Good and bad news for donkey lice

Lice can be a problem for donkeys, especially in older or debilitated animals.

Lice are obligate parasites, passing their whole life cycle on the host. This makes them easier to control, but only if they are susceptible to the anti-parasitic products used to control them. Unfortunately, recent work suggests that donkey lice may be developing resistance to commonly used treatments.

Lauren Ellse, Faith Burden and Richard Wall studied the value of pyrethroid-based insecticides on a population of donkey lice. They found a high level of pyrethroid tolerance in the lice tested, and suggested that this was likely to reflect the development of resistance.

In laboratory tests, they assessed the effect of cypermethrin and permethrin on chewing lice (Bovicola (Werneckiella) ocellatus ) collected from donkeys.

They compared the efficacy with that of diazinon, an organophosphate compound to which the lice were unlikely to have been exposed previously.

Neither permethrin, nor cypermethrin, (at concentrations recommended for use on animals) had any significant effect on mortality of B. ocellatus. Combining cypermethrin and permethrin with piperonyl butoxide (which may enhance their activity) did not make them any more

effective.

In contrast, 0.04% diazinon caused 70% mortality within 4 hours and 100% mortality after 24 hours exposure.

Another study raised the possibility of using essential and non-essential oils in the control of biting lice.

Rose Talbert and Richard Wall examined the toxicity of six essential plant oils to the chewing louse, B ocellatus collected from donkeys,

They found that tea-tree, lavender, peppermint, eucalyptus and clove bud showed high levels of toxicity to lice.

They suggest that these botanical products may offer environmentally and toxicologically safe, alternative veterinary treatments for the control of ectoparasitic lice. 

^{See: www.equinescienceupdate.com/articles/gabnfl.html}

Inheritance of size

Horse and ponies come in all shapes and sizes. Domestication and intense selection has resulted in wide variation between breeds.

Work in humans has shown that height is controlled by a vast number of genes, each with only modest effect. What about horses?

Researchers at at Cornell University, New York, have been investigating the genetic control of equine size.

Shokouh Makvandi-Nejad and colleagues in the Department of Clinical Sciences, found that in horses, like other domestic mammals, a small number of genes was responsible for controlling size.
They conducted genome-wide association scans (GWAS) on DNA from 48 individuals from 16 breeds of both extremes of size, ranging from the American Miniature and Falabella to Shire, Percheron and Suffolk Punch, as well as 48 Thoroughbreds.

They found that genetic variation at just four points (“loci”) on the chromosomes could explain most of the variation in size between breeds.

The loci, on chromosomes 3,6,9,and 11, together accounted for 83% of the variation in size differences of the breeds in the study.

“Unlike humans, which are naturally reproducing and possess many genetic variants with weak effects on size,” the researchers comment “we show that horses, like other domestic mammals carry just a small number of size loci with alleles of large effect.“

“Furthermore, three of our horse size loci contain the LCORL, HMGA2 and ZFAT genes that have previously been found to control human height.”

They add that “the simplicity of the genetic control of horse size contrasts greatly with the complexity of human size genetics but is similar to results for the domestic dog.”
See: www.equinescienceupdate.com/articles/ioh.html

Box elder seeds implicated in Seasonal Pasture Myopathy

A toxin present in the seeds of the box elder tree has been found to cause Seasonal Pasture Myopathy.

Seasonal Pasture Myopathy (SPM), a highly fatal muscle disease, occurs particularly in the Midwestern United States and eastern Canada.

Horses with SPM suffer from severe, generalised muscle weakness. They are often unable to get to their feet, or only do so with difficulty. If they are still able to walk, they have a stiff gait - especially of the hindquarters. Affected animals have elevated heart rates, and show profuse sweating and muscle twitching.

The underlying disease process has been shown to be an acquired enzyme deficiency (MADD: multiple acyl-CoA dehydrogenases deficiency) in skeletal muscle.

A similar condition, Atypical Myopathy (AM), occurs in Europe.

Recent research, led by Dr Stephanie Valberg, of the University of Minnesota, showed that the seeds of the box elder tree (Acer negundo) contain hypoglycin A, which can cause SPM.

The study involved 12 horses with seasonal pasture myopathy The researchers examined farms on which SPM had occurred, looking for common factors, and compared them with unaffected farms. Seeds from box elder trees were present on all of 11 SPM-affected pastures and 61% of 23 control pastures.

Examination of box elder seeds from the SPM pastures showed they contained hypoglycin A, a branched-chain amino acid. Once ingested, hypoglycin A is metabolised into MCPA (methylenecyclopropylacetic acid) a toxic compound, which is known to cause multiple acyl-CoA dehydrogenase deficiency (MADD).

The researchers explain that the MCPA “would have a major impact on energy generation, particularly when horses are mobilising fat because of a negative energy balance.” They add ”a negative energy balance was probably promoted in SPM horses by offering little supplemental feed while horses were housed on overgrazed pastures, in some cases during inclement weather conditions.”

Writing in the Equine Veterinary Journal, they conclude: “For the first time, SPM has been linked to a toxin in seeds abundant on autumn pastures whose identified metabolite, MCPA, is known to cause acquired MADD, the pathological mechanism behind SPM and AM.”

“Further research is required to determine the lethal dose of hypoglycin A in horses, as well as factors that affect annual seed burden and hypoglycin A content in Acer species in North America and Europe.”

Read more at www.equinescienceupdate.com

Insect compound may help laminitis

Veterinarians at the University of California, Davis, School of Veterinary Medicine have announced plans for a clinical trial of an experimental drug that has shown promise in treating horses with laminitis.

