ferred to as colonic ul­cers.

An­drews de­fines a hindgut ul­cer as a de­pres­sion of the lin­ing of the colon. Hindgut ul­cers are dif­fi­cult to di­ag­nose and of­ten re­quire an ul­tra­sound. The sever­ity of the con­di­tion is de­ter­mined by the thick­ness of the colon’s outer wall.

Colonic ul­cers are ex­tremely dif­fi­cult to truly di­ag­nose be­cause it is im­pos­si­ble to thor­oughly ex­am­ine the colon with­out surgery. “Sur­gi­cal di­ag­no­sis of colon ul­cers is the true gold stan­dard, be­cause the sur­geon can ei­ther vi­su­al­ize the ul­cer or per­form a biopsy that can be ex­am­ined mi­cro­scop­i­cally to de­ter­mine the de­gree of ul­cer­a­tion,” Rus­sillo says. While surgery isn’t typ­i­cally rec­om­mended to di­ag­nose ul­cers, it’s more in­dica­tive of just how hard it is to re­ally un­der­stand to what de­gree a horse is af­fected, she ex­plains. “Hence, we uti­lize the com­bi­na­tion of clin­i­cal signs, ul­tra­sound and blood work.”

Gas­tric ul­cers have been a pop­u­lar topic of dis­cus­sion for years, but the con­ver­sa­tion about colonic ul­cers, on the other hand, has re­cently in­creased. Rus- sillo at­tributes this to a greater aware­ness that the prob­lem ex­ists in the first place. “Aware­ness and education are pri­mar­ily why there’s been an in­crease in this dis­cus­sion. We just now know that we need to look for it,” she says.

How Com­mon Are Colonic Ul­cers?

Ul­cers are a com­mon is­sue in per­for­mance horses. Rus­sillo ref­er­ences a study per­formed in 2005 by Franklin L. Pel­le­grini, DVM, that ex­am­ined the pres­ence of colonic ul­cers in horses at necropsy. What could be con­cluded, based on the study, ac­cord­ing to Rus­sillo, is that some­where be­tween 44 and 60 per­cent of horses have some level of colonic ul­cer­a­tion, with a higher per­cent­age in per­for­mance horses. “Stom­ach ul­cers are still more preva­lent,” she says. “But hindgut ul­cers are def­i­nitely a real thing and worth hav­ing con­ver­sa­tions with own­ers about.”

Clin­i­cal Signs

Hindgut ul­cers tend to have more pro­found clin­i­cal signs than gas­tric ul­cers, ac­cord­ing to An­drews. Signs in­clude a re­cur­ring lack of ap­petite, lethargy, in­ter­mit­tent fever, colic bouts, oc­ca­sional edema on the belly from a loss of pro­tein in the blood, weight loss and thin body

con­di­tion. Ac­cord­ing to Rus­sillo, typ­i­cal signs in­clude a com­bi­na­tion of loose ma­nure and large fe­cal balls or, in some cases, com­plete di­ar­rhea. Liq­uid ma­nure down the horse’s in­ner thighs and legs also serves as an in­di­ca­tion.

When An­drews ob­serves a horse with chronic is­sues of colic, di­ar­rhea, lethargy or poor per­for­mance, he says peo­ple tend to think the horse is suf­fer­ing from gas­tric ul­cers. This is a com­mon mis­con­cep­tion. Typ­i­cally, he says, these clin­i­cal signs ac­tu­ally re­late to is­sues in the hindgut, which can­not be seen with an en­do­scope, so ul­tra­sound ex­am­i­na­tion and blood work are much more help­ful. It should be noted that horses with colonic ul­cers might have gas­tric ul­cers as well due to stress, says An­drews.


In order to di­ag­nose colonic ul­cers, vet­eri­nar­i­ans most of­ten per­form a trans­ab­dom­i­nal ul­tra­sound. This in­volves an ul­tra­sound ex­am­i­na­tion of the ab­domen, with a fo­cus on the horse’s right side in an ef­fort to vi­su­al­ize the right dor­sal colon. This, ac­cord­ing to Rus­sillo, re­quires spe­cial­ized equip­ment and skill on the part of the vet­eri­nar­ian in know­ing where to look. Typ­i­cally, the ul­tra­sound is po­si­tioned be­tween the horse’s ribs and di­rected to­ward the colon. The vet­eri­nar­ian then at­tempts to mea­sure the colon’s outer layer, or serosa. How­ever, given the com­plex­ity in di­ag­nos­ing colonic ul­cers, even if the find­ings in­di­cate colonic edema, clin­i­cal signs must be in­cor­po­rated into the di­ag­no­sis as well, Rus­sillo says.

