The latest in mare health

 

This week, Horse and Hound did an article about what’s new regarding mare health. I found this a particularly interesting article and myself I have only ever owned mares. An interesting insight which I hope will enlighten me when in future looking out for my own horse.

Equine metabolic syndrome

The potentially disastrous consequences of uncontrolled equine metabolic syndrome (EMS) in pregnant mares were discussed by Dr Peter Morresey at last year’s American Association of Equine Practitioners convention.

Obese animals with EMS become insulin resistant and have altered levels of insulin and lipids in their blood. This can result in laminitis and even abortion in pregnant mares. Note that mares suffering from EMS before becoming pregnant are particularly at risk of high blood glucose levels due to insulin insensitivity.

Your vet can offer specific drugs that may be used to treat EMS. An owner can also reduce the risks to a pregnant mare suffering from the condition by limiting or prohibiting her access to hard feed and grass, while feeding a high-forage diet based on hay or haylage.

Exercise, as long as it is not prevented by laminitis, can also help control obesity. It is generally safe to exercise a mare until mid-pregnancy, but you should always discuss this with your vet first.

Promoting pre-natal health: Remember too that routine care should not be forgotten in the excitement of getting a mare pregnant and the impending birth. Attention to worm control, foot care and dentistry are all important if you want her foetus to remain well. A full dental examination by an experienced practitioner prior to breeding, or between foaling and rebreeding, will help promote a healthy pregnancy.

Reducing disease risk

Pregnant women are routinely tested for a range of diseases that might pregnant mareaffect their own health and that of their child. In mares, screening for infectious diseases should take place before the mare becomes in-foal.

Whether the mare is being covered naturally or by artificial insemination, it is important that both she and the stallion should first be tested by swabbing for the bacterial venereal diseases contagious equine metritis (CEM), klebsiella pneumoniae and oseudomonas aeroginosa. They should also be blood-tested for equine viral arteritis and infectious anaemia.

If any of the tests are positive, your vet will advise you the necessary treatment. Once the tests are clear, breeding may proceed. Your vet will recommend a suitable vaccination programme to protect your mare against infectious diseases during her pregnancy – including those that can cause abortion, such as equine herpes virus.

Management also has a large part to play. Minimise your mare’s risk of exposure to a disease by keeping her in a small group and around from young horses, those travelling or new yard arrivals.

Clues from the cervix?

Monitoring the cervices of pregnant women using ultrasonography is an accepted technique for predicting whether they may give birth prematurely. In mares, we know that failure of the cervical seal can cause pregnancy loss by allowing bacteria to track through the cervix and into the uterus before reaching the placenta. But ultrasonographical monitoring of mares’ cervices is not a common method of detecting these sorts of problems.

Traditionally, cervices have been assessed either by vaginal palpation or by using a speculum – techniques that run the risk of introducing infection. Palpation via the rectum is another option, but this is less accurate.

A recent study by researchers Dr Stefania Bucca and Ursula Fogarty has established the ultrasonographical appearance of the cervix at different stages of pregnancy in healthy mares. This research is significant because, once we know the standard appearance and measurements; we can use ultrasonography to identify abnormal changes to the cervix. A monitoring technique could then be developed to detect problems early on and to initiate treatment as early as possible.

Mares that have previously aborted due to placentitis – a (usually infectious) inflammation of the placenta – will benefit greatly from ultrasound monitoring of both the cervix and the combined uteroplacental unit during pregnancy. This monitoring will increase the chances of detecting and treating problems early and before external signs of infection, such as vulval discharge or premature mammary development, would have become apparent.

Watching her waistline

feedAn enormous amount of attention is devoted to what pregnant women should and shouldn’t eat and to suitable vitamin and mineral supplements, Undernutrition in pregnancy is known to have a detrimental effect on the health of the offspring in most species – including horses.

For most mares in the UK, however, there is probably a greater risk of owners overfeeding their mares. Because most of the foal’s growth occurs in the last third of a pregnancy, a mare’s nutritional requirements until that time do not differ significantly to those of a non-pregnant mare.

A 2012 study published in the veterinary record, by Van der Heyden et al, shows that nutrition during pregnancy has a significant effect on whether or not a foal develops osteochondrosis (OCD), which is a form of developmental oorthopaedic disease.

These study results should be interpreted with caution, because no data was available about the composition or the quantity of the foodstuffs being fed to the pregnant mares. But the overall conclusion supports the claims of previous research – that overfeeding mares during pregnancy is detrimental to the orthopaedic health of their offspring.

The message for the owners to take from this is that pregnant mares should have a high-forage duet supplemented by the correct balance of vitamins and minerals, which are available in commercial form from most of the large feed suppliers. She should not be overfed protein or starch, or be allowed to become overweight.

Pregnancy failure – should you try again

Even with the best care, pregnancy in loss rates in mares remains stubbornly high. Around 15% of pregnancies in UK mares confirmed at 15 days post-ovulation do not result in a live foal. For both emotional and financial reasons, many owners of mares who have suffered embryonic or foetal loss want to know whether it’s worth trying to breed again.mare and foal

Where the cause of pregnancy loss can be determined, the attending vet will be able to advise on whether it is likely to recur. In many cases, however, the exact cause and even the timing of embryonic loss remain unknown. This is partly because the loss is often only detected after it has occurred, but also because the mechanisms that cause it are not yet fully understood.

Research carried out last year in South Africa by Shulman et al established a ‘logistical regression model’. This takes into consideration data such as when the mare was foaled, her age and reproductive status, her incidence of early embryonic loss and the number of oestrous cycles in which she has been mated in a given year. This data can then be used to predict whether she is likely to become pregnant, and, if she does, the chances of carrying the foal to term.

Should this model prove applicable to larger mare populations, it may help owners in the future decide whether it is sensible to breed again from a mare.

 

 

What’s new in the veterinary world

Is osteochondrosis inherited?

Osteochondrosis (OCD) is a recognised joint disease in young horses. Several joints may be affected, but big hock joints such as the stifle and hock are commonly involved. Fragments or flakes of cartilage and bone become detached from the underlying bone, which usually causes swelling of the affected joint and often lameness. Keyhole surgery is often required to remove these fragments, or ‘chips’. If discovered early, the outlook is often good.

For a number of years, vets have recognised that there is a genetic hockcomponent to OCD development, in that the offspring of some stallions appear to suffer more than others. But this is not a straightforward inherited condition. Other factors such as growth rates, feeding, mineral intake, exercise and some management issues have a big influence.

In Norway, racing trotters are a mixture of either American or French trotter lines. Vets in Oslo examined X-rays from more than 1200 trotter yearlings and looked OCD in hocks and fetlocks, before tracing their pedigrees back to founder lines. This included examination of the breeding of more than 75000 horses.