They report that four horses suffering from laminitis have been treated with the investigational anti-inflammatory drug so far. One experienced a complete remission that has lasted for more than a year, and three others have shown some improvement.

A paper on the first case has been accepted for publication by the Journal of Veterinary Anaesthesia and Analgesia. The journal editors authorised the authors to disclose their findings ahead of publication.

“This is an unusual step for us to announce this so far in advance, but because euthanasia is often the only way to alleviate pain in severe laminitis, we felt that it was important to let the veterinarians and horse owners know that this compound has shown potential as a treatment,” said Alonso Guedes, an assistant professor in the School of Veterinary Medicine.

A clinical trial to assess the drug’s safety and establish a tolerable dose for the compound is expected to begin early 2013. Further clinical trials would be needed to establish the drug’s effectiveness as a laminitis treatment.

The experimental compound, known as t-TUCB, belongs to a group of anti-inflammatory compounds called sEH (soluble epoxide hydrolases) inhibitors. It stems from a discovery made more than 40 years ago by UC Davis entomology professor Bruce Hammock while doing basic insect biology research.

In the paper, Guedes reports the case of a 4-year old Thoroughbred mare that was participating in a study into treating tendon injuries using stem cells, having been retired from racing following such an injury.

The mare developed acute laminitis, which deteriorated despite treatment including cold immersion, antibiotics, leg wraps, and nonsteroidal anti-inflammatory drugs. Before resorting to euthanasia, Guedes and the veterinary team decided to try one last treatment, t-TUCB.

The veterinarians administered the experimental compound intravenously early on the eighth day of the mare's laminitis. They report that, after receiving the first dose, the horse remained standing in the stall most of the day, became interested in her surroundings and walked voluntarily. The mare’s demeanor, posture and mobility continued to improve over four days of treatment.

No adverse affects from t-TUCB were observed, and the mare has remained laminitis-free for twelve months.

Hammock said that work aimed at moving t-TUCB and related compounds toward clinical use is advancing in several areas. He and Guedes are working on compounds with potential for targeting pain and arthritis in companion animals.

See the UC Davis video..

Do local anaesthetics affect MRI findings?

 

Don't rush to carry out MRI evaluations after performing intrasynovial anaesthesia of the digital flexor tendon sheath, warn researchers at the University of Guelph, in Canada. Their work shows that local anaesthetic injected into the digital sheath results in changes that are visible on the magnetic resonance image for at least 72 hours.

The very act of injecting local anaesthetic into tissues can produce physical changes that need to be taken in to account when interpreting bone scans and ultrasound images. Until recently, knowledge of how local anaesthetic techniques influenced the appearance of magnetic resonance images was limited.

Researchers, led by Dr Belinda Black, at the University of Guelph 's Ontario Veterinary College conducted a study into whether anaesthesia of structures in the equine foot caused changes that were detectable on subsequent MRI evaluation.

The study involved fifteen healthy adult horses. None of them was lame, neither had they received non-steroidal anti-inflammatory drugs or undergone perineural or intrasynovial anaesthesia in the previous two weeks.

A baseline MRI examination of both front feet of each horse was carried out before performing the local anaesthetic techniques on one forelimb, selected at random. Mepivicaine was injected around the lateral and medial palmar digital nerves; into the podotrochlear (navicular) bursa; the digital flexor tendon sheath and the distal interphalangeal joint.

The MRI examination was repeated 24 and 72 hours after injection and the images compared.

The research team found that in the case of palmar digital nerve blocks, and injections in the podotrochlear bursa and distal interphalangeal joint, the MRI findings were not significantly different from baseline 24 and 72 hours after injection.. So, they suggest that, when these structures appear distended in MR images after diagnostic anaesthesia, it probably is a true reflection of disease and not simply due to the anaesthetic injection.

This information is particularly important, they point out, since distal interphalangeal joint effusion had been reported as the most common finding on MR images of the equine foot.

In contrast, injection of mepivicaine into the digital flexor synovial sheath resulted in distension of the sheath which was still present 24 and 72 hours later.

Dr Black comments that, although a definite time frame for resolution of digital flexor tendon sheath distension was not determined, she recommends waiting more than 3 days between intrasynovial anaesthesia of the digital flexor sheath and MRI assessment.

She concludes: “our study showed that perineural anaesthesia of the palmar digital nerves and intrasynovial anaesthesia of the podotrochlear bursa or distal interphalangeal joint in sound horses did not have any significant effect on the interpretation of subsequent MR images. However, intrasynovial anaesthesia of the digital flexor tendon sheath caused a significant iatrogenic increase in synovial fluid, which was detectable on subsequent MR images for at least 72 hours.”

Read more at www.equinescienceupdate.com

Hendra vaccine released

Australian horse owners will welcome the news of the introduction of a vaccine* to help protect horses against the deadly Hendra virus. The vaccine, which is available only under permit from accredited veterinarians, will also assist in breaking the cycle of transmission that puts humans at risk of contracting this potentially lethal virus.

Hendra virus is a serious zoonotic infectious disease transmitted by flying foxes shedding the virus in their saliva, urine, aborted foetuses and/or reproductive fluids. Horses are thought to contract the virus by ingesting feed or water contaminated with one of these sources of infection.

With a high mortality rate, Hendra virus has claimed the lives of 81 horses, including nine deaths in 2012 alone. There is no known cure, so the vaccine is positioned to become the most effective defence against this virus.

“This vaccine significantly decreases the risk of exposure to Hendra virus for horse owners, handlers and veterinarians. For that reason, the Australian Veterinary Association recommends that all horses be vaccinated against the Hendra virus,” said Dr Ben Gardiner, President, Australian Veterinary Association (AVA).

