This podcast discusses the various health risks that horses face during the spring season, including colic, laminitis, grass sickness, head shaking, atypical myopathy, and respiratory issues. Dr David Marlin emphasises the importance of gradual management changes, monitoring horse health, and consulting veterinarians when necessary. The conversation highlights the complex interplay between environmental factors and horse health, providing practical tips for horse owners to mitigate risks during this season.
There is lots of information on the Animalweb website to help and support you and your animals through Spring.
ARTICLE – Respiratory problems in horses: How to recognise, manage and avoid them
VIDEO – Spring Respiratory Issues
ARTICLE – Spring Associated Respiratory Disease is coming!
ARTICLE – Respiratory supplements for horses reviewed
ARTICLE – Mycotoxins – a hidden danger in your horse’s environment and feed?
Transcription
Here is a transcription of the podcast. (Please note this is an automated transcription, so we apologise for any errors from the original podcast.)
Hi and welcome to this Animalweb podcast about Spring with me, Dr David Marlin.
Well, we know spring’s here – there’s daffodils everywhere, we’re getting warmer weather and the grass is definitely growing. But spring isn’t always a great time for our horses. If I start reeling off colic, laminitis, sickness, head shaking, respiratory disease and atypical myopathy, you might be wondering – what’s going on in spring? Why can it be such a bad time for our horses’ health?
Let’s start with colic – that’s a fairly easy one. We see sudden lush grass growth and typically more turnout time. There are changes in grazing, possibly moving away from forage towards more fresh grass, and there are often higher parasite loads.
In addition, some studies have noticed that spasmodic colic in particular can peak in spring. One of the speculated causes is weather changes. Do they increase colic risk? The answer appears to be yes, though perhaps not for the reason you might expect.
If you’ve spent time around horses or on social media, you’ve likely seen the warnings – sudden changes in weather, temperature swings, storms, heavy rain – can upset a horse’s GI tract. It’s a common belief that weather shifts increase the risk of colic. Horses have very sensitive digestive systems that can be upset by relatively minor changes in their environment.
For years, owners and vets have debated whether these shifts actually impact gut health. There are theories, like changes in barometric pressure affecting gas in the large intestine. With storms come low pressure, which may allow gases in the hindgut to expand – potentially leading to gas colic or spasmodic colic.
Gas colic occurs when excessive gas builds up, causing painful bloating and discomfort. Spasmodic colic involves abdominal pain and intestinal spasms, often caused by gas, dehydration or parasites.
Let’s look at what some of the research tells us.
Cohen et al., in 1999, looked at 2,000 horses – half with colic, half with other emergencies – and linked colic with risk factors such as recent dietary or hay changes, history of colic, weather changes, recent changes in housing, recent or absent worming, older age (especially over 10), being Arabian, and being kept in stables rather than at pasture.
In 2006, Archer and colleagues in the UK studied 2,580 colic cases and found a seasonal pattern. Colic episodes increased when horses were more intensively managed – more stable time or significant management changes. The peak number of cases was seen in April and May.
A 2017 study from Greece reviewed 823 horses over three years. 245 developed colic. There was a statistically significant correlation between colic and abrupt 24-hour temperature changes – especially in late spring and autumn.
Curtis et al., in 2019, conducted a systematic review of studies relating to changes in feed or stabling and increased colic risk – a broader view rather than original research.
Cianci et al., in 2021, examined over 3,000 colic cases and found no direct link between barometric pressure and colic. However, colic incidence was higher in more northern regions and during spring, summer and autumn.
In 2023, Bhutan and colleagues in California reviewed over 3,000 emergency cases. These showed increased frequency on hotter days, during high barometric pressure, and with sudden pressure drops. While not all these cases were colic, the link between weather changes and equine emergencies is of interest.
So, overall, studies suggest that weather and seasonal changes likely play a role in colic risk – but it’s just one part of a complex puzzle. It’s not as simple as blaming the weather. More likely, it’s a combination of weather-triggered management changes, such as sudden shifts in stabling, turnout, feeding, and forage. Individual horse factors – like a prior history of colic – also matter.
So what can we do in practice?
The number one rule is to make management changes gradually. These are likely the biggest contributor to colic risk in spring. Whether you’re adjusting feed, forage, exercise, turnout or stabling – do it slowly. Watch out for sudden grass growth and introduce grazing gradually. Limit grazing time on new growth.
If you’ve got lush grass and horses or ponies at risk, consider a grazing muzzle. We’ve got some great information and recommendations on grazing muzzles – follow the link below this podcast for more.
Bottom line: abrupt changes in management are a known, significant risk factor for colic – so don’t do them.
