01/06/2026
❄️June 1st marks the start of winter in NZ, but don’t worry — check out the informative info below to help you manage the cold and keep your horses nutritionally safe, warm, and happy this season!❄️
Grass growth and seasonal fluctuations of sugar levels increase the risk for equines who are sugar sensitive or pre-disposed to laminitis. For owners of these horses, it is vital to understand how grass grows, the impact on sugar levels of frosts, and solutions to this problem.
How does grass grow?
Green plants—like grass—create sugar through photosynthesis:
Carbon Dioxide + Water + Sunlight = Sugar + Oxygen
The plants then use this sugar for growth and reproduction, a process called respiration:
Glucose + Oxygen = Carbon Dioxide + Water + Energy for growth/respiration
When more sugar is created than the plant requires, the excess is stored as fructan or starch (carbohydrates) for later. Plants will respire (grow) whether dark or light, while only photosynthesizing in light. An increase in light leads to an increase in the rate of photosynthesis—Therefore:
- No light (Nighttime): respiration rate is higher than photosynthesis
Dim light (Cloudy days): photosynthesis is at the rate of respiration.
- Bright light (Sunny days): photosynthesis rate is higher than rate of respiration.
How is sugar level impacted by frosts?
Under normal conditions—when the temperature is above 5°C—grass undergoes sugar accumulation during the day. Given that more light creates more photosynthesis, and on sunny days the grass will photosynthesize better than it can respire: the sugar levels are highest at the end of the day and lowest around 5AM. However, an exception to this is frosty conditions, when the temperature is too low for grass growth.
Frosts result in heightened sugar levels, as they are stored in the plant to be ready for when the grass can grow. It is important to note that the high sugar levels will remain in the grass even if there are sunny days with the frosts—it is only when the temperature is consistently above 5°C that the plant will begin to respire again. So, when there are frosts, the excess stored sugar increases the risk for sugar sensitive or laminitis prone equines.
So, what do we do?
There are several options to manage the risk posed to your horse during frosts:
One option is to turn your horse out during the night and bring it in during the day. This means you are dodging the excessive sugar build-up as your horse isn’t grazing while the plant is photosynthesizing. When your horse is off pasture, remember that you need to replace the pasture eaten during the day with another forage. A low sugar option to replace some of your horse’s fibre with Fiber Protect, Fiber Ezy or Fiber Meadow is a great way to mitigate the risk associated with frost-affected pasture. Top tip: Horses have a natural drive to eat around 6pm in the evening, so ensure you don't finish work and send them out to pasture on an empty stomach. Make sure you fill them up with Fiber Fresh before putting them out to prevent overeating and undoing all your good work!
Soaking hay is also an option to remove sugars; however, depending on your starting sugar level of your hay, it may still be too high for horses that are sensitive, even after soaking! It can also alter the microbiome of the forage to be less desirable for gut health (Daniels et.al 2020).
Feeding quality fibre sources such as Fiber Meadow, Fiber Ezy and Fiber Protect can help eliminate the variability of sugars in their diet. Meadow, Ezy, and Protect all contain some of the lowest starch and sugars in a fibre source that you can provide your horse or pony with.
For laminitis-prone horses, these products are especially useful. The Laminitis Society recommends that horses with conditions exacerbated by high sugar levels consume forage fibre with Non-Soluble Carbohydrates (NSC) and sugar levels no higher than 10% to 12% per kg of dry matter.
