Feeding the Horse with Equine Grass Sickness

Equine Grass Sickness is a disease of horses, ponies and donkeys which causes damage to the nervous system, resulting in paralysis of the gut. Equine grass sickness cases have been reported across the UK and can occur throughout the year although the most common period is between April and July, with a peak in May.

What Causes Grass Sickness in Horses?

The exact cause of equine grass sickness is still not known, but there is some indication that Clostridium botulinum may be involved. There is also a suggestion that a selenium deficiency may be a contributing factor. Selenium is integral to the horse’s immune defences and so a shortfall may make a particular horse more susceptible. Do be aware that selenium can easily be over-supplied which can also cause harm so additional selenium should be added to the ration with care.

Equine Grass Sickness Clinical Signs:

There are three forms of equine grass sickness – acute, subacute and chronic – with the acute form being most severe.

  • Acute grass sickness – horses display signs of colic as they are affected by complete gut paralysis. Other clinical signs of acute grass sickness include muscle tremors and inability to eat.
  • Subacute grass sickness – horses display clinical signs similar to acute grass sickness but with less severity
  • Chronic grass sickness – Chronic grass sickness in horses can appear as severe and rapid weight loss and a select portion of these cases may survive

The clinical signs of equine grass sickness can be obvious, but diagnosis and a comprehensive treatment plan for grass sickness requires veterinary attention.

Feeding the horse with Equine Grass Sickness

The main aim is to use feeds that are easy to chew, highly digestible and palatable to the horse. It may be necessary to try a variety of different feeds to see which appeals to the horse. Turning the feed into a slurry or gruel that the horse can drink often helps and so feeds that lend themselves to this are ideal:

  • Mashes are designed to be fed soaked so tend to contain small particle sizes. A greater proportion of water can be used to make their consistency thinner. Dengie Alfa-Beet is ideal for supplying highly digestible fibre that is easy to eat.
  • Pelleted feeds have a small particle size as they have been ground before being turned into a pellet. Water can be added to make them into a gruel. Dengie Pure Grass Pellets contain pure dried grass. Grass is naturally sweet which can help to tempt horses to eat.
  • A cooked cereal meal can also be a useful way of supplying lots of highly digestible energy in an easy-to-chew-and-swallow form.

If the horse’s appetite starts to increase then the aim is to increase the energy and protein levels in the feed to try and restore the weight and condition that has inevitably been lost as a result of Equine Grass Sickness. A phenomenon called refeeding syndrome exists whereby if too much is fed too soon, a rapid rise in blood glucose and associated surge in insulin ensues. The insulin drives glucose and potassium into cells which also utilises other minerals and electrolytes. These are depleted because of the horse’s illness and so the sudden shift away from other functions can cause organs to fail – most commonly kidney, lungs and the heart. The most common time for this to occur is 3 to 7 days after refeeding starts.

Independent research from the US has shown that one way to reduce the risk of refeeding syndrome is to use alfalfa as it is low in starch and so doesn’t cause the increase in glucose and insulin associated with feeding cereals, but is also relatively abundant in minerals such as potassium, magnesium and calcium. It also provides good levels of quality protein to support the horse’s recovery. Although not included in the study, the same can be said of unmolassed sugar beet pulp which is also low in starch and sugar and contains a valuable level of calcium.

Using a digestive supplement is also recommended. A prolonged period of little or no forage intake will have caused a disruption to the population of micro-organisms in the digestive tract. Using a digestive aid to try to help establish a healthy population is key. Live yeast is an approved additive for horses and has been shown to improve fibre digestion.

Using scFOS prebiotics may also be beneficial. They provide a food source for beneficial species of bacteria which helps them to proliferate and out-compete harmful species; a process known as competitive exclusion. There have been studies in humans to show that scFOS prebiotics are particularly effective at reducing the presence of clostridium species.

The Importance of a Balanced Diet for a Horse with Equine Grass Sickness

As mentioned earlier, a deficiency of selenium has been associated with potentially making horses more susceptible to Equine Grass Sickness. The key is therefore to ensure that a horse’s requirements are met but there is no evidence to show that feeding excessively high amounts of selenium will have any protective effect against Equine Grass Sickness. The key principle is therefore to provide a balanced diet of all essential nutrients.

Good doers are the most likely to be deficient in micro-nutrients as they tend to be fed low levels of bucket feed which is the main source of trace minerals such as selenium for most horses. Forages reflect the soils they are grown on and as UK soils are very low in selenium, very little is supplied to the horse through the forage part of the ration. A low calorie source of vitamins and minerals is therefore recommended for good doers which can be supplied as a supplement or a balancer.

