Fibre should be the largest part of our horses’ diet; the horse’s hind gut is filled with microbial populations designed to aid the digestion of these fibrous substrates. Let’s look at the role of these microbes, the different types found in the gut and how to maintain a healthy microbial “balance”.
The microbial population in the equine gastrointestinal tract is complex, consisting of bacteria, protozoa and fungi/yeasts. There are five main types found within the horse’s gut:
- Cellulolytic Bacteria, digest fibre to produce volatile fatty acids which is then converted into energy. They are the main bacteria found within the caecum and colon.
- Proteolytic Bacteria breaks down protein
- Lactic Acid – Producing Bacteria, digest starch and produce lactic acid as a by-product. A higher starch content in the diet will increase the lactic acid production from these bacteria.
- Protozoa produce volatile fatty acids
- Fungi/yeast help to break down fibrous substrates
The types of microbes present within the gastrointestinal tract will vary dependant on the feed types being feed, i.e. a high cereal diet may result in higher lactic acid – producing bacteria. The population will be individual to each horse, some horses can eat everything whilst others are more prone to digestive upsets.
What is a microbial unbalance and how can this affect our horses?
An unbalance is known as Dybiosis. To obtain a balanced population, the cellulolytic bacteria should be high and the lactic acid – producing bacteria low. A neutral pH level of the caecum and colon is favourable for the process of hind gut fermentation. However, a change in diet or increase in stress hormones, often seen in foals during weaning, can cause the lactic acid-producing bacteria to grow, increasing the pH level and resulting in an inhospitable environment for the cellulolytic bacteria. This increased acid environment increases the growth of pathogenic bacteria such as E.Coli, resulting in health issues.
What to look out for if your horse is suffering from Dybiosis
- Mild – Grumpy, tender to touch, depressed, decreased appetite.
- Severe- Diarrhoea, gassiness, colic or in extreme cases, laminitis
How to keep a healthy microbial balance?
Always supply an adequate amount of forage in the diet, as a guideline 1.5% of the horse’s body weight should be given in forage each day. A high fibre diet will encourage the growth of cellulolytic bacteria helping to maintain a balance.
Any changes to feed should be done gradually, it is recommended when changing feeds to do so over 2 weeks to allow time for the gastrointestinal tract to adapt. A sudden increase in starch could result in lower pH levels making the environment unfavourable for other bacteria.
Larger cereal meals should be divided into smaller more frequent meals if possible. By doing this you reduce the amount of cereals being digested at one time. Remember horses are trickle feeders, so feeding little and often is what they are designed to do.
New research is continually developing on the role of microbes within the horse’s gastrointestinal tract. The role of probiotics is becoming an increasingly used supplementation for horses suffering from digestive upsets. The use of anthelmintics can negatively influence the microbial population, targeted worming programmes reduce the amount of anthelmintics used helping to maintain a healthy balance.
Bluegrass Horse Feeds is an Irish horse feed producer based at its mill in Eglish in County Tyrone. Bluegrass Horse Feeds, which produces quality and innovative horse feeds, is the Ireland Team Member of Kentucky Equine Research. The Bluegrass Horse Feeds team works closely with owners, riders and trainers using the latest nutritional research and technology to achieve optimum performance from their horses. Bluegrass distributes its feeds the length and breadth of Ireland and has over 200 stockists. If you need nutritional advice please fill out our diet request form and while you're here find out your nearest stockist.
*K. Crandell.DR. (2010) Balancing the Microbes in the Horse's Digestive Tract. Kentucky Equine Research