“The vaccine will also help to protect the health of horses and is a major win for anyone working in the equine industry, including veterinarians.”

Read more at www.equinescienceupdate.com

Equine Grass Sickness Vaccine Study

Researchers at the Animal Health Trust, Newmarket and the Royal (Dick) School of Veterinary Studies, University of Edinburgh are collaborating in a pilot trial of a vaccine to protect against equine grass sickness.

Equine grass sickness (EGS) is a frequently fatal disease of horses; more than 85% of affected animals die.  It has been reported in several northern European countries, but occurs most frequently in Great Britain, having been first recognised in Scotland over 100 years ago.

The cause is still not known for certain, but it seems likely that toxins from Clostridium botulinum type C are involved.

The pilot study, based in eastern Scotland, has enrolled a total of 100 horses and ponies. This small scale trial is in preparation for a full vaccine trial, which will involve at least 1000 horses and ponies, and is likely to commence in 2013-2014 subject to securing sufficient funding.

Although there is still a lot of work to do before launching the full nationwide vaccine trial, this initial pilot study will help to ensure that the trial design will be practical to perform on a larger scale.

Dr Jo Ireland of the Animal Health Trust, who is piloting the vaccine trial, explains: ‘This is very exciting news and we are working flat out to get the study up and running. There is still a lot of work to do before launching the full nationwide vaccine trial, and this initial study will help us to ensure that the trial design will be practical to perform on a larger scale.’

The Equine Grass Sickness Fund is spearheading the campaign to raise funds for the full vaccine trial, which is being run in collaboration with the Animal Health Trust, The (Dick) Vet and Liverpool University’s School of Veterinary Studies.

Kate Thomson, spokesperson for the Fund, said ‘We are over the moon that the vaccine trial is finally here, but fundraising now starts in earnest to ensure that the full trial can go ahead. Grass sickness takes a terrible annual death toll, and we are appealing to every horse owner in the UK to help bring an end to the disease by donating to this cause’.

If you would like to support the equine grass sickness vaccine trial by making a donation to the Equine Grass Sickness Fund, please visit www.grasssickness.org.uk

New study to investigate headshaking in horses

Headshaking syndrome is an intermittent, apparently involuntary, movement of the horse’s head. It may occur at rest or at exercise. The signs may be so severe as to prevent the horse being ridden.
It is not an uncommon problem, and proves very frustrating to treat. It is thought to be due to pain in the sensory nerves supplying the face (trigeminal nerve).

Although some progress has been made towards both diagnosing and treating the condition in horses, the pathology of the disease remains unknown and further research is needed.

Caudal compression of the infraorbital nerve currently offers the best prognosis for a successful outcome compared with other treatments.

The procedure was developed by Veronica Roberts and colleagues at the University of Liverpool's Veterinary School. Now Clinical Fellow in Equine Medicine in the University of Bristol’s School of Veterinary Sciences, Roberts has received a grant from the British Neuropathological Society to investigate possible focal demyelination of the nerve as a cause of headshaking in horses.

Demyelination is the most common cause of trigeminal neuralgia in people, so the research team will look to see if it is involved in the equine condition. They will collaborate with Seth Love, Professor of Neuropathology at the University of Bristol's School of Clinical Sciences, as he has carried out work in this area in people.

To find a more effective treatment and to understand the disease, Dr Roberts is requesting that anyone who is considering euthanizing a horse due to headshaking to contact her for possible inclusion in her study.

Mobile light therapy

A new way to advance the breeding season in mares is being developed following research into the use of light-emitting diodes (LEDs) to inhibit melatonin secretion.

 

Thoroughbred breeders aim to have foals born as soon as possible after the official birthday of January 1^st (in the northern hemisphere.) This gives them a head start in size and maturity when competing against other horses in the same age group, both at sales and subsequently at the race track.

However, breeding early in the year is at odds with the horse's natural breeding season, which occurs some months later.

Artificial light is commonly used to advance the breeding season in mares. When an early foal is desired, breeders will put the mare "under lights" - keeping the barn lights on in the winter, to mimic the lengthening days that initiate the natural breeding season.

The hormone responsible for controlling this seasonal variation in response to change in day length is melatonin. It is secreted by the pineal gland in response to darkness.

Researchers at the University College Dublin's School of Agriculture and Food Science, have been examining the effect of different levels of blue light on melatonin production.

Four healthy 5-year-old TB mares took part in the study, which was conducted around the vernal (spring) equinox, so the mares were accustomed to equal 12 hour periods of light and darkness. For the duration of the study the mares were housed in a light-tight barn with artificial lighting timed to mimic the conditions outside .

The researchers used LEDs (emitting blue light of wavelength 468nm) set in a head mask to investigate the effect of blue light on melatonin secretion in the horse. (Blue light (465–485 nm) has been found to be the most efficient for inhibiting melatonin secretion in humans.)

Blood samples were collected through indwelling catheters at the end of hour-long periods of exposure to dark or to varying intensities of light. The light was directed at either both eyes or just one eye.

All samples, except the first, collected after exposure to “daylight”, occurred during the dark phase of the 24 h cycle.

The results showed that blue light inhibited the production of melatonin. The inhibitory effect occurred regardless of whether the light was administered to one or both eyes.

Melatonin levels were significantly lower after exposure to 10 lux, 50 lux, 100 lux as well as barn light, than they were after an hour of darkness. Melatonin levels after exposure to 3 lux were not significantly different from those recorded in darkness.

