11/06/2025
When the air gets crisp and you see frost on the grass, your pasture is changing more than you might think.
Here’s why that matters:
During the day, grass uses sunlight to produce sugars through photosynthesis. Normally, those sugars are burned for growth or stored in the roots overnight. But when it’s too cold, typically below about 5°C, grass growth slows or stops completely. That means those sugars stay concentrated in the leaves instead of being used up.
The result is that on bright, sunny days followed by chilly nights, the blades of grass can contain unusually high sugar levels.
Cool-season grasses, such as timothy, brome, orchardgrass, and fescue, are especially prone to this. These species thrive in cooler weather and naturally accumulate more sugars to help them survive cold stress. When temperatures fall, they can’t use those sugars efficiently, which causes even higher concentrations in the leaf blades.
For horses with metabolic syndrome, insulin resistance, or a history of laminitis, that sugar spike can pose real risks, turning an ordinary pasture into a sugary treat their system can’t handle.
How to keep your horse safe in cold weather:
- Avoid turnout on frosty mornings when sugar content peaks.
- Turn out later in the day, ideally mid to late afternoon, once the grass has used up more sugar.
- Use a grazing muzzle or limit turnout time if needed.
- Feed tested, low NSC hay when the weather stays cold.
- Keep an eye on insulin levels and body condition. Early monitoring can help prevent flare ups. Ask us about our simple insulin testing options.
Cold weather doesn’t have to mean no pasture time. It just means smarter management. Understanding how grass responds to temperature shifts, especially in cool-season pastures, can help keep your metabolic horse healthy and comfortable all winter long.
