When I was twelve I lost  my pony, Little Bracken, to the acute form of Equine Grass Sickness. He was a much loved pony with whom I had had much fun & success at local shows & events. Two days before he died we had both been enjoying a cross- country schooling session. The following morning we awoke to find him suffering from colic & despite very prompt & assiduous veterinary attention nothing could be done to relieve his suffering & we had to make the difficult decision to end his misery. 

Grass Sickness damages parts of the nervous system leading to paralysis of the gut & is believed to be caused by a toxin found in pasture. It is a major cause of mortality in horses, ponies & donkeys in the UK with more than 95% of cases proving fatal.