Healthy horses needed for research study in Saskatchewan

Researchers at the Western College of  Veterinary Medicine (WCVM) in Saskatoon are looking to enrol between 40 and 50 healthy horses for a respiratory study this summer.

The study, led by Dr Julia Montgomery and Dr Katharina Lohmann, aims to determine reliable reference ranges for two common tests used to investigate respiratory disease in horses.

In the WCVM newsletter, Christina Weese writes that that questions about the two tests initially arose when a graduate student was studying lung inflammation markers in normal horses.

“We started looking at what the expected ranges for two common tests – tracheal wash and bronchoalveolar lavage (BAL) – were supposed to be,” explains Dr. Montgomery, an assistant professor in the WCVM’s Department of Large Animal Clinical Sciences.

“In the course of the study, we came across several horses that looked clinically healthy, but their tracheal wash and BAL levels were - according to the current definition - not normal.”

To be eligible for the study, horses should have no history of chronic airway disease, no history of respiratory disease within the last six months and no clinical symptoms at the time of the study. Also, to ensure collected samples remain viable, horses must be within two to three hours’ drive from the WCVM.

An initial examination will identify whether the animal is suitable for the study. The clinicians will perform a clinical examination, including listening to the heart and lungs and checking the temperature. They will also carry out a rebreathing test. This involves placing a bag over the horse's nose, making him breathe deeply, which may make any abnormalities in the lungs easier to detect.

If any signs of abnormality are discovered, the horse will not be suitable for the study and no further tests will be carried out.

If the respiratory system appears normal then further tests to sample fluids from the trachea (“tracheal wash”) and lungs (“brocho-alveolar lavage”) will be performed under sedation.

After samples are collected, team members will examine the blood work for any evidence of inflammation. Dr. Hilary Burgess, a veterinary clinical pathologist at the WCVM, is collaborating with Montgomery and Lohmann to do a cytological analysis of the tracheal wash and BAL samples. The samples will also be sent to the bacteriology lab at Prairie Diagnostic Services (Saskatchewan’s provincial veterinary laboratory) to determine what types of bacteria may be present.

Lohmann and Montgomery say their results will provide invaluable baseline information for equine populations around the Saskatoon area. The study will also help them to identify the next steps for future investigations of equine airway diseases such as RAO.

All study procedures can be carried out at the owners premises, and are free of charge.

The study runs from May to August 2013. More details can be found at:
http://www.usask.ca/wcvm/vmc_clients/respiratory_study/

Measuring response to flexion tests

For many years, opinions on the value of flexion tests in assessing equine lameness have been divided. Now, new research has shown that a system based on a wireless, inertial sensor can be used to measure the horse’s response to a flexion test.

Horses were fitted with sensors on the head, pelvis and right forelimb. The sensors measured vertical pelvic movement asymmetry for both right and left hind limb strides and the average difference in maximum and minimum pelvic height between right and left hind limb strides.

The response to a hind limb flexion test was assessed by an experienced observer and compared with measurements taken with the horse trotting before and after flexion.

John Marshall, lecturer in equine surgery at the University of Glasgow, who led the study, concluded: “A positive response to flexion resulted in significant changes to objective measurements of pelvic symmetry, supporting the use of inertial sensor systems to objectively assess response to flexion tests.

Read more at equinescienceupdate.com

Tapeworms in working donkeys in Ethiopia

Tapeworms are a potential problem amongst working donkeys in Ethiopia research has revealed.

The work, carried out by Dr Mulugeta Getachew formed part of his PhD studies and was funded by the Donkey Sanctuary.

He conducted a serological survey of donkeys from four different geographical regions of Ethiopia. Blood samples were collected from 797 donkeys, that had been naturally exposed to tapeworm infection. None had never been treated for tapeworms.

The tapeworm ELISA test, developed for use in horses, was used to detect parasite-specific serum antibody, IgG(T), in the serum of donkeys. A pilot study had confirmed that the test was suitable for use with donkey sera.

Dr Getachew found substantial serological evidence that donkeys were potentially infected with the tapeworm Anoplocehala perfoliata.

Overall, most animals harboured few parasites and a few donkeys were infected with

large number of parasites. The results indicated that 26% and 8% of the donkeys were moderately and highly infected, respectively. The remainder had low infection intensity or were negative for A. perfoliata infection.

