To feed your horse the best forage for his needs, you have to understand the plants and what affects their nutrient content, said Jerry Chatterton, PhD, Research Leader of the USDA Agricultural Research Service, Forage and Range Research Laboratory in Logan, Utah. He spoke at the Equine Forage: Risks and Rewards Seminar and Summit held Oct. 22-23 at Rutgers University.

He explained that there are two types of carbohydrates in forages: Total non-structural carbohydrates (TNC), which are inside the cells and include sugars, starch, and fructan (a type of sugar); and structural carbohydrates in plant cell walls, which include cellulose and hemicellulose. The TNC are the ones that can cause problems in chronically laminitic and/or metabolically challenged horses.

A plant’s levels of TNC vary with its rate of photosynthesis and respiration. In a nutshell, Chatterton explained that photosynthesis is the plant’s creation of sugars from sunlight energy, water, and carbon dioxide; respiration converts those sugars into energy for growth.

“When the rate of sugar synthesis (photosynthesis) exceeds the rate of sugar utilization (respiration and growth), non-structural carbohydrates accumulate in many plant parts–leaves, stems, and roots,” he said. Conditions under which this can happen are very sunny days (driving lots of photosynthesis) and cool nights (slowing respiration’s utilization of the sugars)