Sometimes, what seems the most basic of questions takes us down a rabbit hole of thought and contemplation! I’ve recently been trying to come up with a definition for ‘good health’, which is harder than it sounds, especially when we try to apply it to the microbiota in the horse’s gut. My first conclusion was “the absence of disease”, which is really what we’re looking for when we’re monitoring our horses on a day-to-day basis. The more I’ve been thinking about it, though, and having read some recent publications, the more that doesn’t quite cut it.
Should we be content that if we can’t see signs of any issues right now, we can say our horses are healthy? As a practitioner, I am thinking about the longer term when I evaluate a horse or pony in front of me. I am trying to keep horses and ponies in good health, which is why, if I am asked to make recommendations for an overweight horse, I will be starting them on a weight loss plan even if they haven’t had laminitis yet. Unfortunately, humans are not the best species at taking action before disease strikes. Whether it’s laminitis or a heart attack, people tend to need a life-changing event to occur before they change what they’re doing. Tamsin Furtado politely describes this phenomenon as needing an ‘awakening event’ which might also be referred to as a wake-up call!
In this scenario, the obesity is visible even if we can’t necessarily see the effect it is having on the endocrine system straight away, but what about the other things we can’t see? Is a horse in good health, for example, if there is dysbiosis in the gut microbiota that hasn’t caused the host an obvious clinical issue? What if I add “yet” to that question?
Research and collaboration
My journey down the rabbit hole of this conundrum started when I began collaborating with the Equine Grass Sickness (EGS) research group at Moredun. No causal organism or agent has been identified, and there is a sense that we’re looking for ‘a needle in a haystack’ or perhaps a paddock…(sorry!). When you consider the number of different micro-organisms, both bacteria and fungi that we know exist, and add to that the different mycotoxins, which are known to be in their thousands, we get a sense of how enormous a task it is to identify what causes this devastating disease.
The area that I am particularly interested in, and this is why it relates to the conundrum of what is good health, is why one animal in a group fed and managed in exactly the same way succumbs to EGS, and the others don’t. I have personal experience of this – more than 30 years ago now – but one Suffolk Punch gelding in our group in the same field and fed the same feed, forage, etc, died, and his mother and half sisters didn’t.
In discussions with the Moredun team, we have talked about how changes to the health of the gut could predispose some individuals sufficiently so that commensal organisms – those normally present in the gut – have the potential to be harmful. Interestingly, this was a key point drawn out from a workshop on another poorly understood disease in the horse, acute colitis. The name given to these organisms in the workshop report is pathobionts, and they are described as “innocuous to the host under normal conditions but appear to activate the immune system, leading to inflammatory diseases under the right circumstances”.
Pathobionts present a really difficult research challenge – if they’re always or often present, how do you know when they might become harmful? They also really challenge our thinking around what is good health! If they are normally present, should we consider them part of a ‘healthy microbiota’? Or is a ‘normal microbiota’ a more accurate and better term, and we just have to work to keep them in abeyance?
What can we do?
And that leads us to what we can do as horse owners. We have to try to prevent conditions from becoming just right for pathogens to take over, and, for me, there are two key things we have to try to do if we want to sustain that good health status.
The first is to provide a diet that is sympathetic to the horse’s digestive tract. What does that look like? Well, it’s one that allows the horse to eat for prolonged periods of time so that lots of saliva is produced, providing slow-release energy and has a balance of essential nutrients to build and repair tissues. Essentially, it is a diet that is high in fibre.
The second requirement is much harder to achieve, and that is to minimise stress. Somewhat inevitably, the things we want to do with horses ultimately causes them stress to some degree, but how we manage that and how we minimise the stress that we can do something about is key. And this means finding what works for each individual.
Having worked as a nutritionist for more than 25 years now, and the more I work with clinical cases, the more apparent it is that horses do not read the rule book and what is often missing in the management of these issues is an evaluation of this specific horse with its own unique set of clinical history. So, with this in mind, my revised definition of good health is ‘the absence of disease in a horse that is fed and managed in a way that is likely to mean they remain in good health’. It’s not the most succinct, but it encapsulates what I am trying to achieve when giving advice and making recommendations. What do you think?
Glossary
- Commensal bacteria – types of bacteria that live on or within a host organism in a manner where the host is not harmed.
- Colitis – inflammation of the colon
- Dysbiosis – an imbalance of microorganisms within a microbiome
- Pathobionts – species of resident bacteria, which are part of the host-microbiota, that have pathogenic potential
References, Reading and Links
- Tamsin Furtado – Exploring horse owners’ understanding of obese body condition and weight management in UK leisure horses – Furtado – 2021 – Equine Veterinary Journal – Wiley Online Library
- Equine Grass Sickness | Moredun
- Science-in-brief: Report on the 2nd Dorothy Russell Havemeyer Foundation workshop on acute colitis of the adult horse. Equine Veterinary Journal. Science‐in‐brief: Report on the 2nd Dorothy Russell Havemeyer Foundation workshop on acute colitis of the adult horse – Arroyo – 2025 – Equine Veterinary Journal – Wiley Online Library
