34/ APRIL 2024 THE RIDER A Stable Gut: The Key to a Healthy Equine Gastrointestinal issues


(GI) are the number one cause of morbidity in horses other than old age. An un- healthy digestive system can cause poor performance, pain, discomfort, diarrhea, and a whole host of issues that can sideline your horse. It’s no wonder researchers are paying close attention to the ‘second brain’ and it’s billions of inhabitants. On- tario Veterinary College (OVC) researcher, Dr. Luis Arroyo has been studying the equine gastrointestinal systems for many years with several research projects re- ceiving funding from Equine Guelph. Arroyo dis- cusses what we know about equine gut health, causes of GI disorders and the exten- sive continuing research to understand what unstable and stable gut populations look like. Starting with some


basic anatomy Arroyo says, “The gastrointestinal track of a horse is extremely large, and there are many things that can cause distur- bances to the normal func- tioning or health of the gut.” A healthy gut microbiome is essential for the horse’s en- tire body to function opti- mally.


Signs of GI issues Common signs of dis-


orders could include abdom- inal pain, bloating, changes in fecal consistency (includ- ing diarrhea or constipa- tion), excessive drooling, decrease in water consump- tion, lack of or poor ap- petite, weight loss and low body condition score. “Some cases are more


obvious to owners,” says Arroyo, “like poor perform- ance, or acute or chronic di- arrhea.” Changes of behaviour


such as becoming cranky or moody can be tell-tale signs there is unrest in the GI sys- tem. Biting at the flanks can signal abdominal pain as


well as reactivity to being saddled. When the horse stops wanting to perform and athletic abilities sud- denly decline, if there is no obvious lameness, GI issues are high among the consid- erations. “Horses are herbi-


vores, designed to consume a diet of forage, and to break down complex sugars within that forage.” says Ar- royo. “The gut microbiota does this job and is very im- portant for healthy diges- tion.” Recent research is connecting the changes in diversity of microbial com- munities to conditions like colic, colitis, and gastric ul- cers.


Causes of GI Issues Colic is the number


one clinical condition occur- ring in horses. It is well- known that sudden dietary changes can be a major con- tributor as well as diets that are high in grain. This can create changes in the volatile fatty acids produced in the GI system, which in turn can lead to the develop- ment of gas colic. Arroyo provides the example of switching from dry hay fed in the winter, to rich, lush, spring grass as a big cause of rapid fermentation that can cause colic. Any abrupt change,


even if it’s a good quality feed to a different good quality feed, can be a source of colic. Then there is the more obvious consumption of moldy, poor, quality hay. So not only the quality but the transition/adaptation pe- riod needs to be considered when making feed changes and this goes for both changes to forage or con- centrates. A table of feed transi-


tion periods on the Equine Guelph website states an adaptation period of at least 10 – 14 days is recom- mended. Transition periods under seven days can in-


For example, a biomarker can be used to see how well the body might respond to a treatment or to a disease condition.” “The objective of a


dysbiosis index is quantify- ing ‘X’ number of certain bacteria that are important to us,” says Arroyo. In this case, the dysbiosis derives from sequencing of the bac- terial population in fecal samples. Changes in the intes-


Dr. Luis Arroyo discusses Equine GI health and latest research. YouTube video inter- view with Dr Arroyo on Equine Gut health: https://youtu.be/yN0TS-isezI


crease colic risk over 22 times!


4a4UGCM “Decrease in water


flammatory


consumption can be an issue, especially in countries with seasons,” says Arroyo. When water gets really cold, horses often drink less, and if it freezes, they don’t drink at all, which can lead to im- paction colic. Parasite bur- den can also cause colic. If your horse lives in a sandy environment, like Califor- nia, ingesting sand can cause impaction colic. Non-steroidal anti-in- drugs


(NSAIDS) can cause colic or ulcers. NSAIDS can in- terfere with blood supply to the GI tract causing ulcera- tion, for example in the mu- cosa of


the stomach.


Prolonged use can cause quite severe ulceration. NSAIDS are not the


only drugs that can con- tribute to GI issues. “Antibi- otics as the name says, kills many kinds of bacteria,” says Arroyo. “They are de- signed for that! Invariably they deplete some bacterial populations including in the intestine, and that is a prob- lem because that may allow some other bacteria, poten- tially pathogenic or harmful, to overgrow, and that can cause dysbiosis.” In a recent study, by


https://bit.ly/


fellow OVC researcher, Dr. Gomez and co-workers, it was determined that damage to the intestinal microbiota could occur after only 5 days of administering an- tibiotics to horses. Damage to the intestinal microbiota resembled dysbiosis that can potentially result in intes- tinal inflammation and coli- tis predisposing the horse to diarrhea. Judicious use of antibiotics and antimicro- bials are advised. There are infectious


and non-infectious causes of colitis. Infectious examples include salmonella and then there is Neorickettsia ris- ticii, which if ingested from contaminated sources, can cause Salmonellosis or Po- tomac horse fever, respec- tively. “Any stress factors


such as transportation, fast- ing or intense exercise like racing, can be a factor for developing stomach ulcers,” says Arroyo.


Current Diagnostics Putting together a pic-


ture of the horse’s health status includes gathering clinical history from the horse owner and performing a physical examination for motility and hydration sta- tus. A biochemistry profile and complete set count can be gathered from blood test- ing.


Gastric ultrasound al-


lows veterinarians to view the wall of the intestine, not- ing if it has thickened or dis- tended, which could occur in cases when there is colic. They can assess appearance and find out if the intestine is displaced or if there is a twist. Gastroscopy is com- monly used to find ulcers in the stomach and can reach as far as the first part of the duodenum.


