Nearly every horse owner has trailered a horse from point A to point B. Many horse owners do it on a regular basis, going to competitions, rodeos, or rides every other weekend or so. We make sure the vents in the trailer are adjusted properly to account for the outside weather. We protect our horses' legs, hooves, heads (and sometimes other parts of their bodies) so they don't get banged up. We drive carefully around corners, and avoid potholes and quick stops and starts. We give them a bit of hay to keep them occupied and happy, throw some straw under them to help with clean-up, and check on them when traveling several hours.
KIM AND KARI BAKER PHOTO
If people are traveling every weekend and the horses are exercising during the week, then there probably is a cumulative effect.
Even with all of this TLC, our horses are stressed when they travel.
The motion of the trailer, even over the smoothest road, means exercise for the horse to compensate for the movement under his feet. And he has no warning of what is coming on the road ahead. (Imagine what he has to do when you drive over the ruts and gullies in the field to park at the show, or travel up the twisty gravel road to get to the trailhead. Then after that marathon, he has to get out and compete!) His environment is contaminated and closed and his movement limited while he is in a trailer, even with the most meticulous cleaning and the most open trailer design. Horses urinate and defecate in their stalls, causing a build-up of ammonia and bacterial matter in the air that will be inhaled. Bits of hay, hair, and whatever gets blown in the vents or windows fly about inside the trailer, just waiting to get into your horse's respiratory system.
As if this weren't enough, the mental stress of traveling will take its toll on some horses, making the exertions of the intended competition secondary.
With seasoned campaigners, the rigors of travel itself might seem less traumatic. However, the cumulative effect of travel does have an impact on a horse's respiratory and immune systems. A recipe for lung injury that could lead to anything from the inconclusive "not doing well" to full-blown pleuropneumonia is the following: Train hard at home, load and travel to the show, compete and mix with other horses (possibly picking up a new "bug"), load and travel home, repeat.
So, what's a horse owner to do?
That is the question a group of veterinarians and researchers asked themselves (see The Horse of May 1999, page 8). The same core group who was committed to mitigating the circumstances of the summer heat and humidity of Georgia for the 1996 Olympics convened a workshop of the world's top "equine travel agents," if you will, to look at the issue of transportation.
The workshop of these world leaders soon will produce for horse owners a set of guidelines for equine travel. The guidelines should be available to all horse owners by the end of the summer. They are being published by the American Horse Shows Association in book form. However, the main topic of discussion was, "What don't we know about equine transportation?"
There are very few horses in the world which will never step foot on a trailer during their lifetime, whether to travel to competitions, pleasure rides, sales, or just to another farm. Because of this world-wide impact, transportation is one of the hottest topics in equine health.
Competitions literally are won or lost on the ride to the show.
But, say the researchers and veterinarians, while there has been research on travel, there have been no epidemiologic studies to pinpoint exact areas of concern. "We all know airway inflammation is a problem," they say unanimously. Without statistical backing, however, they don't know if tying the horse's head up really is the number one contributor, or if it is the hay, or the way the horse faces, or the ventilation, or bacterial contamination, or pre-shipping health status, or ?
"Colic and injuries are seen." But how often and under what circumstances?
Researchers say if they know the problems and know the prevalence of those problems then they can develop ways to mitigate or eliminate those problems, much as they did with the heat and humidity studies.
Being able to say, "If we change these conditions, we can benefit the horse" is the goal of the planned research. And the goals are attainable, if enough talent, energy, and funding are available to conduct the studies.
Participants for the roundtable on transportation are as follows:
Kent Allen, DVM, is owner of Virginia Equine, a private imaging and lameness consulting clinic in Middleburg, Va. His clients mostly are athletes who compete in the three Olympic disciplines of dressage, jumping, or three-day eventing (and all of which travel extensively for competitions and training). He also has been a team veterinarian for the U. S. three-day event team and was one of the core people on the heat and humidity research team that conducted studies in the four years preceding the 1996 Olympics in Georgia.
Ray Geor, DVM, is president of the Association of Equine Sports Medicine. Geor has an interest in exercise physiology and how transportation affects athletic horses. He currently is completing a PhD in equine exercise physiology at The Ohio State University.
