Gastrointestinal issues (GI) are the number one cause of morbidity in horses other than old age. An unhealthy digestive system can cause poor performance, pain, discomfort, diarrhea, and a whole host of issues that can sideline your horse.
Horse rolling on the ground during a colic bout.
The gastrointestinal track of a horse is extremely large, and there are many things that can cause disturbances to the normal functioning or health of the gut.
© 2017 by Anastasija Popova New window.
It’s no wonder researchers are paying close attention to the ‘second brain’ and it’s billions of inhabitants. Ontario Veterinary College (OVC) researcher, Dr. Luis Arroyo has been studying the equine gastrointestinal systems for many years with several research projects receiving funding from Equine Guelph. Arroyo discusses what we know about equine gut health, causes of GI disorders and the extensive 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 disturbances to the normal functioning or health of the gut.” A healthy gut microbiome is essential for the horse’s entire body to function optimally.
Signs of GI issues
Common signs of disorders could include abdominal pain, bloating, changes in fecal consistency (including diarrhea or constipation), excessive drooling, decrease in water consumption, lack of or poor appetite, weight loss and low body condition score.
Changes of behaviour such as becoming cranky or moody can be tell-tale signs there is unrest in the GI system. 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 suddenly decline, if there is no obvious lameness, GI issues are high among the considerations.
“Horses are herbivores, designed to consume a diet of forage, and to break down complex sugars within that forage.” says Arroyo. “The gut microbiota does this job and is very important for healthy digestion.” Recent research is connecting the changes in diversity of microbial communities to conditions like colic, colitis, and gastric ulcers.
Causes of GI Issues
Colic is the number one clinical condition occurring in horses. It is well-known that sudden dietary changes can be a major contributor 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 development 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 period needs to be considered when making feed changes and this goes for both changes to forage or concentrates.
A table of feed transition periods on the Equine Guelph website states an adaptation period of at least 10 – 14 days is recommended. Transition periods under seven days can increase colic risk over 22 times! (https://www.equineguelph.ca/pdf/tools/How%20to%20Transition%20Feedstuff.pdf)
“Decrease in water 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 impaction colic. Parasite burden can also cause colic. If your horse lives in a sandy environment, like California, ingesting sand can cause impaction colic.
Non-steroidal anti-inflammatory drugs (NSAIDS) can cause colic or ulcers. NSAIDS can interfere with blood supply to the GI tract causing ulceration, for example in the mucosa of the stomach. Prolonged use can cause quite severe ulceration.
NSAIDS are not the only drugs that can contribute to GI issues. “Antibiotics as the name says, kills many kinds of bacteria,” says Arroyo. “They are designed for that! Invariably they deplete some bacterial populations including in the intestine, and that is a problem because that may allow some other bacteria, potentially pathogenic or harmful, to overgrow, and that can cause dysbiosis.”
In a recent study, by 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 antibiotics to horses. Damage to the intestinal microbiota resembled dysbiosis that can potentially result in intestinal inflammation and colitis predisposing the horse to diarrhea. Judicious use of antibiotics and antimicrobials are advised.
There are infectious and non-infectious causes of colitis. Infectious examples include salmonella and then there is Neorickettsia risticii, which if ingested from contaminated sources, can cause Salmonellosis or Potomac horse fever, respectively.
Top Tips to Protect Digestive Health
1. Horses are hind gut fermenters who rely on adequate 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 microbiota and can also be a source of risk for developing 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 continuous-grazers, and they need to have small amounts of feed working through their digestive system to keep it functioning optimally.
5. Have a parasite prevention 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 dental appointments.
8. Motion is lotion – turn out and exercise are extremely important to gut function.
To view the complete article "A Stable Gut: The Key to a Healthy Equine" click HERE .
Press release by The Horse Portal - Cover story by: Jackie Bellamy-Zions