Clues from Blood Work

Hindgut ul­cers can also be de­tected through blood work, which pro­vides in­for­ma­tion, in this case, on the horse’s pro­tein lev­els. First, they will ob­serve a com­plete blood count, look­ing for low pro­tein con­cen­tra­tions in the blood. How­ever, the to­tal pro­tein is typ­i­cally within nor­mal lim­its, so a spe­cific al­bu­min test should be done.

Typ­i­cally, if a horse is suf­fer­ing from hindgut ul­cers, his al­bu­min (the pri­mary pro­tein) con­cen­tra­tion is low. Also, if there is in­flam­ma­tion in the hindgut, there will be a spike in the horse’s glob­u­lin con­cen­tra­tion.

Vet­eri­nar­i­ans also ob­serve a horse’s hemogram, a test mea­sur­ing both white and red blood cell counts. A hemogram de­tects ane­mia and in­fec­tion. Horses with colonic ul­cers will be mildly ane­mic, which means they have a de­fi­ciency in red blood cells, or he­mo­glo­bin, in the blood and will have a high white blood cell count, which de­notes in­fec­tion.

Ac­cord­ing to An­drews, vet­eri­nar­i­ans are now uti­liz­ing a test that de­tects serum amy­loid A (SAA) pro­teins. This test de­ter­mines if the horse is suf­fer­ing from in­flam­ma­tion. An­drews ex­plained that hindgut ul­cers or any ul­cer­a­tive con­di­tion is as­so­ci­ated with in­flam­ma­tion and the re­lease of acute-phase in­flam­ma­tory pro­teins like SAA, which the test is used to de­tect. A high value could in­di­cate hindgut ul­cers and fol­low-up test­ing may show if treat­ment is effective, which would be in­di­cated by a de­crease in the SAA value. The caveat to this kind of test is that an in­crease in SAA is non­spe­cific and any in­flam­ma­tion in the horse’s body can lead to an in­crease in SAA, mean­ing it is not a test that can dif­fer­en­ti­ate stom­ach ul­cers from hindgut ul­cers on its own.

Treat­ment and Pre­ven­tive Mea­sures

In terms of treat­ment mea­sures for the hindgut, An­drews starts by re­duc­ing the amount of bulk in the horse’s diet. He says hay is con­sid­ered a “high-bulk diet,” as it takes up a lot of vol­ume in the large colon, re­quir­ing the colon to work harder to mix it and digest it. It is also scratchy. In­stead, An­drews rec­om­mends pel­leted feeds be­cause the vol­ume of ma­te­ri­als in the hindgut is much smaller and less scratchy. These prod­ucts digest quicker and the resid­ual con­tent is there­fore smaller.

The colon’s job is to pull liq­uid from the horse’s food and ab­sorb the nu­tri­ents back into his sys­tem and then pack­age the waste into ma­nure. If a horse is di­ag­nosed with colonic ul­cers, then it is vi­tal for the colon to be given time to rest. To do this, own­ers must re­duce the horse’s in­take of long-stem fiber, which means elim­i­nat­ing hay in­take. Hay is a lot of work for the colon to digest and process and, in this case, it can scratch and cause ir­ri­ta­tion to the hindgut. In­stead, hay should be sub­sti­tuted with soaked al­falfa cubes, al­falfa pel­lets, beet pulp or a com­plete feed that in­cludes a horse’s nec­es­sary daily dose of fiber.

De­creas­ing a horse’s hay may cause con­cern for some own­ers, as hay is com­monly fed to horses. How­ever, An­drews

Horses are bi­o­log­i­cally de­signed to con­tin­u­ously con­sume small amounts of food, such as pas­ture grass, through­out the day.

Weight loss, thin body con­di­tion and lack of ap­petite are some of the clin­i­cal signs of colonic ul­cers.

$ecauSe cOlONic ul­ceRS aRe diĘcult tO di­ag­NOSe, vet­eRi­NaR­i­aNS Rely ON a cOM­bi­Na­tiON Of cliN­i­cal SigNS, ul­tRa­SOuNd aNd blOOd VORL.

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