Veterinarians will tell you that when certain types of weather are forecast, they can expect a rise in colic cases. Some correlation between weather and colic is easily understandable. Frozen water supplies in winter and a combination of drought and increased sweating in summer may prevent a horse from drinking as much water as it needs, leading to impaction colic. In other cases, sudden management changes to cope with changes in weather can be to blame.
British researchers recently investigated seasonal patterns of increased risk for colic, which focused on how changes in the weather impact the composition of the horse's gut microbiota, the colony of good and bad bacteria that lives in the horse's digestive tract.
The small study sampled feces from the same seven horses at pasture every two weeks for a year. During this time, the researchers made minimal changes in management. They concluded: “Season, supplementary forage and ambient weather conditions were significantly associated with change in the faecal microbiota composition.”
The data gleaned from the study will be used to establish a baseline for further research to determine if (and what) changes in the microbiota occur in a horse with colic.
Dr. Scott Weese, an internal medicine specialist at the University of Guelph, has completed more than 300 studies of the horse's gastrointestinal system since 1999.
“There's just that one study [that] shows the microbiota can vary over time, but not what drives it or impacts the horse,” said Weese. “It would make sense that changes in the microbiota could be influenced by weather, but that could be from changes in diet, changes in activity, changes in management that occur during different times and a variety of other things, meaning the actual impact of weather is pretty much impossible to say at this point … We know so little about the microbiota (and what we do know is often over-interpreted) so it's hard to have confidence in many conclusions at this time.”
Dr. Nathan Slovis, director of the McGee Medicine Center at Hagyard Equine Medical Institute in Lexington, is one of those veterinarians who has seen a link between weather and colic, particularly falling barometric pressure and gas colic, a relatively minor form of colic. When the wind blows moist air and/or warm air into an area, the barometric pressure drops. A rapid drop in the barometer typically portends rain, or worse.
“When barometric pressure drops, some horses that are a little more prone to colic, you can almost guarantee that they'll colic,” Slovis said.
While there is no published research on the phenomenon, Slovis said it is basic physics and the laws of gas.
“When the barometric pressure drops, according to the laws of gas, it can expand in the intestinal tract,” he said. “So some horses get a little gas colic. And if you're at a high barometric pressure, it shrinks the gas. It definitely can happen … Nobody has done studies in horses and can say absolutely, but it does make sense.”
Changes in barometric pressure that happen over a two- or three-day period are not the problem. Sudden, drastic changes that cause bad weather are the signs that owners with colicky horses should heed.
“That's why people will say, 'My horse always colics when there's bad weather,'” Slovis said. “One day you're 50 degrees and later that evening you're at 10 degrees—those are significant changes in the weather patterns that affect barometric pressure.”
Gas colic happens in humans when they eat certain foods that produce a lot of gas, which causes pain when their intestines distend to accommodate it. In horses, a mild case of gas colic usually will resolve with administration of an analgesic and hand-walking, unless complications arise. Handwalking encourages the gas to move through the horse's intestines and be passed out.
Always contact your veterinarian if your horse colics to get advice on how to handle the particular type of colic it is experiencing.
Slovis said there is no way to prevent bad-weather colic, but a few common-sense changes in diet prior to the drop in barometric pressure may help, such as backing off on alfalfa and cereal grains.
“You might not give them as much of a gas-producing food, like alfalfa, or you might want to back off their grain by a quarter of the amount—things like that that can cause increased fermentation,” he said.
Slovis added that some people with horses prone to bad-weather colic pre-medicate them with Banamine (flunixin meglumine) as a precaution.
“Some people do that, but I'm not saying you have to do that,” he said.
Important Topic for Study
Dr. David Freeman, director of the University of Florida's Island Whirl Equine Colic Research Laboratory, said he's not a believer in the link between weather and colic, other than management changes that might bring on colic. He explained that the types of colic cases he sees at Island Whirl are those that require aggressive hospital treatment or surgery, so he doesn't see the types of colic that local veterinarians typically do.
“[Local veterinarians] see every colic and every type of colic,” he said. “I'd have to respect their opinion. So if they say they see a specific type of weather change, then my first comment would be that we need to somehow document it. It can't be just anecdotal.
“My general stance has been that it's an observation we've heard about for years, but it needs to be documented over periods of time and under different weather conditions, and so forth. Then I think it would take on greater meaning.
“I think it is an important topic,” Freeman continued. “We need to have some good documentation, then we can maybe relate the type of weather to the type of colic, response, and treatment, and get more meaningful information that helps everybody, and helps the horse in particular.”
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