Equine gut health has, rightfully, become a hot topic in both conversation and research. With the gut microbiome influencing so many aspects of health and performance, supporting gut health is a great way to keep our horses healthy, happy, and performing at their best. However, many modern management practices can be detrimental to the stability and effectiveness of the gut microbiome. While we can’t change all of them, there are certainly steps we can take to minimise the impact of current feeding and management systems.
Equids are thought to have been roaming the earth for more than 55,000,000 years, slowly evolving over that time into the horses we know and love today. The earliest evidence of domesticated horses’ dates back about 5000 years ago, so they’ve been living alongside us for less than 0.01% of the total time they’ve been evolving. Relatively speaking, they haven’t had a lot of time to get used to the way we choose to keep and feed them!
Horses evolved to live in herds and graze on a wide variety of different plant species, often including shrubs, bark and wild berries. This natural diet provided constant access to forage, a diverse mix of fibres, and beneficial plant compounds such as polyphenols. Stress also has a huge impact on the gut microbiota and was generally triggered by predators approaching. The hormone cascade involved in the stress response was a short, sharp event and the horse could relax again afterwards.
Most horses today are kept under very different conditions, with far fewer species of plants available to graze on, micro-stress on an almost daily basis and starchy cereal feeds. These factors contribute to the disruption of the gut microbiome and can increase the risk of adverse events such as colic and ulcers. Management strategies such as limiting stabling, turnout with other horses, consistent routines, planned exercise rest days, and routine maintenance including saddle fitting, dental check-ups, and hoof care all go a long way towards supporting gastro-intestinal health and the gut microbiome, but diet also plays a central role.
The gut microbiome is made up of a mix of bacteria, fungi, and even viruses, with the bacterial element being the most studied and understood. Within the bacteria there are thousands of different species, some of which are very beneficial for health, others less so. The most beneficial species thrive on fibre. By providing enough fibre to keep them well-fed and flourishing, the less beneficial species of bacteria are prevented from overgrowing. Research demonstrates that the higher the diversity of bacteria present in the horse’s hind gut, the greater the health benefits. As each species of bacteria seem to enjoy a different type of fibre, studies show that providing a range of different types of fibre encourages greater microbial diversity. “Fibre first” is a good motto when it comes to feeding any horse or pony, and super-fibres like sugar beet or alfafa beet are a great way to provide energy and gut-loving fibre benefits at the same time.
Some other ways to increase fibre types in the diet include:
- Allowing access to safe hedgerows while grazing.
- Sow wildflowers and herbs alongside grass in paddocks.
- Providing meadow hay rather than single species.
- Including plants such as oregano, rosemary, mint, thyme, nettle, Clivers, hawthorn and other hedge herbs in feed.
- Providing fruit and vegetable snacks such as carrots, parsnips, beetroot, turnips, celery, blackberries, apples, strawberries, melons and bananas.
Prebiotics are specific subsets of fibre known to nourish certain beneficial bacteria. While the science in horses is not yet advanced enough to link each prebiotic fibre to specific bacterial species or functions, these prebiotic fibres have consistently demonstrated a beneficial effect on the gut microbiota overall.
Probiotics are live bacteria and yeasts provided through the diet. Foals often provide themselves with probiotics naturally by eating their mother’s manure, called coprophagy. Soil-based organisms which act as probiotics are also ingested through grazing, usually the Bacillus strains, which are naturally present in healthy soil and therefore on grass. These bacteria are resistant to stomach acids and reach the hind gut alive. Probiotic yeasts can also be provided in supplement form, helping to maintain the balance of the gut microbiota in times of stress or dietary change.
The term Postbiotics refers to the compounds produced when beneficial micro-organisms in the hind gut ferment the fibre and prebiotics obtained through the diet. In a healthy, well-functioning and balanced hind gut these are produced naturally in abundance and include things like Short-Chain Fatty Acids (SCFA’s), also referred to as volatile fatty acids or VFA’s, which provide a vital energy source for the horse. B vitamins, vitamin K and amino acids are also synthesised by the beneficial micro-organisms including bacteria and yeasts. One such amino acid is tryptophan, which is required for the synthesis of serotonin either by the gut micro-organisms or the horse itself. This neurotransmitter is heavily implicated in mood regulation and is thought to be one of the reasons a healthy production of postbiotics or supplemental postbiotics in the diet may exert a calming effect through the gut: brain axis.
While this article focuses on the health of the hind gut and gut microbiota, concurrent strategies to maintain stomach health will also play into hind gut health, and vice versa. Management strategies reduce stress levels positively impact the gut microbiota but also lead to lower overall cortisol levels which reduces the risk of ulcers. Equally, maintaining a fibre-first approach to feeding with cereals only included where strictly necessary supports stomach health, but also lowers the risk of undigested starch moving through to the hind gut and feeding the unhelpful lactic-acid producing bacteria. Presence of stomach ulcers results in discomfort and stress, regardless of any other factor, which will then also impact on the hind gut. As such, thinking about stomach and hind gut together and strategies to promote health in both areas concurrently will produce better overall results than thinking of them as separate entities.
