New season, new grass: Colic alert for horse owners


With the change in season horse owners are being urged to be mindful of the risks of colic.

While horse folks are generally good about making changes to their horse’s grain rations over a two-week period to prevent hindgut issues such as colic and diarrhea and reduce the risk of laminitis, pasture is not always thought of in the same way.

But spring grasses are higher in Non-Structural Carbohydrates, (NSC’s), starch and sugars, like fructan and low in fibre, especially during rapid growth phases.

To keep your horse’s digestive system healthy, the gradual introduction of new forage (including pasture) is very important. The nutritional composition (e.g. the amount of protein, sugars and types of fibre) varies greatly between forage types, and especially between hay and newly growing spring pasture. The bacteria in a horse’s gut need time to adjust to these changes.

A sudden increase of fresh spring grass in a horse’s diet can change the pH in the hindgut and cause all sorts of health issues. Spring grass, low in fibre, is rapidly fermented, and an overload of starch enters the cecum killing off microbes important to digestion.

Don Kapper

Equine nutritionist Don Kapper says the first sign you will see is a loosening of the stools.

When excessive fermentation creates a buildup of gas in the gut this is when gas colic can occur. The stretching of the intestinal wall from the gas build up causes considerable pain. A veterinarian should be consulted whenever colic is suspected. Gas colic is often mild, but it can also lead to a twist in the gut that would require surgery.

“If the horse is turned out 24/7, mother nature will take care of your horse’s gradual introduction to spring pasture,” says Kapper. “The grass grows slowly, and they will continue eating hay on the side.”

For the horse that is stabled, the stable manager must limit the amount of new growth the horse is exposed to in the pasture each day. First, let the grass paddock grow to about six inches. Start with just one hour of turn out per day on the lush grass pasture before putting them back in their sacrifice paddock or dry lot where they have been all winter. That can be slowly increased by 30 minutes to an hour every other day.

Consider turn-out very early in the morning when NSC concentrations are lower (NSC concentrations increase throughout the day with increasing sunlight). However, if there has been frost overnight, NSC’s will accumulate in the grass. In this instance, you will want to restrict turn-out, Kapper says.

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Requirements of “metabolic horses”

Kapper makes a clear distinction between the management of horses diagnosed with metabolic issues and the rest of the herd. The metabolic horse requires a diet low in NSC’s and may be best managed on a dry lot, with hay as the only forage. One must always work with their veterinarian when planning the best options for the care of the metabolic horse.

Horses generally avoid poisonous plants unless there is nothing else to eat. Being diligent with pasture maintenance pays off not only in the reduction of weeds but in the ability to use your pasture to help fulfill your horse’s forage needs.

With a higher moisture content than hay, there is great value in being able to provide pasture to your horses. It is good for your budget and good for your horse’s overall health if introduced with caution.

Kapper’s advice is outlined in Equine Guelph’s free Colic Risk Rater Tool, which helps horse owners assess their management practices.

His top 10 tips:

  1. Introduce spring grass gradually, increases of 30 minutes to an hour every other day
  2. NSC concentrations are lower early in the morning except when overnight frost occurs.
  3. Keep hay in front of your horse at all times. Chew time=saliva=healthy pH in the gut and reduces the chance of digestive issues.
  4. As little as 4 hrs without forage can have a negative impact on gut health.
  5. Signs of not enough fibre: loose stools, eating dirt, fences, manes & tails, trees.
  6. Mow weeds as soon as you see them start to flower (in spring about every 3 weeks)
  7. When mowing pasture set the mower 6 inches from the ground.
  8. If stools loosen during a change in forage, brewer’s yeast can provide a good culture for microbes in the horse’s gut. Pre-biotics could also prove useful.
  9. Consult your veterinarian for diet and management advice for metabolic horses; they are very susceptible to issues when starch is even slightly elevated.
  10. Spring pasture maintenance begins with a soil test checking for an ideal pH between 6.5 & 7. From there you will know what to add in lime and then what to add to your fertilizer.

Don Kapper is the author of the chapter on “Applied Nutrition” for the authoritative veterinary textbook: “Equine Internal Medicine”, 2nd edition and was a member of the “Performance Electrolyte Research” team at the University of Guelph. He is also a frequent guest speaker in Equine Guelph’s online Nutrition courses and online Gut Health and Colic Prevention course.

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