GI Research “DNA sequencing has


been a breakthrough in sci- ence in terms of understand- ing the communities of different microorganisms living in many different niches from the skin to the lungs to the upper airways to the intestine,” says Ar- royo.


It has allowed in-depth study of the population of


microorganisms, providing a big picture of the different inhabitants in various areas of the GI tract, such as the lumen of the small intestine and the small and large colon. “The microorganisms vary, and they have different functions in each compart- ment,” says Arroyo. DNA sequencing has


allowed researchers to study microbial populations and gather information on what happens to bacterial com- munities when impacted by diseases like colitis. “We can see who is down, and who is up,” explains Arroyo, “and determine what popu- lations have been depleted.” It has led to a better knowl- edge of which of the billions of factors are harmful to the system and which can com- promise the health of the horse.


Robo-gut is one exam-


ple of a fantastic system where bacterial communi- ties are being replicated in the lab to mimic what would be found in a natural envi- ronment. Researchers at the Uni-


versity of Guelph have measured metabolic profiles of the bacterial population after the addition of supple- ments like probiotics and prebiotics. They found they can dramatically change the metabolites that are being produced, according to what is being added to the sys- tem.


Exciting new research


that could impact the future of diagnostics includes screening for biomarkers as indicators of


health among equine micro- biota. Dr. Arroyo is cur- rently working with research partner, Dr. Marcio Costa, from the University of Montreal, looking for biomarkers that indicate changes in the inhabitants of the equine gut that take place during the early onset of illness. “A biomarker is a bio-


logical molecule that you can find in different places,” explains Arroyo. “For ex- ample, you might find them in tissue, blood, urine, or different body fluids. They can signal normal or abnor- mal processes or could re- veal a marker of a disease.


intestinal


tinal microbiota (dysbiosis) are present before and dur- ing the outset of diseases and after treatment with an- tibiotics. Arroyo cites the example of decreased Lach- nospiraceae commonly ob- served when there is intestinal inflammation. Bacterial biomarkers


are currently being used in other species to accurately predict intestinal dysbiosis, for example in cats and dogs. One canine study quantified the number of seven different taxa of im- portance of the total bacter- ial


populations. This


information is entered into a mathematical algorithm that comes up with results ex- plaining which bacteria have increased or decreased. Based on those numbers, one can use a more specific taxa to identify dysbiosis. In a feline study, it was discov- ered that six bacterial taxa could be accurately used to predict diarrhea in 83% of cases. It is hoped the same re-


sults could be accomplished for horses. Developing PCR testing to screen for bio- markers could be a game changer that could poten- tially provide speedy, eco- nomical early diagnostics and early treatment. So far, the most re-


markable finding in the pre- liminary data reveals that in horses with colitis,


the


whole bacterial population is very depleted. “At this stage we are in


the process of increasing our numbers to find significant differences in which bacter- ial taxa are more important,” says Arroyo. “Soon we hope to share which bacteria taxa are more promising for pre- dicting dysbiosis in horses with gastrointestinal dis- ease.”


The researchers are


delving into a huge biobank of samples to identify poten- tial markers of intestinal dysbiosis in horses, utilizing PCR testing as a faster and more economical alternative to the complex DNA se- quencing technologies that have been used to character- ize changes in microbiota thus far. The goal is to de- velop simple and reliable testing that veterinarians can take right to the barn that will result in early treatment and allow closer monitoring of horses at the first onset of GI disease.


Story by: Jackie Bellamy- Zions, Equine Guelph


Web Link(s): Equine Guelph Research A n n u a l https://bit.ly/4a7pmDy


Colic Risk Rater: https://thehorseportal.ca/hea lthcare-tools/colic-tool/


Gut Health online course: https://thehorseportal.ca/cou rses/


Feed transition period c


h a r t https://bit.ly/4a4UGCM : :


Top Tips to Protect Diges- tive Health


1. Horses are hind gut fer- menters who rely on ade- quate amounts of fiber in the diet to maintain health gut function. 2. Make dietary changes slowly as abrupt changes disrupt the microbiota. 3. Avoid large grain meals as huge portions of highly fermentable diets can be quite harmful to the micro- biota and can also be a source of risk for develop- ing gastric ulcers. Opt to spread out concentrates into several smaller rations. 4. Prevent long periods of fasting which can also lead to ulcers. Horses are contin- uous-grazers, and they need to have small amounts of feed working through their digestive system to keep it functioning optimally. 5. Have a parasite preven- tion program. 6. Provide fresh water 24/7 to maintain good hydration and keep contents moving smoothly through the GI tract. 7. Keep up to date on den- tal appointments. 8. Motion is lotion – turn out and exercise are ex- tremely important to gut function. In closing, Arroyo


states, “These top tips will help keep the horse happy and the gastrointestinal tract functioning properly.”


more? Visit


Interested in learning Equine


Guelph’s Free Colic Risk Rater healthcare tool and sign up for short online courses on Gut Health and Colic and Ulcer Prevention at TheHorsePortal.ca


About Equine Guelph: Equine Guelph is the


horse owners’ and care givers’ Centre at the Univer- sity of Guelph in Canada. It is a unique partnership ded- icated to the health and well-being of horses, sup- ported and overseen by equine industry groups. Equine Guelph is the epi- centre for academia, indus- try and government - for the good of the equine industry as a whole. For further in- formation,


visit www.equineguelph.ca.


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