Lead researcher Dr Barbara Murphy, concludes that “melatonin inhibition can be achieved by exposing a single eye to low wavelength blue light.” She adds that “this is a novel finding with important implications for management of artificial lighting regimens in horses.”

“The light mask represents a safe cost-effective method of administering timed low-level light to a single eye so that mares can be maintained outdoors in their natural environment, avoiding the costs of indoor maintenance, while effectively advancing the onset of the breeding season to meet industry timelines.”

Read more at equinescienceupdate.com

Study suggests fatter is naughtier

 

Being overweight is not just a problem in human health; recent research suggests that fat horses and ponies are more likely to misbehave than their more slender companions.

A study, Misbehaviour in Pony Club Horses: Incidence and risk factors, published in the Equine Veterinary Journal (EVJ) is the first of its kind to quantify the incidence of misbehaviour in a population of horses.

Conducted by Petra Buckley, Senior Lecturer in Equine Science at Charles Sturt University, New South Wales,the study involved 84 Pony Club horses from seven different Clubs in rural Australia. Over a period of a year owners kept daily records of horse management including nutrition, healthcare and exercise and recorded any misbehaviour.

Misbehaviour was classified as “dangerous” (such as bucking, rearing, biting or kicking) or “unwelcome” (including “pulling like a steam train”, playing up, resenting foot trimming, and being difficult to catch.)

The horses were checked by a vet every month to investigate any relationship between pain, such as lameness and back pain and misbehaviour.

Of the horses studied, 59% misbehaved at least once during the study year, either during handling or when ridden. Whilst the occurrence of misbehaviour during riding was low, at 3% of horses in each month, in more than half of these cases the misbehaviour was dangerous, and posed a serious injury risk to horse and rider.

Risk of misbehaviour was higher in horses that were fat or obese and in those that were ridden infrequently. Horses exercised more than three times each week were less likely to misbehave. The odds of misbehaviour during riding were more than twice as high when horses were fed daily supplements, such as roughage, concentrates and/or grain. Access to “good grass” was also associated with increased risk of misbehaviour, independent of any supplementary feed provided. Horses and ponies that were excessively fat were roughly three times more likely to misbehave.

This suggests a link between nutrition, exercise, body condition scores and misbehaviour, where higher body condition scores reflect dietary intake exceeding requirements, a problem that can be exacerbated by infrequent exercise.

The study includes recommendations to help prevent misbehaviour such as exercising at least three times a week and maintaining an optimal physique by more closely matching pasture and supplementary feeding to horses’ exercise levels and resulting energy requirements.

“Our results highlight the importance of considering horse body condition, nutrition and exercise in any investigation of horse misbehaviour” concludes Petra Buckley.

Read more at equinescienceupdate.com

Saddle slip may indicate lameness

Saddle slip may not be the result of an ill fitting saddle or asymmetrical back muscles. A recent study has shown that it is often a sign of hindlimb lameness.

The study, conducted at the Centre for Equine Studies at the Animal Health Trust in Newmarket , identified a significant link between hind limb lameness and saddle slip, showing consistent saddle slip in some horses with hind limb lameness, even when the lameness was fairly subtle and difficult to detect.

Saddle slip, in which the saddle slips consistently to one side, is a well-recognised problem in sports horses. It can occur for a variety of reasons, including asymmetry in the shape of the horse’s back, riders sitting crookedly and ill-fitting saddles.

Sue Dyson, Head of Clinical Orthopaedics at the Centre for Equine Studies, had also observed that saddle slip may occur because of hind limb lameness. The intention of the study, therefore, was to find out more about the interrelationships between the horse, saddle and rider and to document the frequency of occurrence of saddle slip in horses with hind limb lameness compared with other horses.

The research was undertaken by Line Greve, Intern at the Centre for Equine Studies, and Sue Dyson, and was presented at the British Equine Veterinary Association Congress in September 2012. It is thought to be the first study of its kind, and was supported by the Saddle Research Trust (SRT).

The study assessed 128 horses of varying size, age and type. The degree of lameness of each horse was graded; back shape and symmetry were measured and saddles assessed for symmetry and fit. Each horse was ridden by at least two riders and rider straightness plus weight were recorded. The grade of saddle slip, whether it occurred with more than one rider, and whether saddle slip was influenced by the direction of movement or the diagonal on which the rider was sitting were also noted.

The saddle consistently slipped to one side in 54% of horses with hind limb lameness, compared with 4% of horses with fore limb lameness, 0% with back pain and/or sacroiliac joint region pain and 0% of non-lame horses. The saddle usually slipped towards the side of the lame (or more lame) hindleg.

Diagnostic analgesia was subsequently used to abolish the hind limb lameness and this eliminated the saddle slip in 97% of cases.

Sue Dyson said: “Our findings emphasise the need to educate owners, veterinarians, physiotherapists, trainers, riders and saddle fitters that saddle slip is frequently an indicator of lameness, not necessarily a manifestation of an ill-fitting saddle or asymmetric shape of the horse’s back. Detection of saddle slip provides an opportunity for the owner, riders and trainers to detect low-grade and subclinical lameness, with important welfare consequences.”

Minimising the stress of weaning

What is the least stressful way to wean foals? A small scale pilot study compared three different procedures.

The research was carried out at the Graf Lehndorff Institute for Equine Science, Neustadt (Dosse), Germany, under the direction of Professor Christine Aurich. A full report of the study has been published in the journal Stress.

Different weaning procedures were used for each of three groups of mares and foals. Each group comprised 6 (or 5) mares and foals.