They wondered whether either the French or American ancestors were more – or less – implicated in the inheritance of OCD and whether the cross-bred population benefitted more from mixed blood. The results showed that just over 16% of the hock joints X-rayed had signs of OCD and, combining all the fetlock joints from the yearlings, about 11% had chips.

Analysis of genetics and breeding revealed that development of hock and OCD appeared to have a greater genetic component than fetlock OCD. But there was no difference between the influences of French or American sires on the disease. The degree of mixing bloodlines made no difference – yearlings with greater diversity of genetic make-up had the same risk of OCD. While this confirms that the cause of the disease has many more factors than simply the breeding of the youngster, the influence of the immediate sire is still considered more important.

How does it affect show jumping performance?

OCD is common in young sport horses, especially warm bloods. After surgery, owners are often left wondering whether the horse will ever reach full potential. To try to shed some light on the subject, in recent years Belgian and Swedish vets have reviewed the performance of 215 stallions presented for admission as sires to the Royal Belgian Sport Horse Society stud book. The stallions had been X-rayed as youngsters and the prevalence of OCD was therefore known, but horses suffering significant lameness had not been admitted to the stud book.

The subsequent show jumping careers of the approved stallions were assessed for both the number of competitions entered and success in the ring. Overall, there was no difference between the stallions that had had OCD in early years and those that had not. But a closer look at the statistics revealed that performance was linked to the particular joint affected by the disease.

If the stallion had had OCD of one or both hocks as a youngster, both the number of competitions entered and the results appeared unaffected when compared with OCD- free stallions. Yet stallions with OCD of the front fetlock ended up going to fewer competitions in their careers. Those with OCD of the stifle appeared to have the lowest success results overall – they went to fewer competitions and achieved poorer results.

There were also individual stallions with OCD that had outstanding careers and statistical risk is not the same as a firm prognosis for an individual horse. The results appear to show, however, that we can be more confident about the outlook for youngsters with OCD of the hocks than those with the disease in fetlocks or stifles.

Testing tongue-ties

When horses fail to finish a race because of breathing difficulties, commentators and trainers often use phrases like ‘he’s swallowed his tongue’ or ‘he’s choked up’. This is semantics – horses cannot swallow their tongue, but they do suffer upper airway restrictions caused by a variety of problems, including difficulties with the soft palate and larynx.

tongue tieWhere this has happened, trainers frequently resort to the use of a tongue-tie – a strap or band of material that literally ties the tongue to the lower jaw beneath the bit. The tie can be made of leather, but it is often a piece of soft, elastic bandage or even a length cut from a pair of ladies nylon tights.

Racecourse vets will check that any tongue-tie used in a race is comfortable and properly applied before the horse races, but does it work? Does is improve breathing during strenuous exercise? Vets at Guelph University, Canada, used ultrasound scanners on 12 racing standardbreds to measure the position and alignment of the thin hyoid bones that support the larynx.

These bones loosely link the larynx to the base of the skull and to the back of the tongue by means muscle, ligament and cartilage. The arrangement is very mobile and moves backwards and forwards as the horse gallops and breathes. Three sets of data were measured while the horses were stationary; with no tack, with a full racing bridle and tack and finally with a tongue-tie applied.

The results showed that adding a tongue-tie alters the position of the hyoid bones and therefore of the larynx and base of the tongue. This does not prove that the airway is open, or that is improved, but it does reveal that the tongue-tie in its various guises has a definite effect on the anatomy of the throat.

Rolling before rising – part of the routine?

Animal behaviour scientists in Denmark have been studying the way in which horses get up on their feet after a period spent lying down. We’re all familiar with the tendency for horses to stretch after rising – the scientists suggested that this is a sign that horses are relaxed and not stressed by their environment.

They also discovered that the majority of horses observed had a roll of somerolling kind before getting up. If they had been lying upright, on their sternum, they either flopped on to their side or rolled on to their back before rising. If they were already flat-out, resting on their side, they either rolled on to their back or even right over before getting to their feet.

This pre-rising roll was fairly consistent. It made no difference whether the horses were stabled or in a paddock, but the stabled horses tended to be more careful and to roll on their side. Researchers concluded that this behaviour is another indication of a normal, relaxed horse who is happy with his surroundings. What we can learn is that we should expect our horses to roll before they rise 0 and that putting big horses in small stables or tying them in stalls limits their ability to relax in a natural way.

Mimicking nature

In the wild, horses move a lot and eat almost continuously. But we typically confine our horses, feed them concentrate meals two or three times a day and then wonder why they suffer metabolic problems associated with obesity and a sedentary lifestyle. Australian vets pondered this in relation to the bare summer paddocks of Queensland, where horses and ponies simply hang around the hay feeders.

horses in fieldThey devised a box-shaped hay feeder, which could open on two opposite sides to give access to the hair. When the motorised door on one side open, the other side closed automatically. Each side open for five minutes before switching over, which forced the horses to swap from side to side to get the hay. The vets fixed a 10m long fence to the feeder, sticking out into the paddock, which the horses had to walk around to access both sides.

Ten horses were shown how the feeder worked before being fitted with GPS tracking collars. In a series of experiments, some horses were kept in a paddock with an open feeder and others in the paddock with the automated version. The amount they moved around was recorded. In a 4hour period, the horses with the motorised feeder walked on average 630m compared to the 117m covered by those with the regular feeder. This proves that if the source of food is moved, horses will move to find it – as they would in the wild.

A Silent Killer – Cushing’s Disease

We all know that the cause of laminitis in the vast majority of cases is an underlying hormonal problem in the endocrine system. The two endocrine problems that leave a horse susceptible to laminitis are equine metabolic syndrome and Cushing’s disease. But which would you associate with Cushing’s disease – the elderly pony with the thick curly coat, or the international grand prix dressage horse in full training?

Australian dressage rider Brett Parbery knows to his cost that Cushing’s is not restricted to the equine OAP – he lost his Olympic hopeful Victory Salute to the disease in late 2011. He was only made aware of the presence of Cushing’s once the warm blood gelding developed severe and incurable laminitis. With recent research indicating the Cushing’s victory salutedisease can affect much younger horses than previously though, it’s important to be aware of its deadly potential and how it can affect your horse.

Cushing’s; what is it?

Cushing’s disease is called by the abnormal function of the pars intermedia part of the pituitary gland, which is situated at the base of the horse’s brain. The disease’s acronym – PPID – stands for pituitary pars intermedia dysfunction. In healthy horses, this part of the pituitary gland is under tight control. A horse’s age, however, this control starts to fail, so the gland enlarges and produces abnormal levels of several hormones in the blood stream.

Laminitis is one of the most devastating clinical signs of the disease and has significant consequences for the welfare of the affected horse or pony. Other PPID symptoms include excessive hair growth or abnormal hair growth patterns, such as a delayed shedding of the winter coat, and fatty tissue redistribution throughout the body. You should look out too for increased thirst and urination along with lethargy, sweating and a greater susceptibility to infection.

