08/06/2026
Stressful Weaning & Long-Term Health in Young Horses
As a physiotherapist, I spend much of my time thinking about movement, biomechanics and physical health. But health and function donโt begin with muscles and joints alone. Early life experiences can influence the systems that underpin resilience, wellbeing and long-term health.
On what would have been my young horse Williamโs second birthday, Iโve been reflecting on weaning.
Weaning is something every foal goes throughโbut itโs not just a management step. For the foal, itโs a huge life event.
Theyโre not just leaving their mum. Theyโre losing:
โข their main source of comfort
โข their sense of safety
โข their routine
โข and a big part of their world overnight
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What happens in the body?
When weaning is sudden or stressful, the body goes into a stress response.
This can affect:
โข hormones (stress hormones like cortisol rise)
โข the gut (which is very sensitive to stress)
โข the immune system
Inside the gut, this may lead to:
โข an imbalance of healthy bacteria
โข a more โleakyโ gut lining
โข the immune system becoming more reactive than normal
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Do most foals recover?
Yesโmost foals settle, adapt, and go on to be absolutely fine.
But some donโt fully โbounce backโ in the same way.
You might notice:
โข they become quieter or more withdrawn
โข less playful than before
โข more likely to stand alone rather than engage
This doesnโt mean theyโre unhappyโbut it can mean their stress system has adapted to cope.
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Why this can matter later
Thereโs something called the gutโbrainโimmune connection.
In simple terms:
โข stress affects the gut
โข the gut affects the immune system
โข and all three influence each other
So if a horse has a difficult early experience, it may:
โข make their gut more sensitive
โข make their immune system more reactive
โข reduce how well they cope with future challenges
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The โtwo-hitโ idea
Many vets now think some illnesses develop in stages:
1๏ธโฃ An early stress (like difficult weaning)
2๏ธโฃ A later challenge (illness, parasites, stress, surgery, etc.)
For most horses, this isnโt a problem.
But for a few more sensitive individuals, these layers can build up and make it harder for their body to stay balanced.
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Important to say
This is not about blame.
โข Many horses are weaned in different ways and do completely fine
โข Stress alone does not cause serious illness
โข Every case is complex and involves many factors
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Why this matters
Itโs simply a reminder that:
โข early experiences shape young horses more than we sometimes realise
โข calm, gradual, well-supported weaning can make a difference
โข and behaviour changes can sometimes reflect deeper physiologyโnot just personality
Research consistently shows that:
โข Weaning is a significant stress event in young horses
โข Stress can influence the gut microbiome and immune system
โข Early life is an important period for developing long-term physiological resilience
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A personal note ๐ค
Weaning is something Iโve come to understand more deeply since losing William. William made me think not just about how horses move and function physically, but how their early emotional and physiological experiences may shape their health over time.
He was the most affectionate, gentle soulโfull of curiosity and joy as a foal. After a difficult weaning, he changed. He became quieter, more watchful, but always incredibly kind.
He later became unwell, and although his illness was complex and cannot be put down to any one cause, his journey has shaped how I think about early-life stress, behaviour, and long-term health.
He taught me more than I could ever have taught him.
And for that, I will always be grateful.
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Sources & further reading:
โข Mach N. et al. (2017) โ Early-life stress and weaning influence the gut microbiota in foals
โข Delank K. et al. (2023) โ Behavioural and physiological stress responses in weaned foals
โข Review: Weaning practices and stress in domestic horses
โข Review: The equine gut microbiome and its role in health and disease
โข Review: Early-life microbial colonisation and immune development in foals
