Current news is available at, Equine Guelph's online learning platform for practical, quick learning. Given the vast amount of information on horse health and welfare, Equine Guelph has archived its past news articles from 2002-2020. They are listed below, along with a search function available to find specific healthcare topics.

Fast Forage Switches Not Recommended for HorsesOctober 2019

Story by: Jackie Bellamy-Zions

Close-up of a horse eating hay Do you know the first signs your horse’s digestive system is in danger? Diarrhea, upset stomach, or in the worst case scenario--colic can all be caused by too quick an adaptation period from one type of forage to another. Whether it is moving barns, moving to a new batch of hay from the supplier, or switching from a lush, moist, grassy paddock to a dry sandy sacrifice paddock and dry hay, the importance of switching forages slowly cannot be overstated. Using an adaptation period of 10 – 14 days to transition new feeds into your horse’s diet is recommended.

  Day 1 – 3 Day 4 - 6 Day 7 -10
Old Hay 75% 50% 25%
New Hay 25% 50% 75%

Forage makes up the largest portion of the horse’s diet and using an adaption period is of utmost importance when introducing a new forage source to your horse’s diet. A change in hay/pasture has been associated with the highest risk of colic (Hillyer et al., 2002).

Educated horse owners take great care when introducing horses to spring grass in order to avoid health issues but they are not always as judicious when pulling horses off grass in the late fall and early winter. “Switching from a grass to a legume hay, and also from a fresh grass pasture to a dried grass or mixed hay, it is beneficial to add a 'yeast culture' or a 'prebiotic' into their diet for 10 to 14 days while making the transition,” says highly experienced equine nutritionist Don Kapper.

Understanding the inhabitants of your horse’s gut makes it easy to grasp the importance of making dietary changes slowly. The quantity and type of microbes living in the gut will be determined by the ‘type’ of forage being eaten. It takes different microbes to ferment and breakdown grasses than it does legumes. Loose stools and digestive upset are common results from making a fast change in forage type, for example: If you are switching from a timothy grass hay to a legume hay, like alfalfa. There will simply not be enough of the correct ‘type’ of microbes available to help with fermentation and the horse’s health will suffer.

“Loose stools are a sure sign that the colon is not doing its job of reabsorbing water and forming the stools,” says Kapper. “That is why the Pre-biotics are recommended to help whenever the stools become soft or loose enough to cause diarrhea. Because we are dealing with the health of the microbes in the colon, a 'treatment' level should be administered for five additional days after the stools become normal. Pre-biotics are a 'food' to help the microbes stay healthy, grow and multiply, and are colon specific as opposed to Pro-biotics. The majority of the Pro-biotics will not make it back into the colon.”

Discuss your options with an equine nutritionist to help you choose the right product for your horse.

Forage is the bulk of the horse’s diet. To keep your horse’s microbes happy, making changes to feed slowly is important; even more so for forage than grain mixtures. Want to learn more about best practices for a healthy equine gut? Take the next offering of Gut Health & Colic Prevention at

Equine nutritionist Don KapperEquine nutritionist Don Kapper (Professional Animal Scientist) 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.

Table 1: How to transition feedstuff in your horse’s diet

Photo Caption: Forage is the bulk of the horse’s diet. To keep your horse’s microbes happy, making changes to feed slowly is important.