Exactly how PPID causes laminitis has yet to be clearly established, although researchers have demonstrated that high blood levels of insulin will cause laminitis in horses and ponies. Studies at Liphook Equine Hospital laboratory this year identified that PPID cases often have disproportionately high blood insulin levels in response to eating feeds containing glucose, when compared with healthy horses. It is suspected that high levels of insulin also occur when these horses graze pasture – which leads to an increased risk of laminitis.

A geriatric disease?

cushing's'When a horse shows some of the typical PPID symptoms, a vet may be able to make a presumptive diagnosis simply by discussing the horse’s history and performing a clinical examination. It is suspected, however, that PPID may result in laminitis well before other clinical signs are apparent. An additional blood test is often used to reach a definite diagnosis.

Adrenocorticotrophic hormone (ACTH) is one of several hormones produced in increased amounts from the abnormal pituitary gland in PPID- affected horses and ponies. We can measure ATCH levels in a simple blood test and a positive diagnosis is made when these rise above a certain point.

A study by Victoria Copas and Andy Durham last year at Liphook revealed that ACTH secretion can vary from month to month. There are higher levels in non-affected horses during the months of August, September and October. This means we use higher cut-offs for diagnosing PPID from August to October compared with November to July. In the case of a borderline result, vets may consider dynamic tests to confirm a diagnosis. The most common of these is the TRH stimulation test, which triggers the release of especially high levels of ACTH from the pituitary gland in PPID cases.

Since PPID is caused by age-related nerve degeneration, it follows that as a horse gets older the likelihood of a positive diagnosis increases. Originally, researchers though that the disease only affected geriatric horses. Until recently, there were few reports of PPID in horses under 10 years old and it was debatable whether to bother testing horses in this age group. The latest research has altered this point of view. Post-mortem examination of horse in the under-10 age bracket has revealed that some do indeed have PPID. As simple diagnostic tests have become available, younger horses with the most subtle symptoms have been tested and confirmed as positive. Testing for all laminitis cases fir PPID should therefore be considered – no matter what the horse’s age.

Reducing the laminitis risk

We know that many PPID cases are at risk from laminitis. This risk is persistent if the xraydisease is left uncontrolled, so the treatment is aimed at reducing both the chances of laminitis and the severity of the other associated clinical signs. The only medication licensed for the treatment of PPID in the UK is pergolide mesylate, otherwise known as Prascend. Pergolide inhibits the abnormal development of the pituitary gland, which may stop further enlargement of the abnormal tissue present and reduces the hormone levels that are subsequently produced.

Pergolide is considered a safe drug. The most common side effect is a loss of appetite when the treatment is started. This often resolves when pergolide is stopped and then restarted at a lower dose before being increased more gradually. Concerns that the pergolide may cause liver disease have been disproven.

There is some individual variation in the response to pergolide therapy. When obvious PPID signs such as lethargy, excessive hair growth and increased thirst and urination are resolved, we might assume that the disease is under control. But where the clinical signs are less defined, we cannot rely on the outward symptoms to judge if the pergolide dose is correct. In all cases, follow up blood tests will give a good indication of the drug’s efficacy. If the ACTH levels remain high, an increased dose may be necessary.

There is no evidence at this time that any herbal supplements can effectively control PPID. So what is the prognosis for a horse diagnosed with PPID? Unfortunately, the degenerative, age-related nature of the disease means that it can only be controlled rather than reversed. But with early and appropriate treatment, the horse may have many active years ahead.

The most likely cause of death in PPID cases is the development of laminitis, so survival is more likely if the disease is treated effectively and the laminitis risk is reduced. Studies have also revealed that PPID survival rates are lower if high levels of insulin are also present. What’s reassuring for horse owners is that high blood insulin levels can be controlled with diet management changes made under the guidance of the vet.

Unblocking the pipes

If you’ve ever suffered from sinusitis, you’ll know it can cause anything from a runny nose to rotten headaches and painful facial tenderness. Sinus disease can affect horses, too, with varying degrees of severity. Some cope well, whereas in others in can cause considerable discomfort.

The disease is poorly understood, yet it has significant consequences for welfare. It’s runny noseeasy to imagine than an affected horse could feel uncomfortable when tacked up and ridden, or experience pain when he puts his head down to graze. Sinus disease has been suggested as a possible reason for headshaking, poor performance and behavioural changes. This makes prompt diagnosis and effective treatment all the more important. But why does sinus disease develop – and how should we tackle the condition if it takes hold?

Understanding sinusitis

If a horse’s skull were made of solid bone, it would be too heavy to lift off the ground. Instead, several large, air-filled cavities – collectively called the Para nasal sinuses – make the head a more manageable weight so the horse can move at speed. These cavities are lined with mucous membranes that continually secrete mucus; this clear discharge drains naturally into the nasal cavity through small openings. When sinuses become inflamed, however, the normal secretions become thicker and the drainage system starts to block up. The discharge then becomes infected and pus collects in the sinuses, leading to sinusitis and a horse with a sore head.

In an attempt to better understand sinusitis disease, vets from the Edinburgh and Glasgow veterinary schools last year published one of the largest studies to date. Over a 12-year period, they reviewed 200 cases of equine sinusitis referred to the equine hospital at the University of Edinburgh. These were not straightforward and easily treated cases but more complex problems that were therefore more likely to require surgery. Tackling the different types of sinus disease has historically been fraught with difficultly, with many cases requiring prolonged or multiple treatments.

trephineBut the study revealed that the long-term success rates for treating the majority of these disorders have improved markedly over the past decade. Researchers found that 87% of cases had complete and long-term remission of all symptoms. A further 6% experienced partial remission – proof that treatment methods for equine sinus disease are now more effective.

Primary sinusitis is the most common of all the disease variations. Its exact cause remains unknown, but it is thought that a viral infection or a bacterial disease such as strangles can damage the lining of the sinuses and interfere with the normal clearance of mucus. This was the most common of the case studies in the Scottish veterinary school survey. Dental disease is the most common cause, affecting almost a quarter of cases in the study. Because the tooth roots extend into the maxillary (upper jaw) sinus, an infected or damaged tooth can also compromise the sinus, the resulting sinusitis can drag on for months, unless the affected tooth is removed.

Sinus cysts were responsible for 13% of the cases studied, followed by trauma from an injury to the head. Tumours, which accounted for 5% of cases reviewed, usually have the worst outcome, as some are inoperable. The two most unusual causes are fungal infections of the sinuses and haemorrhagic polyps, otherwise known as progressive ethmoid haematoma.