Professor Leo Jeffcott, MA, BVetMed, PhD, FRCVS, DVSc, is Dean of the Veterinary School at the University of Cambridge and is Professor of Veterinary Clinical Studies. Jeffcott is currently Chairman of the FEI Veterinary Committee, a member of the Bureau of FEI, and he will be President of the Veterinary Commission for the Sydney Olympics in 2000
James H. Jones, DVM, PhD, is a professor of comparative physiology in the Department of Surgical and Radiological Sciences at the School of Veterinary Medicine, University of California, Davis. Jones has worked with Japanese researchers on transportation studies, as well as conducted research on transportation at UC Davis.
Catherine Kohn, VMD, is on staff at The Ohio State University veterinary school. She is an FEI veterinary delegate to many three-day events, including the 1996 Olympics and 1999 Rolex Kentucky Three-Day Event. She was one of the leaders in the pre-Olympic heat and humidity studies, and she is putting together the guidelines from the transportation workshop.
Desmond Leadon, MA, MVB, MSc, FRCVS, RCVS, registered C/specialist in equine medicine, is the head clinician in the Pathology Unit at the Irish Equine Center. He has published numerous scientific articles pertaining to transportation, and is considered the "guru" of air transportation of horses.
Masa-aki Oikawa, DVM, PhD, is the Vice-Director of the Equine Research Institute of the Japan Racing Association (JRA). The JRA probably has conducted more studies on equine transport than any other group because of the way horses are trained at training centers in Japan, then shipped to races, and because the JRA has control over the health and well-being of those horses.
N. Edward Robinson, BVetMed, PhD, MRCVS, Docteur Honoris Causa (Liege), is the Matilda R. Wilson Professor of Large Animal Clinical Sciences at Michigan State University College of Veterinary Medicine. Robinson has authored or co-authored numerous scientific articles, book chapters, and books (including Current Therapy in Equine Medicine 4) on equine veterinary medicine, and his major research focus is in equine respiratory problems.
Why should we think about transporting horses as a problem?
Kohn: The effects of transport on horses are multiple and complicated. During transport, the horse is removed from its home environment and required to tolerate a confined space. The air in the transport vehicle may contain many contaminants such as dust from hay or bedding, ammonia fumes, and exhaust fumes. We are asking the horse to remain calm and quiet in this environment, despite little room to move, and possibly a bumpy ride, punctuated with multiple stops and starts. Maintaining balance through frequent postural adjustments during transport is work for the horse. Sometimes, horses are transported for long distances or a journey of a short distance may take a long time due to road or weather conditions, or problems with the transport vehicle. During transport the horse may not eat well, may drink little, and may become dehydrated. In short, transport is likely to be tiring for horses just as it is for humans. Our goal is to define the effects of transport on horse health, and to find strategies for making travel as pleasant and safe an experience for horses as possible.
Leadon: Let me suggest to you that we mustn't think about it as a problem. It is something that the industry has evolved highly successfully, but like anything else, we probably can do it better. Improvements should follow on better understanding and further research.
Oikawa: Transportation is a problem because transport is considered to induce a number of behavioral, physiological, and pathological responses in horses. Thus, transport has proven to be stressful for horses. In a viewpoint of animal welfare and athletic performance, it is desirable to reduce transit stress in horses.
Jeffcott: There are, of course, many ways that things can go wrong when horses are transported, but it is the respiratory system that seems to be the body system at most risk to stress and damage. Therefore, one of our priorities must be to learn more about the response of the respiratory system to different transport situations.
Allen: Any sort of travel with the horse involves a stress on the horse's part. All horses, unless they are wild mustangs, at some point travel in their lives. It certainly affects all horses that do anything in the pleasure or competition arena.
I have horses come to my clinic that get off the trailer coughing and with mucous congestion and mild respiratory issues that have to be dealt with.
Geor: We know that transport can adversely affect horses, but a great deal more research is required to improve our understanding in several areas. It is only through such research that we will be able to develop strategies and recommendations that, when implemented, will reduce the incidence of problems and generally lessen the stress of transport. It is well known that respiratory disease can develop in horses during transport. However, other problems, such as injuries and colic, can also occur. In addition, prolonged transport is very tiring, a factor that may impair the horse's performance after arrival.
