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Transitioning to Pasture

by Dr Clair Thunes PhD Nutrition
Consulting Nutritionist for EnviroEquine & PET
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Across the country spring is coming and with it that means lush green pastures. You know your horse has been waiting for this moment throughout the long dark winter and you just can’t wait to let him out. But you should wait because too much grass introduced too quickly can have devastating consequences including diarrhea, colic and laminitis. So what steps can you take to reduce the risks of these potentially life threatening conditions?

First of all wait until the grass is tall enough to be grazed. This would be a height of about 6 to 8 inches tall. Grass grazed before this height will not have enough leaf on it to be able to sustain grazing and ultimately the roots can become damaged which negatively impacts the pasture’s ability to be grazed over time. Graze down to a height of about 3 to 4 inches and then rest the pasture to allow growth to get back to 6 to 8 inches before grazing again. This will insure the longevity of your pasture.

Next consider that you horse has not been eating pasture for several months. Pasture grass has a widely different nutritional profile than dry hay. For one thing it can contain as much as 85 percent water versus hay which is typically around 90 percent dry. The carbohydrate composition of young grass is quite different than more mature grasses cut for hay. Young grass typically contains more non-structural carbohydrate (NSC) and less fibrous material.  Higher sugar content can lead to elevated blood glucose and insulin which for horses with insulin resistance can lead to laminitis. Additionally the shift in carbohydrate content can disrupt microbial fermentation in the hindgut. The microbes in the hindgut are specific to the diet being consumed and take time to adapt to dietary changes. Sudden changes can lead to microbial death and the release of toxins which may also lead to laminitis. Rapid fermentation of easily fermentable carbohydrates in grass pasture can cause gas production, colic symptoms and the changing microbial population may result in diarrhea.

So what can you do to reduce the risk to your horse this spring? Experts recommend starting horses on pasture slowly. Start with 15 minutes, and every day increase the grazing time by 15 minutes until your horse is grazing for 4 to 5 hours. From here horses should be able to graze safely for longer periods of time. However you should always consult with your veterinarian if your horse has metabolic conditions, is overweight or has a history of previous laminitis. Such horses may not be able to graze safely for long periods or at all. Watch for any suggestion of gastrointestinal disturbance and reduce grazing time if needed. Feeding GastroBalance Plus may also be of benefit to horses transitioning to pasture. The live yeast and other prebiotics help to stabilize the gastrointestinal tract bacterial populations and the bentonite clay helps support normal manure production.

Consulting Nutritionist for EnviroEquine & PET Dr. Clair Thunes is passionate about her profession—one that she decided upon at the age of 14. After earning a Bachelor of Science with Honors from Edinburgh University, and a Master of Science in Animal Science and a PhD in Nutrition from the University of California, Davis, Dr. Thunes went on to found Summit Equine Nutrition LLC an independent consulting company in 2007. An experienced nutritionist and accomplished scientist, Dr. Thunes understands the vital role that nutrition plays in managing horses today. Most importantly, she believes in making nutrition accessible to everyone and removes the guesswork so that owners have the peace of mind that their horse’s diets are optimal for maximum health and peak performance.  Her clients include all horses from competitors at the 2016 Rio Olympics to retired pasture friends, mules and miniature donkeys. She writes a weekly online commentary for and her nutrition articles have been published in noted publications including: The Horse, Equine Wellness, Trail Blazer, Horse & Rider and The Horse Report. Besides consulting she teaches equine nutrition and equine exercise physiology in the Animal Science Department at UC Davis and equine health at Cosumnes River College.  Clair continues to be involved with The United States Pony Clubs, Inc. and she is currently the Regional Supervisor for the Sierra Pacific Region.

Top Photo: © vicushka / 123RF Stock Photo