Clearing the airways

With multiple cases, each with a different prognosis it is important to establish exactly scopywhat is wrong. An endoscope is a vital tool for confirming that the discharge comes from the sinuses. Sinoscopy, where an endoscope is used to examine inside the sinuses, is even more effective, a tiny hole, known as a trephine, is drilled through the bone of the skull overlying the sinus so the endoscope can be inserted. This can be done in the conscious horses with the aid of local anaesthetic and is tolerated surprisingly well.

Sinoscopy is only an option if the sinuses are not already filled with mucous. Otherwise, they’ll need to be emptied first by lavage (flushing) or suction. An X-ray is useful even when there is fluid within the sinuses. It will reveal dental disease and soft tissue masses such as cysts or tumours. A bone scan may be necessary, however, to differentiate between dental and primary sinusitis.

Treatments will vary depending on the cause. Around 60% of human bacterial sinusitis cases resolve spontaneously without antibiotics. It is likely that many acute cases of equine primary sinusitis will also need no medication. But the longer the condition persists, the more serious the problem becomes.

diagramMucolytics, which dissolve thick mucus and old-fashioned inhalations, are still sometimes used to help shift muck and pus and restore the normal drainage mechanisms. Light exercise helps encourage the sinuses to clear. If initial treatment fails to clear the nasal discharge a more radical nasal treatment is sometimes required. Flushing the sinuses several times a day with large volumes of fluid is commonly performed via a tube placed in the sinus.

In chronic cases, more invasive and surgical techniques may be necessary to remove solidified discharge. The vet will usually create a bone flap in the skill to gain better access to the affected sinus. Enlarged drainage holes are sometimes opened up surgically, too, which works well in most cases with surprisingly little scarring.

In the future, more widespread use of advanced imaging techniques such as CT and MRI may further enhance sinus examination and allow more focused early management. It’s worth contacting your vet if a runny nose remains present for any length of time, especially if the discharge is just from one nostril.

Nosebleeds – when to take action

The sight of blood dripping from a horse’s nose can cause panic. But nosebleeds are a common problem and not necessarily something to worry about. Very occasionally, however, a nosebleed can be an early sign of something more sinister. While a minor, one-off bleed from one nostril may not warrant calling a vet, anything persistent or more frequent definitely requires investigation by a vet.

A common cause of nosebleeds is trauma, such as a bang to the head or from the nosebleedpassage of a stomach tube up one of the nostrils. Typically, a moderate amount of blood will be coming out of one nostril and the flow will stop of its own accord within an hour or so.

Other causes of bleeding from one nostril include nasal masses. These can range from small polyps to large tumours and tend to cause intermittent and moderate bleeds. The amount of blood will be less in the cause of an ethmoid haematoma, but these small bleeds may recur frequently over a long period of time.

Frequent bleeding from either one of the nostrils, or both, could point to a more serious underlying illness, such as thrombocytopaenia – a low level of platelets, which help the blood to clot. The amount of blood will be variably, with no particular pattern to occurrence or length of bleed.

Another possibility is exercise-induced pulmonary haemorrhage (EIPH). This can produce a variable amount of blood, usually out of both nostrils, after a significant period of exercise. The most useful diagnostic aid in investigating the cause of a nosebleed is endoscopy, which allows us to see where the blood is coming from. Video endoscopy, in which the image is seen on a screen, rather than down the more basic fibre optic scope, can often be done at a yard or clinic. Recent advantages in diagnostic imaging mean that we can now glean a huge amount of information from a CT scan, although this would be reserved for less obvious cases.

Emergency scenarios

nosebleed1A nosebleed rarely requires immediate veterinary action, but one emergency scenario is an arterial bleed. If an artery has ruptured, blood will not be trickling from the horse’s nostrils – it will be pumped out at an alarming rate. A blood loss of more than 30% can be fatal. For a 500kg horse, this would equate to about 15litres, or a full water bucket.

Up to this volume, most horses can cope with a relatively large loss of blood. Blood will be diverted to essential organs, the heart rate will increase and the horse will also have the urge to drink substantial amounts of water to compensate. An arterial haemorrhage can occur if the horse falls over backwards and hits his head. This can tear or detach the longus capitus muscles attached to the base of the skull, fracturing the basisphenoid bone. A more common cause of this type of bleed, however, is guttural pouch mycosis (GPM).

GPM is a fungal infection in the guttural pouches – air chambers situated in the neck just behind the skull 0 that are unique to the horse and whose function is not fully understood. In GPM, the fungus frequently grows on the wall of the internal carotid artery at the back of the guttural pouch. As it develops it eats into, and then right through, the artery wall. It’s important that owners are aware of GPM and that any substantial nosebleed is investigated promptly. What starts out as a relatively harmless –looking bleed can be an early indicator that a massive and potentially fatal haemorrhage is about to occur. Left untreated, the horse can bleed to death.

Immediate action is crucial

Endoscopy of the guttural pouches is usually adequate to diagnose GPM. Once diagnosed, the horse should be taken immediately to a specialist equine surgical facility for treatment.

There are a number of ways to prevent the bleeding. The most straightforward is to nosebleed2ligate or tie the internal carotoid artery. The anatomy of the circulation in the region of the guttural pouch, however, is very complex and occasionally bleeding can continue, despite ligation.

More complicated techniques include transarterial coil embolization, where a small coil is inserted into the artery to encourage the blood to clot, and balloon catheter embolization, where the same effect is achieved using a tiny expandable balloon. Both techniques require fluoroscopy – or real-time X-ray imaging – and the use of highly specialised equipment available at only a few specialist centres.

Time is very limited with GPM. The emergency of these cases means that ligation of the artery is usually the most effective and practical treatment. Ligating the blood supply causes the fungus to die – a process that is not guaranteed, yet seems to happen most of the time. We also treat it topically with antifungals administered via a catheter into the guttural pouches.

Treatment and check-ups may be on-going for some months. While prognosis is guarded, most successful surgery results in the horse making a full recovery. GPM may be dramatic and potentially fatal, but thankfully it is not common. It is not infectious to other horses and there are no known reasons why one horse contracts it and another doesn’t. The fungus is present everywhere. As far as we know, there is nothing that can be done to reduce the chances of a horse developing the condition.

Owners can, however, be vigilant to the treat by seeking immediate veterinary attention in the case of a substantial nosebleed. Early action could be a lifesaver.

Tapeworm – the enemy within

This week, Horse and Hound magazine looked at tapeworm in horses, coming up with some interesting developments of it over the past couple of years.

Once thought relatively benign, the tapeworm is now known to be a potential danger. Ofanoplocephala-perfoliata-egg-7616 the three tapeworm species affecting horses in the UK, the most common is Anoplocephala perfoliata. The pale-coloured parasite has a flat, segmented body and measures around 5-8cm in length once fully grown. Unlike other worms in the horse, the tapeworms develop inside an intermediate host – the microscopic forage mite. Horses become infected when they eat hay or grass containing these mites, which are themselves infected with tapeworm larvae. These then develop into adult tapeworms inside the horse’s intestines.