Jones: There are two ways in which we might view equine transport as a problem. The first is from the horse's perspective. Transport, other than using their own legs, has not been a factor for which horses have evolved. As a result, all of the unnatural elements of transport confinement, noxious air, motion, vibration, unexpected noises, etc. contribute to the potential for their being subjected to insults to their health or altering their physiology. These insults and alterations (e.g., decreased immune resistance due to stress) can potentially lead to disease, injury, or impaired performance. Some horses are clearly more affected by these factors than others, but for those that are affected, the problem can be severe.
From the veterinarian's perspective, transport-associated stress and disease are really difficult problems to understand completely. A fundamental issue is that horses are so variable in their responses to being transported that we do not actually know how prevalent the problems are. In turn, this variability makes it extremely difficult to clearly interpret the results of studies that try to determine what the primary factors associated with transport are that lead to health problems for the horse. Furthermore, there are so many variables that play a role in different transport situations type of vehicle, duration of trip, climate and season, history of horses, etc. that trying to define the "key" factors responsible for transport-associated problems is problematic.
Additionally, horses that are affected by being transported respond in widely varying degrees, from acute, life-threatening clinical disease to extremely mild effects that only the most sensitive tests can detect, or may even be undetectable by any conventional measure. All of these factors make transport-associated diseases a truly difficult problem to authoritatively address and about which to make recommendations based on scientific justification.
Robinson: It is very clear that transportation is associated with the onset of respiratory disease in some horses. In an epidemiological investigation conducted by the University of Illinois, transportation for greater than 500 miles was the greatest risk factor for development of pleuropneumonia. Investigators in Japan have also shown that transportation for more than 20 hours is associated with the onset of fever and pneumonia. Although respiratory problems are the best documented, other problems can occur.
Transport is a form of mild exercise akin to walking as the horse attempts to maintain its balance in a moving vehicle. Carry this out over several hours and you have a horse that arrives fatigued. It is often mixed with strange horses during and after transport and this has two effects on the horse. First, it is exposed to infectious agents to which it may not be immune and that could lead to disease. Second, it is socially stressed as it attempts to find its position in the new social hierarchy. The social stress and the exercise stress of transport are thought to have deleterious effects on the immune system which increase the susceptibility to disease.
What are the main issues that face horses and their owners regarding transportation?
Kohn: Everyone talks about "travel stress." We do not know exactly what constitutes travel stress for horses; however, we do have some ideas about what aspects of travel might pose a challenge for equine passengers. The travel environment is an important factor. The type of transport vehicle is probably important. There are many types of road transport vehicles available, ranging from small to very large. Horses may ride facing forward (most conventional small trailers), backwards or on a slant. During air journeys, the number of horses on each pallet may vary from as few as one (very expensive!) to four. Some planes transport people in one compartment and horses in another. The quality of air in the transport vehicle is important. Air in such confined spaces is soon contaminated with dust and mold particles from hay and straw, with fumes from urine, feces, and potentially with fumes from exhaust of other nearby vehicles. The efficiency of the ventilation system in the transport vehicle is, therefore, a critical factor in maintaining an optimum transport environment for the horse.
The horse's temperament is an important factor. There is a marked individual horse variation in response to transport. Some horses load quietly, and adjust quickly and well to transport. Others may be frightened or anxious during loading and transport. We suspect that prior experience with transport may help horses to remain calm and "unstressed" while traveling, but the issue of the possibly beneficial effects of accustoming horses to the rigors of travel requires further research. For horses that fly long distances, the issue of jet lag must be considered. Crossing time zones probably affects the normal circadian rhythms of the horse's body, just as transmeridian travel affects such rhythms in people. The effects of jet lag on horses have not yet been studied. For horses traveling to the Sydney Olympics from North and South America or the European Union, jet lag may be a factor.
Leadon: Our research here demonstrated that the majority of horses tolerates transport very well. So, that means there are horses that don't tolerate transport very well. What is the manifestation of their intolerance?
Oikawa: Transit-associated respiratory disease is a major problem in transporting horses. The mean incidence of the disease in racehorses belonging to the Japan Racing Association that were shipped below 1,000 km between 1993 and 1997 was 1.2%. Otherwise, in cases involving prolonged transport by road of over 1,000 km between 1989 and 1994, the incidence was 11.9%. These differences of values suggest an increased incidence of disease with increased transport distance and/or traveling time.
