Franklin Vets Blog

The dangers of sweet spring grass

October 16, 2019

Horses are grazers designed to use fibrous material (such as grass and hay) as an energy source. However, the grasses horses were designed to eat are much lower in sugar and slower growing than the grasses we commonly grow in this region. Therefore, while grass, hay etc. remain an important part of our horse’s diet, there are a few things we should be aware of which can cause health and behaviour issues.spring grass

High blood sugar levels

Just like us, if you feed horses more energy than they use they will gain weight. High grass sugars from tasty spring and early autumn grass can cause further problems such as Equine Metabolic Syndrome where horses become overweight and have a range of increased disease risks (such as laminitis) related to high blood sugars. Breeds such as minis, Welsh ponies, cobs, and donkeys are more susceptible.

Paddock restriction, a hay diet through spring & autumn, and regular exercise will all help with normal sugar metabolism.

Hindgut acidosis

The lush pasture of spring brings an increased risk of sugar entering the large colon where it feeds bacteria that produce gas and lower the pH, disrupting normal fibre digestion. This can lead to colic; less severe signs include poor condition, change in faecal consistency, and abdominal discomfort. We advise restricting grazing during these conditions and feeding hay whilst the grass matures, and the digestive system adapts. There are many products to help counteract acidosis, including antacids, pro and/or pre-biotics and Equinate. Talk to your vet about which would be best for your horse.


Magnesium is important to muscle and nerve function however, the high potassium in ryegrass pasture reduces its absorption and pasture tends to have lower levels of magnesium in spring. Many grazing horses with nervous, excitable behaviour during the spring and autumn respond to magnesium supplementation.

Ryegrass staggersryegrass

This nervous disease affects horses in late summer/early autumn after they have grazed endophyte-affected ryegrass pastures. It takes several days for signs to be seen which include head & neck tremors, muscle flickers, stiff gait, and uncoordinated movement. Place horses in a safe area free from obstacles (including wire fencing) and remove from ryegrass paddock, taking care not to feed hay that is late summer/autumn cut and/or from high-risk pasture. Toxin binders may help.

Kikuyu grass

Unfortunately, Kikuyu binds calcium so may cause calcium to phosphorus ratio imbalance leading to bone deformity affecting the skull most obviously. Pregnant mares, foals and young horses are at the highest risk due to high calcium demands. This can be counteracted by supplementing calcium in the feed. Wheat bran feeding is also associated with this imbalance so should be avoided when horses are on predominantly Kikuyu grazing.

If you have any concerns, please contact the Franklin Vets Equine team: 09 238 2471

Dr Katie Kindleysides BVSc CertAVP (Equine Dentistry)