Once laden with eggs, segments of the tapeworm’s body detach and are passed out of the intestines in the horse’s droppings. The eggs are released into the pasture where ingested by forage mites. The life-cycle takes from three to six months to complete. Owing to our temperate climate, the UK’s horses are particularly susceptible to tapeworms. Some horses are more prone to infection than others. In fact, 80% of intestinal parasites reside within just 20% of the equine population. While young and geriatric horses are at greater risk from heavy burdens, tapeworms can lurk within any animal. What’s worrying is than an apparently healthy-looking horse can be harbouring a large build-up of these potentially lethal visitors.

Blocking the intestines

tapewormsfAdult tapeworms can be found at the narrow intersection between the small and large intestine called the ileocaecal junction. Here, they attach themselves in clusters to the mucosal lining of the digestive tract, using four suckers located on their head. If they build up in large numbers at this junction, tapeworms can cause inflammation that alters the movement of the intestines.

It is now known that infection with tapeworms is associated with an increased risk of colic, particularly spasmodic colic (a type I have experienced when my own horse got it at a competition – very worrying! ) or a blockage at this narrow junction known as ileal impaction. Another risk is intussusception, in which one portion of the gut telescopes into another and becomes stuck. Surgery is sometimes necessary.

Research at the University of Liverpool revealed that 80% of ileal impaction cases and 22% of spasmodic colic cases were due to tapeworms. Ensuring your horse is free of tapeworms will therefore reduce the risk of colic.

A ticking time-bomb

Testing for tapeworms can be tricky. Horses can have large tapeworm burdens and lifecycleappear healthy on the outside. Counting the tapeworm eggs in a faecal worm count (FWEC) is unreliable. Egg numbers are usually low and encased in the segmented tapeworm part rather than distributed evenly throughout the droppings. A negative result on a FWEC does not therefore mean your horse is free of tapeworm.

Instead of a FWEC, we can use a blood sample for infection, a method known as the ELISA or tapeworm antibody test. A horse with a high level of tapeworm infection will produce a large number of antibodies, which can be detected in the blood. The test indicates a broad level of intensity, rather than tapeworm numbers. The amount of antibodies will indicate whether the burden is low, medium or high.

While the blood test is useful for assessing whether your horse has been infected with tapeworms in the past, it is not a reliable indicator of response to treatment. This is because it takes around four to five months for the antibody levels to return to normal after the worms have been killed. Therefore the test only needs to be carried out once a year.

Horses with evidence of a high tapeworm burden on a blood sample are likely to be susceptible to infection with tapeworms in the future. The should be treated a second time that year, before being retested 12 months later.

Treatment options

horses-grazingThere are two different approaches to tackling tapeworm. Treatment can be targeted, following a blood test, or administered within an annual worming regime.

With targeted treatment, your vet will combine information on the horse’s worming history with FWEC and blood test results to decide whether he needs worming – and the most appropriate treatment if this is necessary. Targeted treatment can reduce the likelihood of worms becoming resistant to treatment and identifies horses at risk of high levels of worm infection. Using this method, horses are blood-tested for tapeworms once a year. Those with a high burden are treated after the test and then again six months later. The blood sample is then repeated the following year.

New horses on a yard should have a blood test or a FWEC, or be treated for both tapeworms and roundworms, before they are turned out with others. In some yards, targeted worming may not be suitable nor practical. In these instances, it is best to treat for tapeworms every six months.

Tapeworm infection is not linked strongly to seasonality, so the time of year that treatment takes place is not particularly important. A risk is higher after prolonged periods of grazing, however, it seems wise to treat at the end of a summer out at grass.

It is important to be aware that not all wormers kill tapeworms. The parasites can be treated with one of two drugs – praziquantel and pyrantel. The latter must be at a double dose. Fortunately, both drugs are very effective and cause death and detachment of the tapeworms from the gut wall within 24-48hr following treatment. They are available as single products or in combination with other drugs that target different types of worms. Parasite populations on the pasture  can be reduced by regular removal of droppings, resting grazing and rotating sheep and cattle on to horse fields.

To conclude, careful pasture management  combined with correct testing and treatment will ensure that tapeworm infection is controlled. For me, having moved around to different yards, I found it very interesting that not once were my horses, or new horses coming onto the yard I was at, were testing for tapeworm. Upon  moving, you are subject to the current worming cycle that yard operates on, meaning that if new incoming horses are infected with tapeworm, the chance of them spreading is increased if they are turned out immediately with other horses.

Hope you found this article interesting, more next week!

Overcoming a bad start in life

After going through the breeding process, nothing is better than seeing a proud mother foal birthwith her healthy foal. However, despite the best management, problems can and do occur. In the case of a weak or a wonky newborn, the race is on to nurse the foal through the crucial early days when the chances of survival can be slim. But if the initial – and often costly – treatment is successful, what about the future? Can an ill or injured foal become a sound athlete, or must a shaky start mean problems later in life?

Counting the cost

When making decisions about treating a sick foal, owners need to have some understanding of the long-term consequences of the disease or condition – especially in the current economic climate. Most research into the subject has focused on thoroughbreds and whether foals that have been sick in the early months of their lives are less likely to fulfill their potential on the racecourse.

A study carried out at Anglesey Lodge Equine in Co Kildare in 2010, however, took a slightly different tack. It sought to assess whether hospitalisation of thoroughbred foals in the first four months of life would adversely affect future sales performance. The study involved 63 foals, 53% of which were admitted to hospital in the first week of life with common conditions including diarrhoea, septic joints and pneumonia.

Of the group, 30% went to auction as foals, 62% as yearlings and the remainder were sold as two-year-olds. Their sale prices were compared with 378 control animals of similar pedigree going through the ring at the same time. The previously sick foals reached comparable sale prices to animals with no history of early sickness. This indicates that poorly foals are not necessarily disadvantaged in later life.

The study did not look at whether hospitalised foals were likely to reach public auction. We can glean some indication of the chances of a sickly foal fulfilling early potential from previous research carried out in the USA. Studies there revealed that 6% of foals formerly hospitalised remained unregistered following discharge, compared with a population average in the region of 1%.

Most studies involving breeds of all kinds look at even shorter-term outcomes – that is, whether the foal survives until hospital discharge. Few consider the long-term outlook for sport horses, as opposed to thoroughbreds. In part, this is due to the fact that most thoroughbreds are destined for the racecourse. Their history at sales and in racing can be traced easily through Weatherbys. For sport and pleasure horses, however, intended use is diverse and performance and sale results are not readily available. This makes obtaining reliable, objective long-term data much more difficult.