Methods of weaning used were:

• Group A (6 foals): all foals in the group were weaned at the same time

• Group B (5 foals): all foals were weaned at the same time, but were left with two mares with which they were familiar, but not related.

• Group C (6 foals): these foals were weaned by removing two mares from the group on each of three consecutive days

During the weaning process, the researchers monitored the foals' behaviour and movement. They also measured the concentration of cortisol in the foals' saliva, recorded their heart rate and variability, and their weight.

The results confirmed that weaning was associated with stress. All groups showed an increase in salivary cortisol on the day of weaning. In Group C the cortisol concentration remained elvated for two days.

Abrupt weaning with no further contact with adult animals seemed to be the most stressful. Foals in Group A lost weight for two days. They seemed more unsettled - spending more time moving about on the day of weaning. They also showed the most pronounced increase in heart rate.

Foals that were weaned in the presence of two familiar but unrelated mares, (Group B) seemed least affected by the weaning procedure. Of the three groups, they showed the least locomotion and vocalisation after weaning.

The researchers conclude: “Based on cortisol release and behavior, weaning is associated with stress but this was least pronounced in foals weaned in the presence of two familiar but unrelated adult female horses.”

Fixed time protocol for frozen AI

A fixed time insemination protocol described by researchers from Brazil could encourage a greater use of frozen semen in equine reproduction.

One of the reasons frozen semen is not more widely used for breeding mares is the need for insemination to occur close to the time of ovulation. This necessitates repeated ultrasound examinations when the mare is in season, making the technique time consuming and labour intensive.

For artificial insemination with frozen semen to become more widespread, a simplified routine is needed that is less labour intensive, but does not sacrifice fertility.

Bruno Ribeiro Avanzi and colleagues at the Department of Animal Reproduction and Veterinary Radiology, Universidade Estadual Paulista at Botucatu, used a fixed time insemination protocol to achieve conception rates comparable with those using a more traditional approach.

Semen from two stallions was used in the study. One stallion (A), a Westphalen, was of good fertility, the other, (B) a Mangalarga Marchador, was of poor fertility.

The semen was collected, processed and frozen using a standard method.

Twenty nine mares were enrolled in the study. The oestrus cycle was monitored by rectal palpation and ultrasound scanning. Once a pre-ovulatory follicle of at least 35mm diameter was present, each mare received an injection of the gonadotrophin releasing hormone deslorelin acetate.

Growth of the follicle was monitored every six hours, starting eighteen hours after the deslorelin. Half of the mares were inseminated when ovulation had been detected, the others were inseminated 40 hours after the administration of deslorelin regardless of whether ovulation had occurred or not.

All mares were inseminated into the tip of the uterine horn adjacent to the follicle.

For frozen semen from the fertile stallion, the researchers reported pregnancy rates of 46.7% (7/15) when bred 6 hours after ovulation, and 66.6% (10/15) for inseminations performed 40h after ovulation induction.

The less fertile stallion achieved pregnancy rates of 35.7% (5/14) when bred 6 hours after ovulation and 21.4% (3/14) for inseminations performed 40h after induction of ovulation.

The researchers conclude that insemination at a fixed time after ovulation induction is efficient. “The present data supports the feasibility of equine frozen semen as a technology to be widely used and spread since it reduces mare management and costs.”

Read more at equinescienceupdate.com

Single mutation affects horse gaits

Scientists in Sweden have announced an important discovery that helps explain how some horses are limited to “natural” gaits, while others are capable of additional gaits.

Nearly all horses use “natural” gaits (walk, trot, canter and gallop) without special training. Additional “ambling” gaits may occur naturally in some individuals, but usually only in certain breeds.

Researchers have identified a single gene mutation that enables horses to perform gaits such as running walk and pacing. The pace is a lateral two-beat gait; the two legs on the same side of the horse move forward together, unlike the trot, in which the two legs diagonally opposite each other move forward together.

Not only does the mutation play a crucial role in the horse's ability to perform “ambling” gaits, it also affects performance in harness racing.

Leif Andersson and his research team in the Department of Animal Breeding and Genetics, at the Swedish University of Agricultural Science were looking for a genetic basis for gaits in horses. Only some horses can pace, and they wanted to find out why.

 

They studied the genomes of 70 Icelandic horses that could perform extra gaits — 40 could pace, and 30 could perform other alternate gaits. They found that a single mutation in a gene called DMRT3 was strongly associated with the ability to pace. The mutation resulted in the production of a shortened form of the DMRT3 protein. Both copies of the gene were mutated in the pacing horses.

Andersson explained that horses without this mutation cannot move their right hindleg and right foreleg forward at the same time. But with the mutation the movement is not regulated so strictly and becomes more flexible.

“We suspected a strong genetic component, but were almost shocked when we discovered that a single gene, DMRT3, largely explained the genetic difference between pacers and non-pacers’” said Lisa Andersson, one of the PhD students involved in the project.

The researchers developed a diagnostic test and found that the mutation is widespread among horses that show alternate gaits like Tennessee Walking Horse from the USA and Paso Fino from South America.

The mutation must have originated over a thousand years ago, Andersson said, judging by its widespread distribution among breeds. The horses with this gene would have given a smoother ride and thus been kept and bred.

While Andersson's group were investigating the presence of the gene mutation in pacing horses, a second research team was investigating the expression of the DMRT3 gene in the spinal cord of mice.

Klas Kullander and colleagues in the Department of Neuroscience, at Uppsala University, found that the gene was expressed in a previously unknown type of nerve cell within the spinal cord.