Generally speaking, horse’s receiving recommended feeding rates of fortified feeds or a broad spectrum supplement should receive sufficient levels of trace minerals. However, when horse feeds are formulated it is on the assumption they are fed alongside average quality forage. There may be occasions when selenium levels in forages are low even by UK standards and so additional supplementation may be advisable. If there is a history of Equine Grass Sickness where you keep your horse or pony then it is worth analysing your forage and asking a nutritionist to advise on suitable levels of a supplement or balancer to use to ensure sufficient selenium is provided in the diet.

Practical Advise for Trying to Reduce the Risk of Equine Grass Sickness

Sylvia OrmistonSylvia Ormiston is the Stud Manager at the Royal Stud at Balmoral and has sadly lost Highland ponies to EGS. Very sadly two stallions were lost in a matter of weeks in 2018. Understandably, Sylvia does everything she practically can to reduce the risk of EGS and her management advice is as follows:

“Equine Grass Sickness is a devastating disease that is 80% fatal. I had never experienced EGS in all my years with horses until we had 5 acute, fatal cases in one year over 2017-2018” says Sylvia. “Having been affected so terribly I am determined to help raise awareness and fund raise to the best of my ability to assist with the eradication of this horrific disease.”

“I am a great believer in keeping something else in your pony’s tummy every day other than just grass especially during the early spring and summer months. I also have a low calorie mineral lick for the ponies to use 24/7 as the ground we graze on is very low in selenium.”

“It is recommended good practice to keep your equines off the pasture for a good chunk of the day which helps them to ingest some alternative form of forage. This is not easy in my case with around 45 ponies ranging from mares and foals to stallions and working ponies so I feed hay in the field to everyone every day. I believe in keeping the gut as healthy as possible by feeding a high fibre diet and avoiding sudden changes to the ration. Trying to reduce stress is general good practice and recommended; equines thrive on a consistent daily routine, as we all do.”

Highland Pony

“Be aware of your equines habits. Keep a close eye on their manner and performance as this can show as early warning signs to your pony’s well-being. Noticing if they haven’t done as many droppings or they aren’t eating as much is really important for catching problems early and having a better chance of a successful outcome. Little changes can set off big alarm bells for me having experienced EGS. Please do visit the Equine Grass Sickness Fund for more information on how you can help raise awareness and funds to help with the continuing research. Please help in any way you can and together we will beat this!! Thank you.”

Given the unique circumstances of Equine Grass Sickness we recommend contacting a nutritionist for advice and guidance for each horse as the amounts of each feed will vary considerably. However, when trying to tempt a horse to eat, the following products from the Dengie range are usually the most palatable and/or easiest to chew and swallow:

Alfa-Beet combines alfalfa with unmolassed sugar beet and is a highly digestible and easy to chew soaked feed.

Hi-Fi Senior combines alfalfa and soft grasses with a molasses and rape seed oil coating, making it highly digestible and easy to chew. Hi-Fi Senior can be fed ab lib as a total forage replacer if required. The short chop length makes it easier to chew than hay or haylage.

Healthy Tummy is a nutritionally balanced , high-calorie feed containing the latest ingredients known to promote gut health, including alfalfa. Healthy Tummy combines chopped and pelleted alfalfa with an oil coating, ADM Protein In-Feed Formula which contains scFOS prebiotics and a unique blend of herbs including oregano, cinnamon and ginger.

Alfalfa Pellets contains pure high temperature dried alfalfa and are an excellent way of providing fibre in a concentrated form. For example, 1 Stubbs scoop of Alfa-A Original holds 0.4kg whereas a Stubbs scoop of Alfalfa Pellets holds 1.6kg.

Pure Grass contains high temperature dried grasses in a short chop format that is easy to chew. Pure Grass is naturally sweet which can help to tempt fussy feeders and can be fed ad-lib to replace the usual forage ration.

Pure Grass Pellets are pure high temperature dried grass pellets with nothing else added. Grass is naturally sweet which helps to tempt fussy feeders. These should be soaked to a mash when fed alone.

Meadow Grass with Herbs combines chopped and pellets grasses with a rapeseed oil coating and herbal blend. Meadow Grass with Herbs is a high calorie feed that is soft and easy to chew and highly palatable due to the naturally sweet grass and additional herbs, perfect for the fussy eater.

For more information about any of our feeds don’t hesitate to contact our friendly Feedline team on 01621 841188.

Gibson et al (1995) Selective stimulation of bifidobacterial in the human colon by oligofructose and inulin. Gastroenterology. 108: 975-982
Witham And Stull (1998) Metabolic responses of chronically starved horses to refeeding with three isoenegetic diets. J Am Vet Med Assoc. 212: 691-696