Ask SAM: Just say 'Whoa!' to early spring grazing

This column is provided by Larimer County Extension's Small Acreage Management (SAM) Program to assist rural residents.

Dear SAM,

I'm so happy winter is over! Can I let my horse out onto the pasture now?

Julie

Dear Julie,

Spring is here. Dusty hangs his head over the fence, drooling for some fresh green grass. In your heart, you want to pamper him. Should you open the gate?

Base your decision to begin spring grazing on grass growth, not the dietary desires of your animals. Most of our cool season grasses should be about 8 inches tall before grazing begins. This typically occurs in late April or early May. Until then, animals should be kept in a dry lot, completely off the pasture.

When grass is tall enough for grazing, manage the transition carefully. Most horses have been eating dry hay during winter months. Hay is high in fiber and low in soluble carbohydrates. The animals' digestive systems have adjusted to this forage.

Young grasses in a spring pasture are high in soluble carbohydrates and low in fiber. When a large amount of soluble carbohydrates suddenly enters a horse's digestive system, the microbial balance in the gut is disturbed. As the microbial population shifts, large numbers of bacteria die. And as they die, the bacteria release endotoxin. As you might guess from the name, "endotoxin" is not a good thing.

The released endotoxin enters the blood stream and can cause laminitis, or grass founder. Horses with a history of laminitis, overweight horses, and those with Cushing's disease are at highest risk. Ponies and donkeys are more susceptible than full-sized horses. The University of Missouri reports that spring grass grazing by overweight horses is the leading cause of laminitis in equines.

To avoid health problems, introduce animals to fresh grass slowly. Feed hay before pasturing to reduce the animals' appetites. Give horses access to pasture for 15 minutes on the first day of turnout. Increase turnout time by 5 minutes per day for subsequent turnouts. By gradually shifting the diet, the digestive system can adjust slowly without a sudden shock to digestive system microbes.

Not all animals have the same reactions to dietary changes. While Trigger might do fine with the transition to grass, Sparky might be having problems. Manage animals according to their individual needs, regardless of the rest of the herd.

The risk of laminitis increases with overgrazing. Carbohydrate concentrations are highest toward the base of grass plants. Leave at least 3 inches of grass height in the field. Limit grazing time, wait for adequate grass growth and avoid overgrazing to ensure better health for both the animal and the land.

SAM

Have a question about rural living? Write to Ask SAM, Larimer County Cooperative Extension, 1525 Blue Spruce Drive, Fort Collins, CO 80524 or e-mail emarx@larimer.org.