Managing Grass Sickness Risk Factors

Some thoughts on managing your horse to minimize the effect of Equine Grass Sickness risk factors. By Catriona M. Rowan, BHSAI, RDA Group instructor, Horse owner and breeder since 1966.

November 2007

The following are suggested strategies used by one owner to maximize Gut Flora Health and to minimize disruption whilst striving to maintain a healthy gastro-intestinal tract. Many of the identified increased risk factors for EGS involve a change in the horse’s circumstances which may, in turn, affect the animal’s general health.

Stress factors (unalterable)

1. Growth; 80% of EGS cases are 2-7 years old so this should be the main period of vigilance. 2. Changing coat in spring and autumn. 3. Coming into season for mares. 4. Adverse or extreme weather changes causing a check or flush in grass growth rates, the majority of which occur in spring and autumn when late or early frosts and sudden weather changes are most likely. Most cases of EGS occur in April or May with another peak in September/ October during some years. These weather events can cause rapid and significant changes in the mineral, fructan and carbohydrate content of the grass.

Stress factors (manageable)

1. Change of diet and worming 2. Change of social companions. 3. Change of grazing or stabling. 4. Change of routine (including attending shows and events ‘off-grass’). 5. Medication for any reason, particularly antibiotics, as they will affect the gut bacteria in most cases.

Strategy to minimize risk

Avoid multiple changes. Move one day then leave a period of 8 to 10 days before making a further change, for example, introducing additional new companions. All of the above could cause unseen stress in the horse which, possibly through an acidity change in the gut, might disrupt the numbers and efficacy of the Gut Flora.

Example: You acquire a new horse so you could move him to your yard, feeding him to his previous owner’s schedule. Take a dung sample to send for a worm count. Over the first days a pre/probiotic supplement can be introduced to be fed for the first 2 weeks or so. During the second week you could begin to introduce your feed and routine. Subsequently new companions can be put into his field (mildest mannered first to reduce bullying). Should the worm count indicate that worming is necessary try to do this during a period of mild, wet weather when the grass is likely to be stable in mineral content, i.e. No sudden changes in temperature are forecast.

Now, when I worm my horses, I add some pre/probiotics to the feed for around 10 days following treatment and I am especially careful to ensure that they have free access to a multi mineral lick (low in molasses) and a daily portion of seaweed (pre-soaked in 4 parts water to 1 part seaweed for increased absorption).A handful of grain can be added for palatability and fed most days during the grass growing season as that is when these variations in fodder quality can occur. The same would apply if your horse had to have veterinary treatment for any reason.

During winter, when the relatively more stable mineral content of the diet is contained in hay then it is not necessary to feed the seaweed more than once or twice a week, unless some other stress factor has been introduced into the horse’s life. Seaweed has been chosen because it contains a small amount of a vast array of different minerals, especially manganese, which is important for bone growth and to the gut flora for their nutrition. On the assumption that cut and dried forage has a more stable nutritive content than growing grass, then it would be sensible to feed hay during stress periods or to try to make significant changes to your horse’s environment whilst he is on a predominantly hay/haylage diet.

This routine has been employed on my premises since 2001, just after I lost my most recent of the 8 cases of EGS that I have suffered over 35 years. Instead of avoiding young horses and stress, I have tried to test out my theories on feeding the Gut Flora in order to maintain a healthy digestive process. To be simplistic: Healthy Gut Flora = Healthy immune system = Healthy horse.

The objective is to maintain whole gut health and integrity by thoughtful management of change and by striving to feed the all-important Gut Flora during periods of stress.

Interesting facts: One third of a horse’s dung is composed of discarded gut bacteria; this demonstrates forcibly how important these bacteria are in the digestive system. There are more microbial cells in the human body than there are human ones so horses could well be the same… they are vital and we should look after them! They have to be continually replenished or the digestive process grinds to a halt.