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!