Further investigation showed that the DMRT3-neurons cross the midline of the spinal cord, connecting the left with the right side. They also connect with motor neurons that control flexor and extensor muscles. It seems that, as well as coordinating the activity of flexor and extensor muscles, this network of nerve cells also controls the alternate movement of left and right limbs.

‘The discovery of the DMRT3 mutation is an outstanding example of how genetic studies of evolution in domestic animals can lead to basic new knowledge concerning gene function and important biological mechanisms’, said Leif Andersson.

‘It is truly great when this type of interdisciplinary collaboration results in such ground breaking discoveries. There was no information in the scientific literature on the function of the DMRT3 prior to the publication of our article. This protein is present in all vertebrates for which data are available, and it is likely that DMRT3 nerve cells have a central role for coordinating movements in humans as well’, added Klas Kullander.

More details at equinescienceupdate.com

BHA announces new Detection Times

The British Horseracing Authority has announced that it has adopted five new Detection Times for Romifidine, Salbutamol, Firocoxib, Butorphanol and the Romifidine/butorphanol combination.

These Detection Times are harmonised across the member countries of the European Horseracing Scientific Liaison Committee (EHSLC). The EHSLC has been investigating the detection times of commonly-used medications, in response to the need for more information on the time taken for drugs to be eliminated.

In addition, the BHA detection Time for Detomidine/Butorphanol has been harmonised with the Detection Time across Europe and raised from 48 to 72 hours. Most of these new Detection Times result from research performed at the Authority’s Centre for Racehorse Studies in Newmarket.

The “detection time” is the time at which the concentration of the drug (or its breakdown products) in the urine, is not detected using routine or standard methods, in all the horses in the study.

It is important to remember that “detection times” are not the same as “withdrawal times”. An additional safety margin should be added to allow for individual variation.

However, the figures will give some welcome guidance to veterinarians who have to advise on whether a horse is likely to test positive if treated in the days before a race.

Further information, including a downloadable sheet of all 31 BHA Detection Times, together with a full explanation of the limitations of the results, can be found on the Authority’s website

http://www.britishhorseracing.com/resources/equine-science-and-welfare/medication-control.asp

Information on withdrawal of supplements containing Devil’s Claw has also been added to the Notices section of the Authority’s Rules website, where further information the use of a number of medications can also be found.

http://rules.britishhorseracing.com/Orders-and-rules&staticID=126908&depth=2

Possible blood test for inflammatory airway disease?

Inflammatory airway disease (IAD) is a common cause of poor performance in the equine athlete. Affected horses may cough as well as showing exercise intolerance, but a definitive diagnosis is based on examination of bronchoalveolar fluid (BALF.) This involves passing a tube into a sedated horse’s lung. A small amount of fluid is introduced and withdrawn, and the cells that have been washed from the lung are collected and examined microscopically.

Research at a laboratory in France may lead to the development of a simpler test for IAD. Eric Richard and colleagues at the Frank Duncombe Laboratory at Caen have been investigating the value of a blood test for a protein present in the lung for identifying horses with IAD.

Surfactant protein D (SP-D) is produced mainly by specialised cells in the alveoli and bronchioles, but has also been found in joint fluid and in the reproductive tract. It plays a role in immune defences in the lung

SP-D is released into the blood stream in response to tissue damage, and is used routinely in human medicine as a marker for inflammatory lung diseases.

The study, which compared SP-D levels before and after exercise in horses with and without inflammatory airway disease, has been reported in the Equine Veterinary Journal.

The researchers found that IAD was associated with a detectable, though moderate, increase in SP-D levels in the blood.

Within the IAD-affected group, they found no significant correlation between serum SP-D concentrations and BALF cytology. Neither did they find a significant effect of exercise on serum SP-D concentration in either the IAD or control groups.

A non-invasive test for IAD would benefit both horse and owner, being less stressful for the horse and cheaper for the owner. However, the report's authors advise that more work is needed to understand the factors controlling blood levels of SP-D. They advise caution before applying their findings to clinical cases.

More details:  equinescienceupdate.com

Music and stress response in weanlings

Scientists at the University of Queensland have found that music therapy may help reduce the stress associated with weaning.

Twelve weanlings that had been raised together were divided into two groups, matched for temperament. At weekends, all weanlings were turned out together. On week days, one group remained in the paddock, while the other group was stabled, with or without soothing music. Eventually both groups had been stabled for five days with music and five days without.

During the music treatment weeks, the Forest Gump Main Theme by Alan Silvestri was played continuously from 09.00 to 15.00 h daily. This particular piece of music was chosen for its constant rhythm, continuity and predictable melody.

The research team recorded heart rates every day from 09.00 to 15.00 h using heart rate monitors. They also recorded each horse's behaviour.

They found that although music did not affect the median heart rate, it significantly reduced heart rate variability. Furthermore, behavioural measurements showed that weanlings were more relaxed, and spent more time eating rather than walking about the stable, when they were exposed to soothing music.

Twice a week the weanlings were exposed to stallions in nearby stables. This gave the research team the opportunity to assess the effect of music on the weanlings' response to stress.

They found that, when music was being played, the peak heart rate in response to stress was substantially lower and the duration of increased heart rate was shorter.

The researchers conclude that their findings suggest that stress responses in weanlings can be modified by playing music whilst in stables. They suggest that the application of music therapy to enrich the equine environment is an area that shows promise and requires further study.

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Legibility of hot iron brands

The debate about the use of hot iron branding for identifying horses is becoming as heated as the branding iron itself. Critics of the procedure maintain that it causes pain and stress, which is no longer acceptable since the advent of microchip technology.