The critical early days

The first weeks of a horse’s life is considered to carry the highest risk of mortality. the newborn foal is susceptible to a range of potentially life-threatening diseases including septic arthritis (joint ill), septicaemia – often associated with inadequate ingestion of antibodies from the first rich milk or colostrum – and congenital conditions such as severe limb deformity. The bones of a foal can heal surprisingly well and early fractures do not necessarily limit the future performance. The outlook is much worse, however, when the fracture extends on to the weight-bearing area of a joint or infection damages the joint cartilage.

Septic arthritis and the bone infection osteomyelitis can carry long-term implications. While aggressive treatment early in the condition can significantly affect outcome, a UK study indicated that even a single infected joint can adversely affect the long-term athletic potential of racehorses.

Some diseases produce alarming symptoms, as in the case of perinatal asphyxia syndrome, which can cause problems such as convulsions, diarrhoea and an inability to stand and suckle. As long as the case is uncomplicated by infection, howeverm around 80% of foals affected are successfully discharged from hospital. The condition is though to have little impact on the foal’s long-term prospects.

A difficult decision

Foals are remarkably resilient, the downside being that health problems can be difficult to spot. The horse’s evolution as a prey species means that the foal – the most vulnerable member of the herd – will rarely show obvious signs of illness until a disease process is relatively advanced.

Vigilance is key. Long-term prospects are greatly improved if a problem is detected in its early stages and appropriate treatment started as soon as possible. As this can also influence the size of the vet bill, it pays to act immediately if something seems amiss.

Although advances in veterinary and surgical techniques are giving many of these foals better chances, a particular vet’s experience with foal problems can play a crucial role. More complicated cases tend to fare better at equine hospitals with experience staff, so an early referral will help.

Deciding whether or not to persevere with a sick foal is not easy, Treatment is often labour-intensive and costly, with the added risk of complications. Foals are rarely insured for vets’ fees and there are strict conditions for a mortality claim. Consider, too, whether you can provide the facilities for convalescent care, such as an exercise pen or nursery paddock, and specialised farriery or physiotherapy where necessary.

While there’s certainly potential for a poorly foal to grow up into a fit and healthy adult, its wise to know what’s involved before embarking on the journey.

 

Hope you enjoyed this article, I previously knew little about breeding so it was interesting for me to look into. More next week 🙂

What’s new in the veterinary world

In this weeks Horse and Hound, the veterinary section looked on six topics which are new in the equine veterinary world :

Pasture myopathy – how do latest findings affect UK-based horses?

Pasture myopathy is a disease in horses, more common in Europe in the Autumn, and Helicopter Seed Podcan kill horses who are living out. Affected horses have such severe muscle cramps and breakdown that they collapse, often leading to death. Last year, Horse and Hound reported that risk factors for severe acute myopathy included grazing fields overhung by trees and with accumulations of fallen autumn leaves.

Scientists in the US have discovered that seasonal pasture myopathy is similar to a human disease cause by poisoning with an amino acid called hypoglycin, which is found in unripe Jamaican ackee fruit. When they looked for traces of the toxic metabolites of hypoglycin in the blood and urine of seven affected horses, the scientists found them in all seven. They then searched the pastures where the horses had been grazing for plants, leaves or seeds that had significant hypoglycin levels. They found that some American box elder trees (Acer negundo) produced seeds stuffed with hypoglycin.

This tree was present wherever their clinical cases had gone down with the disease. What was interesting was that the hypoglycin levels in boy elder seeds varied greatly. Seeds from some pastures had 50 times more of the poison than identical looking seeds from the same plant elsewhere. This tree is a member of the sycamore family and produces the typical helicopter like seeds that spin as they fall to the ground.

Box elders are not widespread in Europe, although they have been introduced here, Ornamental varieties with yellow leaves are planted as specimen trees in parks and gardens, where they are more commonly known in the UK as the ash-leafed maple. The English sycamore is, however, very common. Hypoglycin occurs in sycamore seeds too.

Separate Species

donkeyHorses and donkeys are different species of equid. Horses were domesticated from an Asian horse sometimes called the Tarpan, whereas donkeys were domesticated from the African wild ass. Despite the fact that these two species are so different, there is a tendency to think of donkeys as ‘almost or horse’ or to treat them as ‘odd looking’ ponies. This fallacy has been highlighted recently by the publication of reference values for thyroid hormones in the two species.

Spanish vets studied 38 healthy Andalusian donkeys and 19 healthy Andalusian horses kept exactly under the same conditions and fed the same diets. They took blood samples from them at the same time and measured their thyroid hormone levels. The normal, resting and fasting thyroid levels in the donkeys were significantly higher than the corresponding levels in the horses. This means that if the well-publicised horse levels of thyroid activity were applied to donkeys, misdiagnosis could easily occur. A normal healthy donkey would appear to have an overactive thyroid and be misdiagnosed as a hyperthyroid case. A sick donkey with an under-active thyroid suffering clinical hypothyroidism could similarly be blood sampled and declared normal,

The results indicate that the vets must treat donkeys as a separate species with unique metabolic and physiological profiles – a message the Donkey Sanctuary has been preaching for years.

Going Viral

We’re so familiar with flu and tetanus jabs that it seems unthinkable to live in a country where they are unnecessary because the virus does not occur.

Equine influenza is endemic in Europe and much of the US. It occurs at a continual low horse injectionlevel and bubbles up here and there in pockets of infection. The normal flu vaccination programme consists of two primary injections, which the manufacturers recommends should be four to six weeks apart, followed by a third after about five months. Full protective immunity is not achieved until after the second of the two primary jabs. The minimum time between the first two injections under FEI rules is 21 days.

What can the authorities do when an epidemic of the proportion seen in South African in 2003-4 and Australia in 2007 is ripping through the equine population?

In both outbreaks, horses were administered a rapid course of vaccines, the first two given just 14 days apart and the third at about 105 days. Many double this would give sufficient immunity, but it was worth the risk. After a full investigation of this technique, Australian scientists recently revealed that the accelerated course gave the equivalent long-term protection to the recommended course.

This does not mean that we can shorten the interval between our vaccines – this particular one was the most up-to-date product available and not all vaccines would work so quickly. So for the moment, we must stick to FEI and racing rules, but these may change as a result of this research.

Collected vs extended trot – which is worse?

extended trotThe received wisdom about building up young dressage horses has collects suggested that the collected trot is hard on the joints, especially the hocks. But recent research from Newmarket scientists has shown surprising results.

In contrast to what was predicted, it was found that the extended trot placed more strain on the hocks than the collected gait. IN extension, the fetlocks were overextended and therefore dropped more. These are the two factors that are known to contribute to upper suspensory ligament strain – an injury far more common in dressage horses than in other sport horses.

Surface and stress fractures – a link?

horse racingVets have long suspected that the incidence of certain injuries in racing varied according to the type of surface on the track. Horses racing on American dirt tracks appeared to suffer a different spectrum on injuries from those on England’s turf courses. But such hunches have been difficult to measure objectively because there are so many other possible factors.