Jeffcott: What a lot of horse people don't appreciate is how seriously to take travel, even some of the shorter journeys. What I hope comes out from our meetings and research is that they consider what happens before traveling, as well as during traveling. They should plan what the journey is going to be like, and where they are going to stop, and how they are going to stop, and how they are going to manage the horses. They need to remember that no matter what the traveling was like, some sort of recovery period is going to be necessary.
It's important owners don't forget about the post-transport situation. If you insult a system such as the respiratory system, the horse can manage even though he is stressed. But if they are not given some sort of a recovery period, and they are stressed from the travel and the competition, and they are not monitored carefully, they could easily be in a situation that a little more exercise or competition could turn them over a little too far. That could mean a serious transit stress or pneumonia as a result of the cumulative effect of the transport and the competition and the traveling back home. If there is no possibility for proper management and rest periods during and after transport and competition, there will be cumulative effects.
A lot of our discussions at the workshop were about horses other than elite international horses. They were about all horses. If people are traveling every weekend and the horses are exercising during the week, then there probably is a cumulative effect. Because studies haven't been carried out, one is giving advice based on experience rather than scientific studies.
Allen: Every horse is going to be transported at some point, whether it's to a sale or to a competition or just across town. For road transport, the horse has to be loaded into a trailer which he has to be acclimated to do. The owner has to make sure the horse is not ill prior to transport. Crossing state or international lines requires health certificates and passports.
The problems that face these horses just keep piling up, depending on how far you are going and your mode of transportation. But even on the simplest trip, you have to get the horse in the trailer. You have to get him to ride suitably to the destination so he comes off the trailer unharmed. In the end, the horse has to go do whatever it was originally destined to do. If your horse is so stressed out and wringing wet by the time it arrives at a competition even a few miles away, you haven't accomplished much because the horse is not going to be able to go do his job.
Geor: The big health concern is respiratory disease, of which the worst example is pleuropneumonia. The severity of these cases of respiratory disease varies greatly. However, any case of respiratory disease is potentially serious. As well, even a mild case may prevent the horse from participating in a competitive event.
Injuries are another concern. It is has been suggested that injuries are more common in young horses and those not used to travel.
It also has been suggested that the incidence of colic increases following transport, and that feeding practices may influence the development of colic. However, this information is largely anecdotal, and epidemiological studies are needed to determine just how common these and other problems really are.
Another big concern among owners and trainers is whether a horse's athletic performance is affected by travel. In human athletes, it is well recognized that this tiring nature of prolonged travel can adversely affect athletic performance. Another factor is jet lag, when athletes are required to compete soon after travel that involves multiple time zone changes. Unfortunately, little is known regarding the effects of travel (land or air) on subsequent exercise performance in horses. Two major factors could contribute to sub-par performance following transport: 1) subclinical disease, e.g., mild respiratory disease that is not noticed, but which impairs exercise capacity; and 2) delayed recovery following long and/or arduous travel. Also, a combination of suboptimal food and water intake and large fluid losses during transport will result in substantial weight loss. This deficit may not be recovered for up to three to four days after arrival and might affect performance during this period.
Jones: Clearly, the owner's primary concern in transport is to get the horse from Point A to Point B, and for the horse to be able to function appropriately at the other end. Although the specific function for the horse at the end of its journey is quite variable to race, compete, breed, or simply change venue as a pet the horse can only achieve its potential in any capacity if it is unimpaired by the transport experience. If the horse is traveling to engage in extreme competition, in which victory may be determined by a difference in performance of a fraction of a percent, then even subtle effects of transport can be significant. For this reason, shippers must consider carefully the conditions to which they are subjecting their horse during shipment, and how the horse is managed to recover following transport.
The problems that transported horses experience run the gamut of health problems of horses. We have had horses arrive in a trailer at the Veterinary Medical Teaching Hospital in Davis that had died enroute due to carbon monoxide poisoning the exhaust from the vehicle had been directed into the trailer. Although colic, lacerations, and dehydration are all regularly seen, by far the most prevalent problem is respiratory disease, ranging from severe pneumonia to very mild infection.
Respiratory disease can be caused by direct infection from airborne pathogens or by opportunistic infection from microbes already present in the horse's respiratory system. The indirect effects of transport that are perceived as stress by the horse can lead to its having an inadequate immune response to ward off infections that it might normally overcome with no clinical response. Additionally, factors such as irritation caused by the environment in the transport vehicle (gases and particles in the air) and the inability to move the head normally and clear the airways by normal mechanisms (head tying) might well contribute to the development of respiratory disease ("shipping fever") in transported horses.
