Over the past five years, vet Stephen Ashdown has written many articles, spoken on equine matters and contributed widely to horse magazines.

Here he reproduces in the form of questions and answers about 100 topics, all of them common problems which afflict horses.

To access Topics click on Vet Advice Menu.

Devastated by grass sickness
Q. In September last year I lost my horse to grass sickness. Her symptoms started in the morning and by evening she was put to sleep.

She was a 'good doer' and at the time was being grazed in a sparse paddock along with a Shetland pony. My horse was fit and healthy 16 year old mare, who had never suffered a bout of colic in the 10 years I owned her. Do you have any more information about this condition?

A. It is very sad to hear you have lost your horse to grass sickness. Unfortunately, the cause of this disease is unknown, but it is thought that it may be due to a toxin that damages the nerve supply to the bowel and other organs. The origin of this toxin is most likely to be in the pasture, but, as with your Shetland pony your horse shared the field with, it only affects certain individuals. Most case occur during the summer among horses in good condition which have recently been stressed (any form of stress weakens the immune system). Mild forms of grass sickness result in weight loss and mild tremors, but in its worst form it causes severe pain, shaking and regurgitation. At this stage the most likely action, in order to avoid suffering, is euthanasia.

It is often difficult to know how to treat cases of grass sickness effectively, and it requires careful nursing and fluid therapy. Some vets may give drugs to help the bowel work more effectively and probiotics may be useful. Antioxidant supplements can aid recovery and strengthen the immune system to prevent the problem recurring.

If you suspect that a horse has grass sickness, particularly if he is on grazing land where it has happened before, a vet should be contacted immediately as prompt action is vital. However, don't worry too much, as it is unlikely that a case of colic will turn out to be grass sickness.


Free veterinary advice helpline: 01243 773363 (UK)
Free veterinary advice helpline: 0044 1243 773363 (International)
Mobile veterinary advice line: 07734 240 709 (UK)

All numbers available 9am - 5.30pm UK time.
Out of hours: try mobile number.