How Do I Transition My Horse to Pasture?

How Do I Transition My Horse to Pasture?

Transitioning your horse to pasture safely takes time. Start by grazing your horse about 15 minutes and each day increase the time on pasture by 15 minutes until your horse is on grass for about four to five hours per day.

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Q. I've been feeding my horse hay all winter. What advice do you have for safely transitioning from hay to spring pasture?

A. If spring hasn’t arrived yet where you live, it’s likely right around the corner. And with the new season comes spring grass. Most of us love the idea of our horse grazing green pastures. But before you take advantage of this wonderful resource there are things you should do to ensure your horse remains healthy and your pastures stay in good shape.

Consider the Horse’s Digestive Tract

Your horse’s digestive tract has become adapted to the diet that you have been feeding all winter. This means that hindgut bacteria are honed on utilizing whatever type of hay you’ve been feeding, and enzymes in the small intestine are prepared for certain types and levels of carbohydrates, fats, and proteins. These adaptations take time to change, so you need to slowly transition your horse to pasture grazing to safeguard his digestive health.

Sudden changes in forage sources, especially to pasture (which has a higher water content and potentially a very different carbohydrate profile than hay) can lead to hindgut disruption. If consumed in too great a quantity, starch and sugar that should be digested and absorbed in the small intestine might reach the cecum and colon, where they can cause rapid fermentation and gas production. Fructan sugars that exist in cold season grasses can have the same effect. This shift to readily fermentable carbohydrate results in lactic acid forming in the hindgut.

Small amounts of lactate are “mopped-up” by lactate utilizing bacteria. But if these bacteria’s capacities are overwhelmed, lactic acid starts to build up resulting in a lowered hindgut pH. The result can be subacute lactic acidosis and a horse that shows colic symptoms, diarrhea, and gas. If the hindgut pH continues to drop, the situation can spiral out of control and cellulolytic bacteria that ferment complex carbohydrates might start to die off, releasing toxins that can pass in to the blood stream. Ultimately these toxins could lead to laminitis.

The shear amount of sugar in some grass or the quantity of grass consumed by eager individuals might result in high-circulating glucose and insulin. For horses that are insulin resistant, this poses a major risk factor and increases the likelihood of a laminitic event. If you have a horse that has a history of laminitis, is overweight, or is insulin resistant (IR), discuss with your veterinarian whether any amount of pasture grass is safe for your horse. 

Certain equine breeds appear to be more IR-prone, and it’s wise to ask your veterinarian whether your horse is one of these breeds and discuss what measures you might need to consider to keep your horse safe.

Take Time to Transition

Transitioning your horse to pasture safely takes time. Start by grazing your horse about 15 minutes and each day increase the time on pasture by 15 minutes until your horse is on grass for about four to five hours per day. From here it should be safe to allow your horse continuous access.

Avoid Overgrazing and Pasture Stress

Beyond your horse’s health, you want to keep your pasture healthy, as well, so it remains a viable resource all year long. This means not overgrazing.

Overgrazing is a function of time, most notably the time that a pasture is given to recover from being grazed. Grazing pastures that haven’t reached about 6 to 8 inches in sward height can result in damage that’s impedes pasture recovery.

Ideally, wait until grasses are 6 to 8 inches high to initiate grazing and stop grazing when horses have reduced grass height by 3 to 4 inches. This leaves enough grass leaf for photosynthesis, which and generates nutrients that are delivered to the roots. Grazing lower than this limits the plant’s ability to generate the energy it needs to regrow. When this cycle occurs repeatedly grasses can die and bare patches might result.  

The relative amount of nonstructural (NSC) carbohydrate is greater in younger grasses. As a grass matures it becomes “stemmier” and the proportion of NSC goes down while the less digestible carbohydrate goes up. Pastures that incur more stress from overgrazing might also have higher sugar contents. Therefore, waiting until plants are a little taller before grazing benefits not only the pasture, but also your horse.

Other management protocols such as correct irrigation practices and fertilizer applications can also help reduce pasture stress.

Seek Expert Advice

If you are unsure how to manage your pasture in a way that protects it and your horses, reach out to your local university extension agent. He or she should be able to help you determine correct management practices for your pasture based on your geographic location, pasture acreage, and stocking density (number of horses in a given pasture).

Take-Home Message

By taking the time to introduce your horse to pasture slowly combined with the implementation of a well-thought-out management program, you can maintain the value of your pasture as a resource while safeguarding your horses well-being.

About the Author

Clair Thunes, PhD

Clair Thunes, PhD, is an independent equine nutrition consultant who owns Summit Equine Nutrition, based in Sacramento, California. She works with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the United Kingdom Pony Club. Today, she serves as the regional supervisor for the Sierra Pacific region of the United States Pony Clubs. As a nutritionist she works with all horses, from WEG competitors to Miniature Donkeys and everything in between.

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