Equine Grass Sickness (EGS) is a disease that affects parts of the nervous system of horses. The majority of clinical signs associated with EGS are due to damage of the autonomic nervous system which controls functions such as breathing, heart rate and gastrointestinal motility which results in the main symptom of gut paralysis.
What causes the disease?
The cause of the disease is still unknown but the vast majority of cases of EGS occur in horses with access to grass. Recent research has shown links between the disease and a toxin producing bacteria, Clostridium botulinum, that is commonly found in soil. This bacteria can be consumed by the horse when grazing on affected land. Further research is being conducted by The Equine Grass Sickness Fund and others into the role this bacteria may play in causing grass sickness.
Where does it occur and what type of horses are at risk?
EGS occurs in most areas of England, Wales and Scotland and was first recognised during an outbreak in 1907. Great Britain has the highest number of cases in the world and horses in the eastern counties of England and Scotland are at a greater risk of EGS. It is well recognised that certain yards and even fields within yards are associated with the occurrence of EGS. Some recent evidence has suggested that a high nitrogen content of the soil and recent soil disturbance may be risk factors for the disease.
Cases are reported throughout the year, but the disease is most prevalent in the spring between April and July. EGS can affect horses of all ages but the greatest number of cases occur in horses between 2 and 7 years old.
How does EGS affect the horse?
EGS affects horses in three forms: acute, subacute and chronic with acute being the most severe. Sadly horses diagnosed with chronic cases of EGS are the only horses that have the potential to survive and despite every effort, the disease is often fatal. Symptoms of EGS include reduced mobility of the bowel due to gut paralysis leading to colic, lack of appetite and difficulty swallowing and eating. If grass sickness is suspected a vet should be called immediately for diagnosis.
Feeding a horse with EGS
Horses with chronic grass sickness should be provided with highly palatable and easily digestible food such as high energy concentrate feed and chopped vegetables. It is essential that these horses consume a high energy and protein diet to encourage weight gain to restore the weight that has been lost due to the disease.
Pelleted feeds that can be soaked to a mash are useful as they can be soaked to the consistency that the horse prefers and are easy for the horse to consume and digest. Chaff type feeds are a good source of roughage, palatable and are easy to chew which is beneficial when horses cannot manage hay. Oil can be added to their feed to increase the energy content of their diet. It is also recommended to feed prebiotics and probiotics to support the beneficial bacteria in the hindgut and help to restore the correct microflora. Pre and probiotics can be found in many feeds and gut supplements. Fresh water should be available at all times.
Most feed companies will be happy to provide samples of a range of their feeds that are suitable for horses with EGS as it is often trial and error to find a feed that takes a horse’s fancy.
Equine Grass Sickness Awareness Week
The first Equine Grass Sickness Awareness Week runs from 29th March to 4th April 2021 with the aim to spread information and advice on this horrible disease. Check out Equine Grass Sickness Awareness Week for more information, details of new research and success stories of horses that have recovered from EGS.