He found a marked difference between results from different regions of the country. Bereh, a mountainous region, had significantly more moderately (51.2%) or highly (23.5%) infected donkeys, than the other midland or lowland regions.

He explains that, in contrast to the other regions studied, Bereh is characterized by pastures that are low-lying and wet, with wide areas of permanent pasture specifically kept for animals and for haymaking.This is likely to result in favourable environmental conditions for the survival and development of both the oribatid mites that are the tapeworm's intermediate host and the tapeworm eggs.

He concludes: “The finding of high sero-prevalence of cestode (tapeworm) infection, which is consistent with the results of coprological and post-mortem findings clearly indicates that cestodosis is one of the major parasitic problems in the donkey population of Ethiopia.”

“These results indicate a risk of intestinal disorders, particularly, colic, associated with A. perfoliata infection in donkeys.”

Read more at www.equinescienceupdate.com

Effect of composting on Parascaris equorum eggs

The eggs of the large roundworm of horses, Parascaris equorum, are particularly resistant to extremes of climate and may survive for many years in stables and on pasture. Composting is becoming a popular method of dealing with waste from equine premises. How likely are P. equorum eggs to survive in composted manure?

A study carried out by researchers from the University of Kentucky Department of Animal and Food Sciences on a central Kentucky horse farm investigated the viability of P. equorum eggs in manure subjected to windrow composting.

For the purposes of this study, a single windrow approximately 42.3m in length, 2.7m in width, and 0.9m in height was built. It contained equine manure, soiled bedding and other waste material, which came from stables occupied by adult stallions and mares. Temperature and carbon dioxide levels within the row were monitored daily. The compost would be mechanically turned and aerated as necessary to maintain optimum conditions. Previous experience had shown that it took 10-12 weeks for the windrow to decompose completely.

Sentinel chambers were used to expose 3g samples of feces to the composting process. The faeces, collected from a weanling foal, had an average of 2216 P. equorum eggs per gram.

The chambers were made of mesh that kept the P. equorum eggs inside, whilst allowing liquids and bacteria to pass through.

 

Chambers were exposed to one of three treatments.

1. Constant exposure. These were placed within the centre of the windrow. Each day after the windrow had been turned, the chamber was placed back in the centre of the windrow.
2. Intermittent exposure. The chambers were placed in the centre of the windrow. On alternate days, after the windrow had been turned, the chamber was placed back in the centre, or placed on the outside of the windrow.
3. Control chambers were kept at 4°C.

Every two days, one chamber from each group was removed and incubated at room temperature for 21 days, at which stage the eggs were examined microscopically to assess if they were viable. (Viable eggs contained larvae.)

Chambers treated with constant exposure contained about 10% viable eggs on day 2 and 0% by day 8. Intermittent treatment resulted in 16% viable eggs on day 2 and 0% by day 6. In contrast , control chambers had average P. equorum egg viabilities of 79% throughout the 18 days of the study.

The researchers concluded that not only was the windrow composting system effective in eliminating viable P. equorum eggs, it did so rapidly. 

 For more details see: http://www.equinescienceupdate.com/articles/ecpee.html

Information sought on saddle slip

Can you spare a few minutes to complete a questionnaire to help research into saddle slip? Scientists at the Animal Health Trust are trying to understand more about the reasons for a saddle to slip persistently to one side in some horses.

To this end they have devised a questionnaire to examine the interactions between horses, saddles and riders.

Saddle slip is a problem seen in all sorts of horses and ponies and can contribute to back pain. It may also be a sign of hindlimb lameness.

A recent study by Line Greve and Sue Dyson at the Animal Health Trust Centre for Equine Studies in Newmarket, found that that saddle slip is not necessarily due to an ill-fitting saddle or asymmetric shape of the horse’s back.

Sue Dyson said: “Detection of saddle slip provides an opportunity for the owner, riders and trainers to detect low-grade and subclinical lameness, with important welfare consequences.”

Greve and Dyson are continuing their investigations, trying to understand more about the reasons for a saddle to slip persistently to one side in some horses. To this end they have devised a questionnaire to examine the interactions between horses, saddles and riders.

