October Blog: The Dangers Of Spring Grass

Oct 28 2020

The days are longer, warmer and the grass is finally growing- it must be spring! However, for some horse owners spring is not something they look forward too. During winter,  grass growth slows down and the fructans (sugar) in the grass is low, however when the weather begins to warm up in spring, grass growth increases and as a result the nutrients in the grass increase, including fructans. Many New Zealand paddocks are full of “improved” grasses made for producing good meat and milk quickly and effectively- This means these grasses are FULL of nutrients. This sounds great- However, horses are designed to eat poorer quality, slower growing grasses that are much lower in sugar. Because of this, there are a few things horse owners need to be aware of in spring.

Grass affected horses

A ‘Grass affected horse’ is one where one or multiple aspects of their diet are adversely affecting their health and behavior. This usually originates from the forage (grass) but can be further exacerbated by the addition of other potassium rich feeds to their diet. If a horse is  “grass affected” owners may notice some behavioral changes. A grass affected horse can become hyperactive, spooky, tense, touchy,  girthy or may even begin to buck under saddle. In bad cases, horses can become very unpredictable and even dangerous to handle. The cause of this behavior can be for multiple reasons; an increase in protein/energy levels, hind gut acidosis caused by a sudden increase in fructose or even mycotoxins.

Grass Staggers

Grass staggers is a seasonal condition that is caused by lolitrem- a fungal-produced mycotoxin, found in ryegrass pastures. These mycotoxins flourish in spring as it is damp and warm, horses inadvertently eat this toxin when grazing in pastures with ryegrass. Signs of staggers may develop 7-14 days after exposure and are the result of the toxins affecting the horses central nervous system. Mildly affected horses will show signs similar to that of a “grass affected horse”; Nervous, spooky, sensitive to sudden movement or noise. Severely affected horses will show head nodding, staggering, falling, loss of coordination, tremors and even hind quarter paralysis. Recovery is usually spontaneous once the horse has been removed from the pasture.

Obesity and Laminitis

As mentioned above; The pastures that horses graze on today are very lush compared to the diet they evolved to eat, and they are no longer required to cover great distances to find it. This has led to a relatively high percentage of horses that are obese. Equine obesity and the influx of calories and nutrients from spring grass can also cause laminitis.

Laminitis results in the destruction of the sensitive, blood-rich laminae that connect the horse’s hoof to the soft tissue of the foot.  The sensitive laminae interlock with insensitive laminae lining the hoof, much like interlocking fingers to keep the coffin bone in place within the hoof. This destruction of laminae can result in rotation of the pedal bone or even sinking of the bones and sensitive foot structures through the hoof capsule. Laminitis is an extremely painful condition for your horse and treatment is a long, slow process with no guarantee of a full recovery. If you suspect your horse has laminitis you should seek veterinary attention immediately.

Diarrhea and colic

When the sugar content in the grass suddenly increases it causes the bacteria in the hindgut to produce a lot of gas. If these gasses are produced too quickly or not passed rapidly, it can cause colic. “Young”, lush spring grass contains more protein and less fiber, which speeds up digestion and transit time,  this on top of the increase in fructans, can cause hind gut acidosis and diarrhea.

There are a few things you can do to prevent the above conditions:

  • Introducing spring grass gradually to horses who have been on hay-based diets over winter
  • Avoiding pastures with an abundance of ryegrass where possible
  • Restricting pasture access if your horse is overweight or prone to becoming grass affected
  • Taking your horse off the grass and feeding soaked hay at high risk times or if they begin to show any signs of becoming grass affected
  • Ensuring your horse has an adequate supply of fiber and a nutritionally balanced diet
  • Regularly checking your horses body condition score and adjusting their diet if necessary
  • Most importantly- Ensure you discuss all feed and management options with your vet to find the best option for you and your horse

With the correct management and an understanding of the warning signs, your horse should come through spring problem free! It is important to note, if you think your horse is suffering from any of the above, you should seek the advice of your vet immediately. Also, Your horse should not be transported if it is showing any of the above reactions to spring grass,  this could worsen your horses condition and put your horse and any handlers at risk.

Information sourced from;

Jenny Paterson B.SC, Calm Healthy Horses Ltd 2013, Accessed October 2020, <www.calmhealthyhorses.co.nz>

Vet Pro 2021, Accessed October 2020, <Vetpro.co.nz>

Thomas R. Lenz, DVM, M.S, American Association Of Equine Practitioners 2020, Accessed October 2020,<aaep.org/horsehealth/grass-founder>

Totally Vets 2021, Accessed October 2020, <www.totallyvets.co.nz/portfolio,portfolio,,1073,Spring+grass.html>

Book trip Services Contact