Robinson: Horse owners and trainers want their horses to arrive at their destination ready for the event. This begins with a horse being fit and healthy at the time it is loaded for transportation.
They want their animal to travel safely. This means 1) that loading must be conducted safely by experienced personnel; 2) that horses must not be able to injure each other; 3) that aggressive horses must be segregated from others; 4) that the environment in the vehicle must be optimal in terms of temperature, humidity, and pollutant levels; and 5) that horse's health should be monitored regularly and veterinary attention must be available when needed.
They want to prepare their animal for competition after arrival. After long trips overseas, this requires good facilities for rest and recuperation, regular health monitoring, and the availability of expert veterinary care.
Horse owners do not want delays en route. Paperwork for transportation must be completed with expert guidance. Owners might also want to find rest areas with stabling for overnight stops before beginning the road journey.
Focus on some of the problems that horses face when being transported, especially respiratory problems.
Kohn: The most common transport associated medical problem is respiratory disease, so called "shipping fever." Typical signs are fever, cough, nasal discharge, depression, and inappetence. Affected horses may exhibit some, all, or any combination of these signs. Signs may develop during the journey or up to two or three days after transport. We are currently focusing research on determining why horses have shipping fever. The transport environment may be a challenge environment for a horse's respiratory system. The enclosed, suboptimally ventilated space in the transport vehicle and contamination of the vehicle's air with respirable particles such as dust, bacteria, and fumes, are likely to be important contributing factors.
When restrained in a transport vehicle, horses are tied with their heads up for safety. This posture may compromise the ability of the horse to clear its airways of inhaled debris. Bacteria that inhabit the upper airways of the horse under normal circumstances may be translocated to the lower airway (lung) during travel. A bacterial infection in the lung could develop in part because impaired clearance mechanisms cannot effectively clear the airways of these bacteria. Understanding "shipping fever" will allow us to design strategies for the most effective treatment and for disease prevention.
Horses may face other problems during transport such as colic, dehydration, and weight loss.
Leadon: One of the ones brought to mind straightway is trauma. That trauma usually stems from some form of panic, resentment, or frenzy. In long-distance air transport, the incidence of trauma is less than one-half of 1%.
The other things that occur are the occasional colics and medical conditions that could occur anywhere at any time. The most significant problem associated with equine transport is, and always has been, transport-related respiratory disease.
Owners can minimize the risk of trauma by conditioning their horses by giving them prior exposure and by allowing them to become familiar with trailers. Fundamentally, it doesn't matter to horses if the vehicle has wheels or wings, it's still confinement and movement.
We have big animals in small spaces into which they are going to urinate, defecate, and exhale and generate other forms of environmental contaminations, such as dust from feed. Because they are confined for safety, they have to have their heads held high. The combination of what happens in confinement with their heads head in a high position is the source of predisposition to respiratory disease.
The incidence of respiratory disease on long-haul air flights was until the early or mid-1990s akin to the incidence we saw in ships at the turn of the century and ran at or around 6%.
Since the early 1990s, it is believed that the increased utilization and availability of so-called "air stables," which fully enclose horses, may be responsible for an apparent increase in the incidence of respiratory-related transport disease
Oikawa: Our experimental study was made based on the influence on the horse's health of purification of the air environment inside of the vehicle during 40 hours of transport. In this vehicle, hay was suspended in front of each horse (breathing zone) in the first group and the gradually accumulating droppings and urine in the straw bed were not removed.
In the second group, there was no suspended hay. Instead of hay, horses were fed a pelleted diet. Feces and urine were removed and washed out at each rest period. In summary, it was found that this method of purification of the vehicle's interior environment was effective in reducing stress during transport.
Jeffcott: An awful lot of the respiratory problems result from challenge to various parts of the respiratory system from either bad bedding, hay, straw, build-up of ammonia, or bad ventilation. So the principle worry we have as veterinarians is that if horses are allowed to recover, most will sort themselves out. But the natural defense mechanisms that keep the airways clear are in a bad situation a horse box with bad ventilation and too many fungal spores or bacteria. That situation is going to trigger a number of responses in the animal from inflammation right through to a serious pleuropneumonia. We as vets want to detect these problems early on to implement proper treatment.
