Spring Grass Safety

Not all pasture grass is created equal. Although this forage cornerstone of the equine diet offers excellent nutrition, provides fiber to keep the horse’s digestive tract healthy, and allows the horse to satisfy his innate need to graze, come spring it is also notorious for causing causing problems. This is particularly true in horses at risk for digestive or metabolic disorders. 

 

“Spring pasture grasses are capable of accumulating high amounts of nonstructural carbohydrates (NSCs), which are implicated in acute equine digestive diseases associated with rapid fermentation, and chronic metabolic disorders,” says Bridgett McIntosh, PhD, assistant professor and horse extension specialist at the University of Tennessee. The types of NSCs found in grasses fall into three categories: sugars (glucose, fructose, sucrose), starches, and fructans. 

 

“The NSC content of grass varies widely depending on environmental conditions, plant species, and stage of growth,” McIntosh continues. “Through photosynthesis, grasses use light to produce sugars from carbon dioxide. When sugars are produced in excess of the plant’s energy needs for growth and development, they are converted into storage, or ‘reserve,’ carbohydrates.” 

 

Grasses are classified as either warm-season or cool-season, based partly on their growing cycle throughout the year and also on how and when they metabolize and photosynthesize sunlight to produce carbohydrates. 

 

“Fructans are the primary storage carbohydrate in cool-season grasses (tall fescue, orchardgrass, and timothy), while starches are the primary storage carbohydrate in legumes (clover and alfalfa) and warm-season grasses (Bermuda grass, crabgrass, bahiagrass),” McIntosh says.