Safe Grazing for at-risk Horses

When a horse suffers from certain metabolic conditions, unmanaged grazing can be detrimental to their health.  A horse suffering from Cushing’s, insulin resistance or other metabolic conditions often needs to limit their intake of carbs, specifically non-structural carbohydrates(NSC) i.e. sugar, to keep their symptoms under control.  Plants store their energy in the form of sugar, so grazing when the plants’ energy stores are at their lowest is a good way to keep NSC consumption to a minimum.  The time of year, time of day and type of grass should be taken into consideration before turning your horse out.  

Grasses use sunlight to create carbohydrates (photosynthesis) and store them to use as energy for growth overnight.  This means the NSC content is highest in the evening since they are storing energy to be able to keep growing overnight.  Typically the best time of day to turn out an at-risk horse is early in the morning since at this point the grass should have used up most of its energy stores overnight and has not had a chance to make more yet.  This can vary with the time of year and environmental conditions; if the grass is in a drought situation, excessive heat or an overnight freeze, then growth is slowed, therefore less energy is used and the grass will have a higher than usual NSC content in the morning.  Cloudy conditions can also affect how much NSC is made by slowing the process of photosynthesis, decreasing how much sugar is made.   

The type and variety of forage you are growing will also affect how much NSCs are being stored.  Cool season grasses, such as Orchard, Timothy or Ryegrass are typically higher in NSCs than warm season grasses such a Bermuda; however it can still vary greatly between varieties of the same grass.  It is unclear as to exactly what the effects of legumes in the diet of an at-risk horse are, so they should be grazed with caution.

Grazing management is an important tool in managing certain metabolic disorders and under the supervision of a vet can help get your horse back to a happy and healthy life.