Transporting stressed or sick or injured animals is even more dangerous than transporting normal ones.
Allen: We've known obviously for years and years that there is respiratory disease associated with transporting horses. It's not that it is a new topic, we are simply revisiting an old topic to see if we can bring some science to it. You get horses off the trailer and they put their head down and all of the sudden a tablespoon of gray goop runs out of their nose. That's telling you that it's an unnatural situation the way we are transporting the horse by putting its head up in that high-dust environment. We need to do whatever is possible to alleviate the situation so they don't go on and develop things like pneumonia and pleuropneumonia and accumulation of fluid in their chest.
Robinson: When the horse is being transported, it is in an enclosed box which is moving at speeds from 40 to 600 mph. In order to avoid injuries and to maximize the number of animals being transported, each horse has little room and little ability to move about. Horses are generally bedded and fed during transport, and the bedding and feed are a source of particulates that can initiate airway inflammation. The ventilation system may be inadequate to keep these particulates to tolerable levels. Although it is offered water, the horse may not drink adequately and become dehydrated. It is often exposed to other animals from a variety of sources with a variety of disease histories and so may be exposed to infectious agents (viruses or bacteria) to which it has not previously been exposed. It is also socially stressed by mixing with these strange animals.
If horses have to congregate at a site before international transportation, these same issues of strange horses, new infections, and different feed and water are all important. The horse may not eat, drink, or rest adequately, and this stresses its immune system and makes it susceptible to infectious agents. Recent exposure to virus-infected horses is another major factor determining susceptibility to pleuropneumonia.
Loading can lead to physical trauma to the horse, and occasionally injuries or illness can occur during transport. Changes in feed and feeding practices and reduced water intake may make the horse susceptible to colic.
On arrival, the horse may be tired, hungry, and dehydrated. Just as we want to get to our hotel rooms after an international flight, the horse needs rest. Often, however, it faces delays as quarantine regulations are fulfilled, and once again it is mixed with a new population and meets new surroundings and feeds.
What do we know about the physical aspects of transporting horses? Do we tie their heads or not, what do we feed them, how do we feed them, stops, fluid loss?
Kohn: Many horses are transported in two horse trailers in a tie stall. For safety, the horse must be tied with its head up. Some vehicles allow shipping in a box stall with the horse loose. When allowed to chose where to stand during transport, many horses will face backwards or on a slant. However, some horse prefer to ride facing front there is a large individual variation among horses and owners should get to know their own horses' preferences.
There has been little work on the most beneficial regimen for feeding horses while they travel. Conventional wisdom suggests that concentrates should not be fed because gastrointestinal motility may be slowed by confinement and grain-fed horses anecdotally are said to be more likely to develop colic. Provision of hay during the journey is desirable except that the hay is a source of particles in the air. Hay should be thoroughly soaked or high-moisture, low-dust products such as Haylage can be substituted. It is important not to change the horse's feeding program on the day of shipping, so introduction of haylage into the diet should be gradual. It is important to offer horses water every four hours or so during travel.
Leadon: Feeding is easy continuous access. Water the horses every six to eight hours, and water intake should be monitored. Feed them what they are used to eating, preferably roughage to give them activity. Boredom can result in self-inflicted traumas. I prefer a hay, but there is no reason it couldn't be a pelleted product. It just gives them something to do.
You have to tie the horse's head to comply with airline safety regulations, at least during take-off and landing.
Stops should not be unduly prolonged because of the environmental deterioration that occurs in any vehicle loaded with horses.
I have yet to see fluid or electrolyte deficits in transported horses unless they have become ill, provided they have been offered food and water every six to eight hours. I've seen no evidence of dehydration.
Weight loss can be fecal-related, not necessarily all fluid-related. And they can lose fluid without being dehydrated.
Jeffcott: We aren't trying to panic people. There certainly are lots of horses who travel lots of miles, and they do so perfectly satisfactorily. But this is an accident waiting to happen if people don't take it seriously.
We don't know what the prevalence of problems associated with horse transport is. We know it is a serious problem, but we haven't quantified it. By quantifying it, one is going to point to the specific problems. We know the respiratory system is susceptible, but what else? What about problems in short-road transport versus long-road transport compared to international air transport?