The questionnaire should only take a few minutes to complete, and will help reveal the frequency of occurrence of saddle slip and the risk factors involved.  Follow the link for more details...

http://www.aht.org.uk/cms-display/premise_questionnaire.html

Maggot wound therapy

Maggots might be the last thing you'd want to find in a horse's wound. But a recent study assessed the efficacy of maggot debridement therapy in a range of equine lesions and found it was beneficial in 93% of cases.

Over a four year period, Dr Olivier Lepage and colleagues treated forty-one cases (35 horses, 4 donkeys, 2 ponies ) in France and Mali.

The maggots used were sterile common green bottle fly maggots, which have been used in human medicine to clean long-standing, infected or necrotic wounds. Maggots digest fibrin and necrotic tissue, along with bacteria, and secrete proteolytic enzymes and antimicrobial agents into the wound.

Interestingly these are the same species of fly larvae that are the most common cause of fly strike in rabbits and sheep. In horses (and humans) it appears that healthy tissue is able to inactivate the proteolytic enzymes so that only diseased tissue is digested. In contrast, sheep and rabbits can not inactivate the enzymes.

Maggots were applied either directly onto the wound or retained within a polyester net containing small pieces of foam. They were kept in place with cohesive, but not occlusive, bandage – maggots need oxygen.

Between 300 and 900 maggots were used for each wound, depending on its size. They were left in place for three days. In 5 cases the response to the initial MDT was inadequate and so a second treatment was applied for a further 3-4 days.

Conditions treated included limb lacerations, deep seated foot infections and soft tissue abscesses and abdominal incision breakdown. Within just one week a favourable outcome was recorded in 38 of 41 cases. Wounds that did not respond well were those involving neoplasia or a bone sequestrum.

No more than 2 MDTs were needed in this series of cases, in contrast to other reports. The clinicians suggest that this was likely due to the light surgical debridement that was carried out in most cases in this series, before the maggots were applied.

Lepage and colleagues conclude that maggots can be recommended in horses, ponies and donkeys for debridement of wounds and for their potent antibacterial effects – including their use against difficult to control infections such as MRSA and other multibacterial resistant bacteria.

They advise against its use in cases where neoplasia is present. In this study, melanoma and squamous cell carcinoma continued to deteriorate after MDT.

 Read more: www.equinescienceupdate.com

Developmental joint disease in Norwegian Standardbreds

A research project carried out at the Norwegian School of Veterinary Science has revealed that 50.7% of Norwegian Standardbred yearlings suffer from loose bone fragments and lesions in their joints.

Developmental orthopaedic disease is well recognised in the horse, and can result in lameness or poor performance. It can appear in various forms such as: osteochondrosis (OC)/osteochondrosis dissecans (OCD), palmar/plantar osteochondral fragments (POF or “Birkeland fractures”), ununited palmar/plantar eminences (UPE) and dorsoproximal first phalanx fragments.

The aim of the study, led by Sigrid Lykkjen, was to assess the prevalence, development and interrelation of the various forms of developmental orthopaedic disease (DOD) affecting the tarsocrural, metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in Standardbred trotters.

The work formed the basis of her PhD thesis entitled “Genetic studies of developmental orthopaedic joint diseases in the Standardbred trotter”. The research was carried out as a collaborative project between the Horse Clinic and Department of Disease Genetics at The Norwegian School of Veterinary Science, the University of Ås and the University of Minnesota.

Tarsocrural and MCP/MTP joints of 464 Norwegian Standardbred yearlings, born in 2006 and 2007,were examined radiographically. Lykkjen assessed the prevalence of osteochondral lesions and also looked at the interrelation between affected sites.

She found osteochondral lesions in 50.7% of the horses. OC/OCD of the tarsocrural (hock) joint occurred in 19.3%. Of the lesions in the hock joint, OCD of the distal intermediate ridge of the tibia (DIT) was the most common. The prevalence of OC/OCD in MCP joints was 3.6%, whereas the prevalence of POF and UPE in MCP/MTP joints was 23.1% and 3.9%, respectively. 

 

It was common for horses to have similar lesions on the opposite leg. There was an association between OCD of the distal intermediate ridge and OCD of the lateral trochlea ridge, and between POF and UPE.

The high prevalence results for tarsocrural OC/OCD emphasise the need for breeders to take account of these diseases in planning their breeding programme.

^{Read more at: www.equinescienceupdate.com/articles/djdns.html}

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