Support your horse’s hydration. Ensure constant access to fresh, good quality water. Adding salt – around 50g (a 125ml scoop of table salt) per day for a 500kg horse – can help increase water intake and reduce the risk of impaction colic. You can also feed high water-content forage like haylage, soaked hay, steamed hay, or provide wetted feeds – all of which help.
Make sure you’re on an effective worming programme. We’ve got great expert content on worming – check the links under this podcast to learn more.
And remember – colic is serious and can progress quickly. If in doubt, consult your vet sooner rather than later.
So, to sum up: keep it simple, manage each horse as an individual, and remember that management – more than weather – is likely the biggest risk factor for colic.
Moving on – laminitis. Spring brings the highest risk of laminitis of the entire year. The main trigger is new spring grass, which is high in non-structural carbohydrates – simple sugars like glucose, fructose, fructans and starch.
Horses with EMS, Cushing’s (PPID), and those that are overweight are at highest risk. So what can you do? Limit time on fresh grass. Restrict grass intake. Use a grazing muzzle if needed – it’s not ideal, but it’s much better than an episode of laminitis. Again, visit our website for plenty of useful resources on this.
Let’s talk about grass sickness – also known as equine dysautonomia. Risk increases in April, peaking in May and June, but cases can occur into July. The main risk factors include increased turnout, more grazing time, and rapid grass growth. Possibly soil temperature and moisture play a part too.
Grass sickness is very rarely seen in horses fed only preserved forage. It’s linked strongly to fresh pasture.
Historically, it was thought to be caused by ingestion of Clostridium botulinum toxin. But recent research suggests a different culprit – a toxin called neurotoxic phospholipase A2. This toxin also occurs in the venom of snakes like cobras and rattlesnakes. It blocks nerve signals, especially at the neuromuscular junction, causing breakdown of cell membranes, paralysis, and eventually death.
Certain Clostridium species may produce similar toxins or mimic these effects – and this is part of what researchers are currently exploring in grass sickness.
In fact, a paper was published this January in the Equine Veterinary Journal by the Royal (Dick) School of Veterinary Studies in Edinburgh. It’s titled Neurotoxic Phospholipase A2: A Proposed Cause of Equine Grass Sickness and Other Equine Dysautonomias (Multiple System Neuropathies). So we are making real progress here – and hopefully heading towards a vaccine or better treatments.
Another spring issue – head shaking. Many horses with a history of trigeminal-mediated head shaking show increased symptoms in spring. Factors may include stronger sunlight, increased temperature and changes in air quality.
Along with colleagues Veronica Roberts (Bristol), Kirsty Pickles (UCLan Vet School) and Jane Williams (Hartpury), I recently published a paper using head-mounted sensors to track headshaking intensity and frequency. It’s a breakthrough – helping us understand the condition, identify triggers, and objectively measure treatment outcomes.
Head shaking can be periodic. Some days it’s severe, some days it’s not present. That’s why continuous, objective monitoring is so important. Check the links for some excellent content by Dr Kirsty Pickles – a recognised internal medicine veterinary specialist and one of the leading experts in equine head shaking.
Two more conditions to highlight.
Atypical myopathy – a very nasty disease. It’s caused by ingestion of hypoglycin A, a toxin found in sycamore seeds. Specifically, Acer pseudoplatanus, not to be confused with other types of sycamore.
The peak seasons are autumn, when seeds fall, and spring, when seeds germinate. Again, check our Animalweb website for content on how to manage this, spot symptoms, and learn about current research.
Lastly – respiratory health.
Many horses start to show symptoms like nasal discharge or coughing in spring. Reasons include higher pollen levels (from trees, grasses, weeds), and increased mould spores. Respiratory infections – such as herpes virus, flu, and strangles – can also become more common with increased travel and show attendance.
Some people worm their horses in spring, and this can occasionally cause parasite migration leading to respiratory signs – although this is less common.
Key message – healthy horses should not cough. Even the occasional cough while warming up, or in the stable, isn’t normal. Always consult your vet.
Unlike humans, horses with respiratory disease often don’t cough – so absence of coughing doesn’t mean they’re fine. The only way to be sure of respiratory health is to have your horse scoped. Many scoped horses show high levels of mucus in the trachea, even when they show no outward signs.
So when horses do cough, it should always be taken seriously. Bottom line – healthy horses don’t cough. Sick horses may – or may not.
To summarise – while we all look forward to spring and better weather, it’s important to remember it’s one of the highest risk times of year for our horses. Possibly even the riskiest.
If you enjoyed this podcast and want to learn more, visit the Animalweb website or follow the links below. We’ve got a huge amount of content from world-class contributors – actual experts in their fields.
Cheerio.