What are the risk factors? When you have a list of those major risk factors, the question will be which of those can you do something about? What are the indices of pending disease? What happens in other body systems, and when do they occur? Many of these problems are subclinical, and remain subclinical; but unless you do investigations, you aren't going to know they exist. And you aren't going to know their effect on the animal.
One of the things vets and owners say is horses are immunocompromised during transport, and that leads on to these other things. But, are horses that get pneumonia more compromised than others? We don't know.
We also don't know the effects of pre-transport conditioning. What should you do to your horse to make him better before transport to help him stand the pathophysiologic changes and the stress to the respiratory system?
Are there particular types of behavior that are associated with disease? Should you use sedatives before transport? Are they contraindicated because of some of the pharmacological effects they have? Do they affect the immune system?
Hydration status also is a question. Evidence is there are a number of horses who, when they travel, become dehydrated, and that can predispose them to other physiologic changes, which will predispose to shipping fever.
We aren't monitoring these horses effectively enough for hydration. Some horses are not properly hydrated when they leave home, and some horses because of conditions during the journey become dehydrated. That depends if horses are given the chance to drink during the journey, whether they will drink, or whether they are trained to drink. Some tubing or other administration of fluids could be necessary, and that is a veterinary decision. And, of course, on most journeys you don't have vets.
Allen: That was part of what the workshop was designed to focus on what's known but perhaps not well-circulated. We know that if we put their heads up and do not allow them to get their heads down, and we transport them for an extended amount of time, 10 hours plus, some horses will develop respiratory problems. There also are other problems like colic and lacerations, and all the things that horses are heir to. The major thing is respiratory challenge.
Geor: Updated recommendations regarding these issues will comprise a large part of the newly developed guidelines. There is much debate regarding whether the horse's head should be tied or not during transport. We have traditionally restrained the horse for reasons of safety. Certainly, safety remains a concern and, in the case of air travel, mandates the use of head restraint. Research in Australia has demonstrated that tying a horse's head for a lengthy period results in an increase in the numbers of bacteria in the lower respiratory tract. We as yet do not know whether this "head-up" position also leads to an increase in bacterial numbers when horses are transported. This issue is one that will receive a lot of attention in upcoming research.
The whole area of feeding is not well researched. However, because we know that dusty, moldy feeds increase risk of respiratory problems in any circumstance, it makes sense that these feeds should not be fed in the enclosed environment of a horse trailer/air box. So, what to feed -- good-quality hay that is soaked is a good choice. Grain feeding is more controversial; most will restrict (half amount fed) or stop grain feeding. Again, this is an issue that requires further research, but for now, the best advice is to restrict grain feeding during travel, but make roughage available. Bedding in trailers is another concern; straw bedding can be as bad or worse than hay with respect to dust. Rubber mats are a better option.
Taking steps to ensure that the horse maintains hydration is also important. Fluid losses can be substantial (up to 0.5% of body weight per hour). So, over a 12-hour period, the average-sized horse may lose 20kg or more as sweat and other "insensible" fluid losses. Horses need access to water on a regular basis during transport (at least every four to six hours).
Robinson: We know that horses have little freedom to move, and that they use muscular energy to maintain their posture.
The horse's environment is rich in particulates and the by-products of urine (ammonia) and feces (bacteria and endotoxin). These are often present at levels known to induce inflammation of the airways in humans and other species.
Temperature and humidity are rarely controlled in transport vehicles. While vehicles are in motion, forced ventilation through the slats and vents may keep the temperature tolerable, but if trailers are parked in the sun, the temperature inside the trailer rapidly increases. Humidity increases, too, because of the urine-soaked bedding. In aircraft, temperature is controlled during flight, but humidity is not. When aircraft are parked, temperature and humidity can increase rapidly. This leads to increased breathing, which delivers more of the deleterious material into the respiratory tract.
What is the impact of internal and external environment on travel?
