The reason laminitis in horses increases in the fall is fructan, a plant sugar that contributes to metabolic imbalances that can lead to laminitis. Produced during photosynthesis, fructan is a fuel source that helps the grass grow. Levels of the sugar taper off when the plant reaches maturity but they can can increase again when grass regrows—after a drought, for example. Fructan levels also rise when sunny days, which allow for more photosynthesis, are followed by cool evening temperatures, which slows the growth of the grass. In the fall, even grass that appears to be stressed and dying can be high in fructan.The risk of laminitis in the spring—when horses graze lush new pasture grass—is well understood, but fewer people are aware that cases of laminitis, a devastating hoof condition, also spike in the fall.
If your horse is at risk of developing laminitis—he is insulin resistant, obese or has a history of laminitis—keep him off grass and in a dry lot until your pasture goes dormant for the year. A grazing muzzle can also help control grass intake. Ask your veterinarian for advice if you’re unsure of your horse’s risk of laminitis or when it is safe to let him have access to grass.