Others point out that not everyone carries a microchip reader with them. At least brands are easy enough to read without special equipment. Or are they? Recent work suggests that hot iron branding is not as accurate a means of identification as its supporters claim.

Until recently, horses were generally branded but following concerns that the practice is unnecessarily cruel there has been a gradual switch towards the use of microchips. Branding has essentially been discontinued in the European Union, although it is still accepted in several countries. Breed registries claim that this traditional method is perfectly satisfactory and obviates the need for costly equipment. Typically, a brand will comprise a symbol to indicate the particular breed combined with a two-digit number to identify the individual animal.

Comparisons between the two methods for identifying horses have focused on how they are perceived by the animals: does either method cause more stress or more harm to the horse?

Surprisingly, however, no attention has been paid to the other side of the coin. There is no doubt that microchips can be unambiguously decoded, providing the necessary equipment is available, but how well can brand marks be read? The issue has now been examined by Jörg and Christine Aurich of the University of Veterinary Medicine, Vienna.

According to the study, reported in the Veterinary Journal, three breed experts could only accurately identify the brands on less than half of the horses presented to them.

To assess the legibility of the markings, the researchers asked three experienced people to record the brands of 248 horses participating in an equestrian tournament in Germany.

All three experts were able to recognize the breed symbols on about 90% of the animals. For about 84% of the animals the symbol was recorded correctly by all three people.

However, reading the two-digit numbers proved more problematic. While each of the three readers correctly read the numbers on about half of the horses, the correct number was recorded by all three of them for less than 40% of the animals.

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PCR beats serology for leptospira detection

Examining urine using a polymerase chain reaction (PCR ) technique is more reliable than serology for identifying horses infected with leptospirosis, according to scientists in Brazil.

Leptospirosis can cause various clinical signs, including abortion, uveitis, and kidney and liver disease. Sub-clinical infections also occur, in which infected horses show no signs, but carry and excrete the organism.

In a letter to the Veterinary Record, Hamond and others report the findings of a study that assessed the relative merits of serology and urine PCR for detecting Leptospira infection in horses.

Their research looked at four herds in Rio de Janeiro, Brazil. Previous cases of leptospirosis had been recorded in the herds, and none of the horses had been vaccinated against the disease.

Blood and urine samples were collected from all adult horses (144). Leptospira antibodies were found in 66 horses, and 89 horses had Leptospira DNA in the urine.

Over half of the Leptospira-positive urine samples came from horses with no Leptospira antibodies in the blood.

The authors conclude that in horses, “serology is a useful tool for detecting leptospirosis on a herd basis, but individual detection of Leptospira species carriers must rely on PCR.”

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Role of bacteria in chronic laminitis

 

Recent research suggests that bacteria may play a more significant role in chronic laminitis than previously thought.

Its not uncommon for abscesses to form underneath the dorsal hoof wall in horses with chronic laminitis. But whether these are the result of aseptic destruction of the laminae, or the result of bacteria tracking up the horn tubules is a matter of debate.

A study, by Janet Onishi and colleagues, based at Rutgers University, New Jersey, USA, investigated whether horses with chronic laminitis had evidence of sub-clinical infection in the laminar tissue.

“The objective of this study was to establish whether bacteria colonize laminar tissue and whether horses with chronic laminitis have higher or different microbes in the laminar tissue compared to non-laminitic horses” they explained.

Hoof samples were collected in a sterile manner from five horses with chronic laminitis, and from eight horses with normal feet.

The researchers found that laminae from horses with chronic laminitis contained 100 times the number of bacteria than did laminae from unaffected animals.

Only a few bacteria, all Gram-positive organisms, were isolated from the laminae of the healthy horses. In contrast, the laminae from chronic laminitic cases contained many more bacteria. Again Gram-postive organisms predominated, including bacteria in the phylum Actinobacteria, and coagulase negative Staphylococci. Many of the bacteria were identified as potential pathogens.

“The bacteria recovered from laminar tissue of chronically laminitic horses are not only potentially pathogenic, but are also known to form biofilm infections. “

(A biofilm is a complex community of micro-organisms, typically attached to a surface. Bacteria within the biofilm may be less accessible to host defences and antibacterial agents. A common example of a biofilm is dental plaque.)

The researchers suggest that horses may develop chronic laminitis as a result of biofilm infections occurring after an initial episode of acute laminitis. “We propose that treating chronically laminitic horses is difficult because there is a bacterial component to the disease that is not understood.”

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Scientists question training method

Research from the University of Sydney questions whether the round-pen (“Join-up”) training method made famous by Monty Roberts is really as humane as its supporters claim.

Lead researcher was Cath Henshall, an animal science masters degree candidate in the Faculty of Veterinary Science.

She explains: “This method of training is widely used around the world and the people that use it claim that it's a humane and kind way to train horses. They also claim that it works because the trainer is able to successfully mimic horse body language and horse behaviour.

“Our study casts doubt on both those claims. We believe that our research highlights the unpleasant underpinnings of round pen horse training and for that reason we caution against its widespread use because it uses fear to gain control of horses."

The technique relies on the trainer using movement and noise to drive the horse around the perimeter of the pen. The trainer gradually reduces their aggressive movements, after which the horse will eventually slow down and approach them.

The researchers used remote control cars to mimic the technique and to eliminate the role of the trainer in imitating the horse's body language.

They believe that the training outcomes were achieved as a result of 'pressure-release' and not the ability of the trainer, or a remote control car, to mimic horse behaviour. "Put simply,” said Henshall, “pressure-release works because the horse finds the pressure applied unpleasant and therefore the removal of the pressure rewarding.”

