Although we often think that all laminitis is ‘inflammatory’, there are two other kinds of pathology that can start the process of tissue deterioration within the hoof. Laminitis is therefore classed as either ‘inflammatory’, ‘metabolic’ or ‘overload’. In the second of a two-part look at this debilitating condition, Sarah Hogg BA VetMB MRCVS from Paragon Equine explains...
It’s important to pinpoint what type of laminitis is occurring in order to develop a specific treatment plan that will help your horse get back to full health as quickly as possible, and to minimise the chances of recurrence in the future.
This is the commonest and possibly the most confusing type of laminitis. Vets have estimated that more than 90% of horses presenting with laminitis as their primary (main) complaint are metabolic cases. There are two underlying conditions involved in metabolic laminitis:
· Equine Metabolic Syndrome (EMS)
· Cushing’s Disease (more correctly called Pituitary Pars Intermedia Dysfunction; PPID).
Both conditions mean that horses have an inappropriate response to eating carbohydrate rich food (grass, concentrate feeds, hay and haylage) and produce too much insulin. Because of these high levels or unusually large spikes in insulin, the body becomes less sensitive to it. This is called ‘insulin resistance’.
Equine Metabolic Syndrome
EMS is a complex condition responsible for most cases of metabolic laminitis. It usually affects native pony breeds. Although it’s still unclear exactly how EMS causes laminitis, we think that high levels of insulin following carbohydrate digestion alter the blood vessels and blood supply to the hoof first of all. This then causes an inflammatory response and clinical symptoms. Studies have suggested that many horses with EMS have had subclinical (grumbling) laminitis for a long time before they are diagnosed with it. They are also more likely to suffer from further episodes in the future, so it’s vital that EMS is properly managed to prevent this.
Obesity is known to exacerbate EMS. It can look quite different from how we think of obesity in humans or other animals, where we’d always expect an all-over covering of excess fat. In horses ‘regional obesity’, where fat builds up in just one or two areas such as the crest of the neck or behind the shoulders, can be just as dangerous. Body condition scoring is a uniform way for describing the weight of a horse compared to what their optimal weight would be (see box for more information on how to do this properly).
The good news is there are plenty of ways we can help reduce the effects of EMS. Early diagnosis and management is critical and your vet may suggest a blood test or glucose challenge test to help confirm EMS is present. Weight loss is central to treatment, and a plan should be made for decreasing the calories your pony takes in whilst increasing those burnt through exercise (once any laminitis has completely settled). Learn to body condition score your pony and use a weight tape regularly to record your progress.
The best diet for EMS ponies is hay that has been soaked for at least an hour to reduce soluble sugars, alongside a quality commercial feed balancer fed to replace any vitamins and minerals that are also washed away. Weighing your hay at each feed or sending a sample to a laboratory for nutritional analysis can help you to gain more informed control over your pony’s diet. Your vet will be able to help you decide on a suitable amount of hay to feed for successful weight loss without cutting down too severely. Once EMS is under control, it is often possible to return ponies to restricted grazing.
Metformin is a human medication used in type 2 diabetes that is sometimes used to help treat EMS in horses. Several supplements, from cinnamon to omega-3 fatty acids, have been scientifically tested but none have proved reliably effective so far.
PPID, more commonly known as Cushing’s disease, is a degenerative condition of the pituitary gland at the base of the brain that occurs as horses get older. A small area of the pituitary gland becomes hyperplastic (grows) or can develop a benign growth called an adenoma. It is a common condition, affecting around 20% of horses over 15 years of age.
Despite being small in size, the pituitary controls many hormonal processes throughout the body, primarily the ‘stress hormone’ cortisol. PPID can have a range of gradually progressive symptoms, including:
· Weight loss; or muscle wastage
· Characteristic fat storage: pot-belly, crest, supra-orbital fat pads (above the eye)
· Hirsuitism (thick, hairy coat) and delayed shedding of winter coat
· Increased drinking and urination
· Mouth ulcers
· Prone to infection (e.g. skin, hoof, respiratory)
Although a clinical exam can be strongly suggestive of PPID, your vet will usually confirm diagnosis with a blood test.
