Is Grass Really the Problem? Looking Beyond Grass Sensitivity in Horses
Grass sensitivity is something we hear about increasingly often. Horses become footy when they go onto grass, their behaviour or comfort changes, or they have a history of laminitis and suddenly grass becomes something to fear and avoid.
For some horses, restricting grass is absolutely necessary, particularly where there is active laminitis, insulin dysregulation or significant metabolic dysfunction. Grass-free tracks and turnout areas can provide an incredibly useful environment in which to stabilise a horse and allow recovery to begin.
But I think we need to be careful about assuming that because removing grass removes the symptom, we have also identified the root cause.
Grass may be the environmental trigger that exposes an existing vulnerability. The more interesting question is why one horse struggles to tolerate that trigger when another doesn't — or why the same horse's tolerance can change considerably over its lifetime.
This is where I think we need to look beyond grass and consider the chronic physiological state of the whole horse, including something rarely discussed in relation to metabolic health: hoof care.
What have the feet got to do with metabolism?
Potentially more than we realise. Metabolism doesn't operate independently of the rest of the body, and neither do the feet. The hoof is the interface between the horse and the ground. Its morphology influences loading, and loading influences how the horse stands and moves.
When hoof morphology becomes pathological, we can see changes in posture, movement, muscular recruitment, tissue loading and neuromuscular organisation. We can also see changes in comfort and in how much — and how well — the horse chooses to move.
This becomes particularly interesting when we consider the metabolically challenged horse. Skeletal muscle is metabolically important tissue, while physical activity, pain, stress, body composition and endocrine function all interact with metabolic regulation.
So perhaps a horse standing and moving within a chronically compensated posture because of its feet isn't experiencing a problem confined neatly below the fetlock.
The consequences may extend throughout the horse.
I've seen grass tolerance change when hoof care changes
This is where my own observations have made me increasingly curious.
I have worked with horses considered extremely grass sensitive, whose management had become progressively more restrictive because exposure to grass repeatedly appeared to cause problems.
We changed the hoof-care approach and addressed pathological hoof morphology. As the feet changed, we documented changes in loading, posture, movement, comfort and tissue development.
And in some of those horses, something else changed too.
Their apparent tolerance to grass improved — sometimes considerably.
The grass hadn't changed. What appeared to have changed was the horse's ability to cope with it.
Now, this doesn't demonstrate that changing hoof care directly “cures” metabolic dysfunction, and I wouldn't make that claim. But when we change one significant part of the horse's physical state, document wider changes throughout the horse and subsequently observe a change in its tolerance to an environmental challenge, I think we should be curious about the relationship.
There are several plausible mechanisms that may contribute. Improved comfort may encourage more spontaneous movement. Changes in posture and locomotion may alter muscular recruitment and physical activity. Reducing chronic pain and compensation may influence physiological stress. Changes in movement and muscle function may contribute to wider changes in metabolic health.
Several of these things may be happening together.
We don't yet understand the full relationship, but that shouldn't stop us documenting what happens and asking better questions.
Grass-free can be therapeutic without automatically meaning grass-free forever
Grass-free tracks and turnout can be incredibly valuable, and there are horses for whom long-term grass restriction will remain necessary. But I think there is an important difference between using an environment therapeutically and automatically assuming that because a horse needed that environment during one stage of its recovery, it must remain there for life.
If the horse changes, surely we should continue to assess whether its tolerance changes too?
A grass-free environment can give us greater control while we address the things we can influence: diet, body condition, endocrine disease, comfortable exercise, hoof morphology, posture, movement and whatever else is relevant to that individual. Then we continue to observe the horse rather than simply following the management system.
This doesn't mean experimenting with unrestricted grass in a horse at significant risk of laminitis. It means recognising that today's tolerance doesn't necessarily represent that horse's permanent capacity.
Evidence over assumption in grass sensitivity in horses
This is one of the reasons I place so much importance on a welfare-focused and evidence-based approach to hoof care. Rather than deciding that a particular trim, management system or environment is right because we believe in it, we can look for evidence of what it is actually doing to the horse.
I tend to consider this through three interconnected welfare parameters: posture, physiology and behaviour.
Posture allows us to assess how the horse is organising and supporting its body and whether this changes following intervention. Physiology includes hoof morphology and tissue development, muscular development, movement and neuromuscular function, metabolism, homeostasis and evidence of pathology. Behaviour gives us another important window into welfare through comfort, willingness to move, interaction with the environment and the expression of normal behaviours.
The real value comes from documenting these things over time.
We can change the hoof-care approach and track what happens to hoof morphology and posture. We can observe changes in movement, comfort and behaviour. We can use metabolic or veterinary markers where appropriate, and we can document the horse's response as diet, exercise, grass exposure and other environmental variables change.
That allows management to become individualised rather than ideological. We intervene, observe the evidence and reassess.
If welfare parameters improve, that supports what we're doing. If they deteriorate, we should be prepared to question the intervention and change it. Most importantly, it makes us accountable to the horse rather than to a particular methodology.
Building resilience, not simply avoiding triggers
None of this means that every grass-sensitive horse should eventually live on unrestricted pasture. Some won't, and shouldn't. Nor does hoof balance replace appropriate investigation and management of PPID, insulin dysregulation, laminitis or other pathology.
What I am questioning is our tendency to identify an environmental trigger and then stop looking. If a horse requires a grass-free environment while it heals, use it. If diet needs changing, change it. If endocrine pathology is present, identify and manage it.
But also look at the feet. Look at posture. Look at movement and tissue development. Look at the physical and behavioural state of the whole horse and continue collecting evidence as those things change. Because surely our aim should be more than creating an environment sufficiently restricted that symptoms don't appear.
Where possible, we should be creating the conditions that allow that individual horse to become more functional, more physiologically resilient and better able to cope with its environment over the long term.
Grass may be the thing that exposes the problem. That doesn't necessarily mean grass is the problem. And when we see a horse's tolerance to grass apparently change alongside measurable improvements in hoof morphology, posture, movement and wider welfare parameters, I think we should be sufficiently curious to ask why. That, for me, is what evidence-based hoof care is about: assessing posture, physiology and behaviour, tracking the effects of the interventions we impose and using that evidence to create the best possible environmental stimulus for long-term resilience, welfare and longevity.
Continue the conversation
At Holistic Equine, we explore hoof care within this wider welfare framework, using evidence from the whole horse rather than allegiance to a particular methodology.
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This article is intended for education and discussion rather than veterinary diagnosis or treatment. Where there are concerns about laminitis, endocrine disease or metabolic dysfunction, appropriate veterinary investigation should form part of the horse's professional care.
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Beccy Smith BSc ADAEP EBW
Diploma in Advanced Applied Equine Podiatry, Independent Integrative Equine Podiatrist, Consultant and Therapist. Certified Lazaris Nerve Release TM Practitioner and Wellness Coach for People and Horses
CEO and Founder of 100% Non-Profit Community Interest Company Holistic Reflections CIC
Holistic Reflections CIC – a 100% non-profit organisation promoting wellbeing and resilience in people, horses and the environment - for the benefit of all.
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