Green Grass: Approach with Caution

Green Grass: Approach with Caution

Spring has sprung, summer’s here, and green pasture is coming on like gangbusters in many parts of the country.


Spring has sprung, summer’s here, and green pasture is coming on like gangbusters in most parts of the country.

For most of us this is good news, because green grass relieves some pressure from searching for reasonably priced high-quality hay. If you have pasture and intend to use it for horses, however, there are some things to consider.

Keep in mind that going from dry hay and grain to lush, green pasture is a drastic change in a horse's diet and can increase his risk of founder or colic. Horses that are on pasture full time will gradually become accustomed to the emerging green grass. But horses that haven’t had green grass should only be allowed to graze for an hour or two at first, then gradually increase grazing time by an hour every couple days until the horse is out full time.

Also allow horses to eat dry hay prior to turnout so they are not overly hungry. Individual horses will have different tolerance levels to the diet change and the grass' nutritional profile, so the slower the introduction, the better.

Spring and early summer pasture, depending on your region, often looks beautiful and nutritious but can be very high in water and low in fiber content. In this stage of maturity, pasture alone might not meet a horse’s minimum requirement for dry matter intake, and it might be necessary to provide supplemental hay until the pasture matures.

Even when the pasture is sufficient to maintain horses in good body condition with no supplemental grain, it will still likely have nutrient deficiencies. Providing a ration balancer product can help supply a balance of protein, vitamins, and minerals to compliment pasture.

Pasture simulates a natural environment for horses and is considered healthy from a nutritional standpoint, as well as from a low-stress, mental-health perspective. You might have enough pasture to serve both functions, but in some cases available pasture is limited to a place to move around and nibble for a few hours a day rather than a horse's sole nutritional source. Consider acreage and number of horses to determine if you have enough pasture to provide adequate grazing for the grass to play a significant role in your horses’ diet.

The very best pastures might support one horse per acre, but most conditions will require closer to two to three acres to sustain one horse grazing full time. The effective stocking rate will depend on the type of grass, fertilization, and rainfall.

Shorter varieties of grasses, such as Kentucky bluegrass, must grow three to four inches tall to provide adequate forage for horses. Taller grasses, including Coastal bermudagrass, should sustain a height of six to eight inches. Stocking rates can be slightly higher if you rotate pastures:

Grazing tall forage varieties down to three to four inches and shorter varieties to two inches in height, then rotating to another pasture for about four weeks can help maximize grazing potential of available acreage. Rotating pastures is also a good way to reduce the risk of internal parasite infestation.

A good rule of thumb is that if manure piles are visible and horses are grazing close to those manure piles, the pasture is likely overgrazed and horses should be removed to let it recover.

About the Author

Karen E. Davison, PhD

Karen Davison, PhD, is an equine nutritionist and sales support manager for the horse business group at Purina Animal Nutrition. Her expertise includes equine nutrition, reproduction, growth, and exercise physiology. She received her MS and PhD from Texas A&M University.

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