Vets in California have had the perfect opportunity to test their theories on three courses that switched from dirt to synthetic surfaces in 2006-7. The study concentrated on one specific injury, the stress injury and fracture of the humerus (the chunky bone between the shoulder and the elbow). Vets studied the cases of 841 racehorses who had sustained such injuries in the two years before and after the track surface switchover. With bone-scans, radio graphs and post-mortem findings on record, they could see if surface changes had altered the nature of stress on the bone.

They already knew that the bone could be stressed and fracture either near the top beside the shoulder, or near the bottom beside the elbow. Stress changes near the top were more likely to give rise to catastrophic fractures and the loss of the horse. Those near the bottom commonly caused lameness that resolved with rest.

The study results revealed a clear trend. Horses that raced on dirt tracks were far more prone to stress problems near the top of the bone and therefore to disastrous fractures. Horses that raced on synthetic tracks suffered a higher incidence of injury at the bottom of the bone, but fewer life-ending fractures. The softer and more forgiving synthetic surfaces do cause stress effects on the humerus of young racing thoroughbreds. Stresses are less severe and with less drastic effects, however, than when dirt tracks were used.

Together for donkey’s years

More interesting research on donkeys. It seems they may form close and long-term donkey pairbonds with other donkeys, irrespective of age, sex or biological relationship. This has been observed anecdotally for years, but recently published research now proves it.

Scientists in Edinburgh studied a group of 55 donkeys consisting of 38 geldings and 15 females. By observing them in their social groups and herds, they worked out that 44 of these donkeys had special close friends. This friendship was usually reciprocal – in other words, there were about 22 pairs of closely bonded friends.

They then took 12 of the companion pairs and separated them. One donkey was put in a pen at the end of a menage, next to a pen containing a random donkey. The other member of the best friend pair was able to enter the menage at the far end, where it could see, hear and eventually smell both penned animals.

The scientists observed that the loose donkeys could – and did – recognise their special friends and sought out their company. Regardless of whether the other donkey was a complete stranger or another donkey from their small social group, the behaviour clearly showed that the donkey pals were bonded and wanted to be together.

Such pair bonding is unusual in domestic animals. The research suggests that donkey keepers should take care when groups are split to make sure that best friends are not separated.

 

I found it particularly interesting looking and writing up these articles this week.I previously knew about none of these topics, other than having my own hunches about surfaces in any sport, not just racing. More next week!

Breeding – What can actually be inherited?

This week, Horse and Hound published an article in the verterinary section called ‘Sound in body and mind?’. It was all about what characteristics could actually be inherited from breeding. Such as, can you really inherit personality traits, temprement and even movement style?

Sire Vs Dam

In horse breeding, ‘sire’ is the name given to the father, and ‘dam’, to the mother. But mare and foalwhich parent is more important when it comes to breeding better behaved horses? It’s still a matter of debate, but science is currently looking for an answer. While both sire and da, contribute equally to the genetic make up of the foal, ( half number of chromosomes from the sire, half from the dam) mares contribute during pregnancy and the suckling period in a way that stallions don’t. Nutrition of the developing foetus, as well as exposure to stresses during gestation, can substantially impact the physical and psychological make-up of a foal. Furthermore, the relationship of the newborn with the dam and her behaviour has a major influence on the foal’s temperament. For this reason, although the genetic contribution is the dam, some progeny tests that include a score for temperament attach a value for the dam’s temperament which is twice that of the stallion.

Crucial first three weeks of life: Our interaction with the mare and foal is also critical. Research has shown that gentle handling of the mare has a positive impact on the reactions of her foal to humans. It strongly influences how the relationship with us develops throughout a foal’s life. This effect is noticeable even when the foal is a few days old and can be a deciding factor in the behaviour of older foals. Foals appear to be very tolerant towards humans and novel objects up until around three weeks of age, after which they become increasingly wary. This is very important, as if a young foal has a good early experience, his temperament will be shaped in a positive way that persists later in life.

Temperament Explained

Temperament is a fundamental psychological attribute, often used to describe a person’s or animal’s nature. It is thought that temperament is shaped by indiviual genetic make-up and early life experiences. Temperament also becomes fixed with age, to the extent that most horses and humans have developed a ‘default setting’ upon reaching adulthood.

Behaviour is influenced and shaped by temperament, When looking to purchase horse rearinghorses, owners often talk a lot about the horse’s temperament. A nice temperament would mean a non-aggressive, playful and docile horse, whereas one with a nasty temperament, would be the complete opposite. As well as affecting train ability and performance, temperament is critical to the relationship between horse and rider and can influence risk of injury and accidents. However, through my experiences of owning sports horses, you will often find that their temperament in the stable (ground work) will vastly differ from their temperament during ridden work- usually for the worst.

Two other psychological factors are influenced by temperament- mood and emotional reactions. These are temporary and relatively short-lived responses to current or recent situations. Although these factors are less well understood in horses than temperament, interplay between the three is likely to have a notable impact upon performance.

In 2008, a Dutch study looking into co-operation between horses and their riders found that emotionally reactive horses – those scoring more highly on tests of flightiness and reaction to environmental stimuli, including a tape-recording of a chainsaw – showed more evasive behaviour when being ridden. This showed itself as head shaking, tail switching and shying, which impacted negatively on how they performed.

Evidence that temperament may have a genetic basis comes from our understanding pf evolution. It is through this process that distinct types of horse – differentiated by characteristics such as size, strength and speed – have emerged. Our ancestors may also have selected horses for specific behaviours, creating breeds with defined personality traits that we can recognise today. Our ancestors may also have selected horses for specific behaviours, creating breeds with defined personality traits that we can recognise today.

Support for the idea of evolution of a temperament comes from a 2008 study carried out at Bishop Burton and Moulton Colleges and Harper Adams University. By scoring 1223 horses for six distinct personality traits, researchers identified that certain breeds did appear to have specific temperaments.Thoroughbreds displayed high degrees of dominance, anxiety, excitability, sociability and inquisitiveness. Irish draught horses were more protective, only moderately anxious and less dominant and excitable. Researchers also found that breeds with linked ancestry had similar personalities, consistent with the belief that temperament is an inherited characteristic.

A complex trait

Research has also focused on quantifying the genetic basis of temperament examining its inheritance in groups of Andalusians, Haflingers, warmbloods and thoroughbreds. Estimates of heritability suggest genetics contribute as little as 2% and as much as 30% of a horse’s temperament.

Wide variation in these estimates is due to difficulties in measuring temperament, which is ultimately a matter of opinion, as well as differences in the assessment techniques used. Temperament is a complex trait and its heritability will also vary between groups of horses, depending upon their breeding and upbringing. While these estimates may seem low they are comparable with other measures of performance. Heritability estimates for racing times, for example, in standard bred trotters, Arabs and thoroughbreds vary between 28-40%.