Pergolide is an oral drug that effectively stabilizes most horses with PPID and can help to prevent or reduce further flare-ups of laminitis. Careful dietary management and regular farriery are also key to successful management.
Inflammatory laminitis occurs after the onset of a severe illness. Toxins are produced as a byproduct of inflammation and tissue damage, and travel through the bloodstream to affect all areas of the body – including the hoof.
Severe colic is an example of this kind of illness – when the gut is damaged toxins are released and travel to the feet to cause inflammation and damage in the sensitive laminae which hold the hoof the bone. Eating a lot of concentrate feed can have the same effect. Other examples include mares retaining their placenta after foaling and sepsis, where a bacterial infection overwhelms the body.
When dealing with inflammatory laminitis it’s vital that the original condition is treated alongside dealing with symptoms in the feet. This often includes antimicrobial treatment and strong anti-inflammatories. In the acute (early) stage, ice can be applied to the feet to try and shut down the blood vessels (like when we have cold hands and our fingers go white) to stop further toxins being delivered to the laminae and causing more damage. If a horse is known to be at risk from laminitis and is suffering from a severe systemic illness, your vet may want ice to be applied as a preventative measure.
This is the least common form of laminitis, but it’s important to be aware of as the early stages can be hard to spot. Overload laminitis happens when a horse injures a limb and the leg on the other side is forced to compensate by bearing more weight. The increased load from their bodyweight causes mechanical damage to the laminae and the sensitive tissue again becomes painful and begins to break down.
Overload laminitis is best prevented and treated by supporting the weight-bearing limb. Vets are usually aware of this risk when treating severe lameness, and will help you to make the best possible plan for effective nursing and recovery.
Treatments directed at the foot itself, rather than the underlying cause, are also important. Strict rest, deep bedding, foot supports and suitable analgesia (painkillers) can all be important.
Corrective trimming is crucial in some cases, to get the foot realigned. If this is the case, radiographs (X-rays) can give your vet and farrier more information. Sometimes dramatic re-shaping of the foot is required, with the toe cut back and heel lowered. A good working relationship and open lines of communication between all those who care for your horse can make a real difference to the outcome. Once recovered, regular maintenance farriery should be a part of any laminitis-prone horse’s routine.
During the acute phase of laminitis, a low carbohydrate diet should be considered. Your vet will be able to advise you on this, and on a maintenance diet going forwards.
Finally, don’t be afraid to ask your vet for good recommendations on where you can learn more about laminitis and any underlying disease your horse may have. Most practices have detailed information sheets for owners or will happily point you in the direction of up-to-date online resource.
How to Body Condition Score your Horse
This is a great skill to have in your toolbox! Even if your horse doesn’t have laminitis it can be a useful way to evaluate the natural changes in condition we should see throughout the year (e.g. losing some weight each winter).
Try to score your horse every two weeks – taking a photo on your phone can help as a record of progress. Take particular note of fat at the neck crest, shoulders, tail head and covering the ribs, pelvis and backbone.
SCORE 0 – Emaciated
Sunken rump, angular pelvis, deep cavity under tail, skin tight across ribs and hips, sharp backbone, narrow neck base.
SCORE 1 – POOR
Prominent pelvis bones, sunken rump but some give in skin, deep cavity under tail, ribs easily visible, prominent backbone, narrow neck base.
SCORE 2 – MODERATE
Flat rump running down from backbone, slight cavity under tail, ribs just visible, backbone covered but easily felt, narrow but strong neck.
SCORE 3 – GOOD
Pelvis rounded and covered by fat but easily felt, ribs and backbone just covered but easily felt, no crest (except stallions), firm neck.
SCORE 4 – FAT
Dip along back of pelvis to tail, firm pressure required to feel pelvis and ribs, dip along backbone, wide, firm neck.
SCORE 5 – OBESE
Deep dip along back of pelvis, skin over rump distended, pelvis and ribs cannot be felt, deep dip along backbone, broad, flat back, marked crest with fold of fat.
To read the first part of this article click Laminitis (part1)