The response the horse makes immediately before the pressure is removed is what the horse thinks made the pressure go away. When put in the same situation in the future, it is likely to perform that same behaviour to obtain the outcome that it values – safety.

"We 'rewarded' the horses for stopping and turning towards the car with a period of 'safety', when the car didn't chase them as long as they kept facing it. We trained some horses to actually walk up to and touch the car," said Henshall.

“We found that the car is almost as successful as the human trainer, so we think that calls into question whether the horse is responding to the human as though they think the human is another horse. We also confirmed that the reason the training works is for the same reason all horse training and a lot of animal training works. So that it doesn't actually require that you understand horses' body language particularly well. It just requires that you're able to chase and not chase at the right time.”

"Given that we could train horses to produce similar, though not identical responses to those seen in round pen training, but in reaction to non-human stimuli undermines the claim that the human's ability to mimic horse behaviour is an essential component of the technique."

"Although neither Monty Roberts' method nor ours uses pressure applied directly to the horse's body, both apply a form of emotional pressure by scaring and then chasing the horse."

"Our results indicate that because these methods rely on fear and safety, the horse is forced to choose between being repeatedly frightened or remaining with the trainer. We question whether it is humane to rely on fear and its termination to train horses," said Henshall.

"Although it is appealing to think that horses in the round pen choose to follow their trainers because they are responding to us as though we are a horse, we believe that the use of fear has no place in genuinely humane and ethical horse training."

 

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www.equinescienceupdate.com/articles/sqtm.html

 

 

Ten minutes of Low-Deep-and-Round may cause stress

Compared to other head and neck positions, horses ridden in hyperflexion, or “low deep and round” are likely to be exposed to higher levels of physiological stress, according to work presented recently at the International Equitation Science Conference in Edinburgh.

Previous studies explored the effects of the hyperflexed head and neck position on the stress and behavioural responses of horses on the lunge or a treadmill. This study, by Dutch and Danish researchers measured a variety of behavioural and physiological responses of horses ridden in hyperflexion and two other common head and neck positions.

Fifteen Danish dressage horses training at medium to Grand Prix level and routinely ridden in the hyperflexed head and neck position were used. In addition to hyperflexion, low deep and round, the standard “on the bit” or competition frame and loose frame in which there was less tension in the reins were also investigated. Each rider performed a pre-determined riding test of 10 minutes duration in walk, trot and canter in each of the three head and neck positions, randomised over the three days of testing.

Heart rate, heart rate variability, salivary cortisol concentration, behaviour and the tension in reins were recorded during the 10-minute test period. Salivary cortisol concentrations were measured 60 minutes before and 0; 5; 15 and 30 minutes after the test.

“This study is the first to test whether there is an acute stress response to the hyperflexed head and neck position in horses ridden in a typical training environment” said Dr Machteld van Dierendonck from Utrecht University. “We found that the increases in salivary cortisol concentrations from baseline were significantly higher after 10 minutes of riding in the hyperflexed position than the increases observed in the competition head position or with the loose frame.“

Cortisol is known as the ‘stress’ hormone and increased cortisol concentrations are routinely used to quantify stress responses in animal welfare studies.

“We didn’t find any significant differences in heart rate, and heart rate variability between the treatments, but we did find that certain behaviours were higher during hyperflexed riding than the other head positions. Rein tension during the hyperflexed and competition head position was significantly greater than during the loose frame position.”

“Compared to previous studies which have used side reins to maintain the hyperflexed position, the low, deep and round position in this study was less hyperflexed.” she said.

“We wanted to test the horses’ response to this method in a typical training environment. Within the parameters of this training situation, we found that the use of the hyperflexed head position, even in horses routinely ridden this way could result in a physiological stress response as measured by salivary cortisol concentrations.”

“Interestingly, riders indicated a loss of balance and steering control in the loose frame”.

Head and neck positions has been the subject of controversy with the FEI conducting two reviews in recent years.

This study was a joint work with Danish and Dutch universities. Janne Winter Christensen from Aarhus University in Denmark, along with Mirjam van Dalum, Mandy Beekmans from Utrecht University were joint researchers on this study.

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Effect of weather on equine flu outbreak

Analysis of the recent Australian equine influenza outbreak has improved understanding of how the disease spreads.

Researchers from Australia and New Zealand looked back at the outbreak, which took place between August and December 2007. It was estimated to have cost the Australian equine industry over $350 million. Almost 70,000 horses on more than 9000 premises in Queensland and New South Wales were affected. The country had previously been free of the disease.

Simon Firestone, lead researcher and PhD candidate at the University of Sydney's Faculty of Veterinary Science. and colleagues matched meteorological data with information from infected premises to assess the effect of the weather on the spread of infection.

They discovered an association between the occurrence of new cases and the weather conditions three days previously. This coincides with the incubation period for equine flu – the first signs are usually seen from 3 days after the animal becomes infected.

The researchers found that horses were more likely to get infected on drier days when relative humidity was low. There was minimal risk once relative humidity exceeded 80%.

Infection was also less likely on days when the maximum daily air temperature was between 20 and 25°C. Extreme temperatures, either high ( >28°C) or low (<16°C) were associated with the highest risk of infection. Lower minimum daily temperatures were associated with higher risk of infection.

The researchers also found that wind speeds in excess of 30km/hour from the direction of infected premises were associated with increased risk of infection.

 

In conclusion, the authors write: “by combining influenza outbreak and concurrent meteorological data, we have shown how relative humidity, air temperature and wind velocity combined to influence the spread of an actual influenza outbreak.

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