A 2012 study of British Eventing data by the University of Edinburgh revealed that horse showjumpingheritability of performance in sport horses is around 7-9% for dressage, 9-16% for showjumping and as low as 1% for cross country. On this basis, it would appear that temperament is inherited to a similar extent to that of athletic performance. It should therefore play a part in the selection of horses for breeding and the performance-testing of breeding stock and youngsters. This is already the case in some countries, such as Sweden, where stallion performance tests include a temperament one.

Personality tests

How precise are personality tests? In the hope of developing a more accurate way of selecting breeding and young stock, work has been carried out to identify genes that shape temperament. Between 2005 and 2007, Japanese scientists looked at 10 genes that could play roles in determining personality. They studied their association with temperament within a group of thoroughbreds.

Only one gene – which is associated with the chemical dopamine – yielded a positive result, a variation of which was associated with greater curiosity and lower levels of vigilance, or alertness, during the tests. Interestingly, variations of this gene are also associated with novelty seeking behaviour in humans – a personality trait whereby individuals embrace and explore new situations or stimuli.

It could be that horses with that particular copy of gene are more suited to equestrian activities such as cross-country or dressage, where they’re required to confront and deal with challenges. We can undoubtedly breed horses with better temperaments. Given the influence and inheritance of temperament, however, there is clearly a place for the development of more accurate and repeatable personality tests. While science has shown that temperament is inherited and has a genetic basis, it has also highlighted the contribution of non-genetic factors.

We must remember that environmental factors – specifically, the way in which we keep and interact with horses – play a big part in shaping equine personalities.

Apologies for not publishing this article sooner, I could not gain access to my blog on Thursday evening and was too busy yesterday. New article next week!

 

Winter Depression?

This week in Horse and Hound, the vet article looked at if winter really does cause depression in horses. Short days and a lack of sun can cause mood swings and low energy in humans, but is it possible horses can suffer in the same way?

Seasonal affective disorder (SAD) affects 8-10% of people living in northern regions. It is a recognised medical condition that brings about depressive symptoms and lack of energy in winter. Some horse owners believe that their horses are more lethargic in the winter months and less enthusiastic during ridden work. However, this statement is contrary to every experience i’ve ever had with horses in winter. Usually, the cold of winter and their clip brings them into a ‘mental’ phase, meaning that the calmest of horses will turn into a spooky extremely forward going horse.

It is most likely that when owners make these claims, the horse is suffering from something else rather than ‘SAD’. This can include pain from low-grade arthritis in the joints, exacerbated by the colder weather, or from other conditions such as stomach ulcers irritated by an increased amount of hay in their winter diet. Other elderly horses may be suffering from Cushing’s disease, which can cause lethargy in winter. However, in horses were these and others options have been ruled out, could they be suffering from winter depression?

Rhythms of life

Light is the most important environmental factor that controls the body’s rhythms. Its effects on animals that breed seasonally, like horses, is obvious. Along with the photoreceptor cells responsible for vision, the equine eye contains light-sensitive cells that transmit information via the optic nerve to the suprachiamatic nuclei within the brain. These nuclei lie within the hypothalamys and are more commonly referred to as the home of the ‘circadian clock’. It is the structure that oversees body rhythms, partly by determining the release of melatonin-a hormone that controls sleep patterns. In humans we can relate this to our own ‘body clock’. E.g, if we set an alarm for the same time each morning, your body will become accustomed to that time and you will find yourself waking up a couple of minutes before your alarm.

The variations in physiology and behaviour shown by horses and humans throughout any 24 hour period are known as circadian rhythms. While humans are ‘diurnal’ creatures-most active during daylight hours- horses are ‘crepuscular’ meaning they are more active at dawn and dusk. Relating this to my own horse, she is much more enthusiastic to go out for a training session at around 9am or 4pm, rather than in the middle of the day.

SAD in humans is clearly linked to disruption of these circadian rhythms, as winter approaches and the nights draw in. Rather than being able to follow their usual circadian rhythms, as they would in the wild, our horses are generally subject to human driven routine that may well be disrupted further by seasonal variation. Furthermore, prolonged periods of dark lead to increased levels of sleep-inducing melatonin. In humans, this triggers a reduction in serotonin- a lack which can cause depression. We don’t know for sure that the exact same process occurs in horses, it would seem logical to suggest that it might ad=nd this biochemical imbalance could induce similar SAD-like symptoms.

Blind trails

Light therapy, where artificial light is used to counteract darkness during winter months, has proved useful in helping SAD in humans. Little is known about the use of light therapy on the well-being and behaviour of horses, a study being led on on stabled horses by Dr Carol Hall at Nottingham Trent University; it produced interesting results. Horses in the trail were placed under broad-spectrum, high-intensity light, chosen to mimic daylight, for an hour every day for six weeks. Their behaviour before and after the trials was then compared with similar horses who had not received this light therapy. Blind trials were carried out so that the assessors recording the behaviour of the horses did not know which of them had been treated. The criteria recorded were feeding, behaviour, sleep patterns and the horses’ attitude to being handled and ridden.

Although this was only a small study, differences were noted between those horses exposed to the light and those who weren’t. Those who received light treatment showed no significant variation before or after light exposure in any of the areas measured in study. However, the untreated horses were found to be sleeping for longer and were described as lazier at ridden exercise at the end of the six weeks. The yard manager reported that the light-treated group were less grumpy.

Let there be light

The results suggested that keeping horses stabled for long periods-and thus exposing them to longer periods of low light or darkness- may well have the effect of producing SAD-like symptoms at any time of year. Studies in the USA have shown that if a stabled horse is taught how to turn the stable light on, he will; therefore showing that horses prefer the light.

There is an important factor to consider before using light therapy.  The equine eye is adapted for low light levels and their vision is not as good as our in brightly lit conditions. As a prey animal, a horse’s eyes see best at dawn and dusk when its natural predators are most active. While this does not mean the horse needs less light we do in terms of hours per day, it does mean that strong lighting has the potential to cause discomfort. Dr Hall’s study, in addition with our own knowledge of how light affects the horse in other ways, would lend support to the idea that horses should receive light for a generous part of each day. Keeping them in darker environments for prolonged periods may not only represent poor husbandry in terms of quality of life and socialisation with others, bu could-in some ways- lead to SAD.

If depression is suspected and your vet has ruled out obvious physical ailments, exposure to more light may be a good place to start. While much work remains to be done, early studies and anecdotal evidence suggest that light therapy may be a useful tool for gaining optimum equine performance, year round.

 

Apologies for not publishing this article on Thursday evening as usual. I was not able to get the magazine on Thursday or Friday this week. More to come next Thursday!