Kohn: We recommend avoiding extreme cold or heat when shipping horses. During hot, humid weather, the environment inside the transport vehicle is likely to be even hotter and more humid than the ambient conditions. This is particularly true when road transport vehicles or airplanes are stationary, and ventilation is poor or non-existent. We know from our studies on heat and humidity before the Atlanta Olympics that a hot, humid environment imposes significant demands on the horse's thermoregulatory systems. To dissipate heat, horses sweat and increase their respiratory rates. Sweating may lead to dehydration. Therefore, during hot weather, it is prudent to consider traveling at night. Rest stops should be short, allowing only enough time to refuel, check the horses, and offer them water. It is important to select shipping rugs according to the ambient conditions. I have seen horses get off a van sweating under heavy rugs. When the owner left home, it was cold and the rug was appropriate, but temperatures increased during the day and, during the long journey, the blanket was inappropriately heavy.
Leadon: There is a clear need for further studies of environments that occur inside travel trailers and air stables and of the impact of these environments on equine respiratory health.
Jeffcott: We've been alerted as a result of the meeting that the air crates are something that seriously and rapidly need looking at, particularly in light of the Sydney Olympics. We hope to stimulate some discussions with the airlines about that. It's up to us to show there are problems and those could be improved if the design of the boxes were changed.
This does have serious financial implications for the airlines, and therefore it's not just a simple thing to say "here's how to do it better" and it will be implemented. We have to scientifically annotate that there are problems and they can be improved in this way.
Road travel is much more complicated. There are so many different kinds of transporting vehicles. We will come out with the recommendations that the vehicle be suitable for what it is doing, that it be carefully maintained and properly driven, and that the journey be carefully planned. Things that are common sense.
Allen: This is where it gets a little more complex. We know the environment obviously has an effect, but here is where there have not been a lot of scientific studies. You can go back to human studies in air carriers, and they know that people have to have a certain amount of fresh air in the cabin.
In an airplane, you have a concentrated number of people in a small space, so you have a lot of "things" floating around. Infectious diseases are circulating in that space. If you get on the plane with 400 of your "closest friends," you've increased your risk of getting a respiratory disease.
It's a little different with horses because of the feedstuffs and the amount of dusts and pollens associated with feedstuffs. Horses are going to have a lot of particulate matter in their air. We know that as we increase the amount of particulate matter and decrease the amount of air circulation, we're going to increase problems. We don't know where those critical cutoffs are.
We learned about critical cutoffs in Atlanta. We realized that relative humidity has basically no effect if the temperature is 75° or below. It is when the temperature is 75° or above that you get the effect. We need to know the same things about the amount of dust and particulate matter and air circulation in a trailer or a plane that we know about heat and humidity. And we need to know if the head up/head down situation is merely an interesting side-effect to this, or whether it is a critical factor.
There are a lot of good horsemen who have opinions, but in the final analysis, we don't have data.
In the heat and humidity studies, it was asked, "Can you really put cold water on the large muscles of the rump and croup?" Many, many experienced horsemen said no, but it turned out that you can very safely and effectively.
There are no doubt those same myths in transporting horses, but we have yet to uncover them.
Geor: As far as the internal environment is concerned, the most important factor is ventilation. Maintaining a horse within a small, poorly ventilated space is going to greatly increase the risk of respiratory disease. So, every attempt must be made to ensure that there is some airflow into the trailer, even if you think it is cold outside. If it's cold, put a rug on the horse.
Heat and humidity are the main external environmental factors. Problems with poor ventilation will be compounded in hot/humid conditions. In addition, the horse is likely to sweat more under such conditions, so water may have to be offered at more frequent intervals. Some consideration must be given to time of day for travel in hot conditions, the length of travel, and the frequency of rest stops (for access to water). Also remember the effects of transport from a cool to a hot climate; the horse should be allowed a period of at least seven days for acclimatization to the new climatic conditions.
Jones: We have insufficient information that has been objectively obtained to build an equine transport vehicle that is ideal for the horse. Similarly, we have insufficient knowledge to state with great certainty what constitutes ideal transport management, particularly given the number of variables that affect the horse, the differences in horses, and the practical constraints that are placed on shipping horses. Until we know what factors in the transport environment are most responsible for problems that the horse experiences, it is difficult to define what aspects of vehicle design are most important for minimizing the effects of transport on the health of the horse. These problems could range from poor air quality insulting the respiratory tract (ventilation) to vibration or noise causing stress that impairs the immune system.
Dr. Leadon's studies of the transport environment aboard jet aircraft certainly suggest that considerable benefits might be obtained with some fairly simple design changes to the containers in which the horses are housed during transport. Remarkably little work has been done to consider how we might modify road vehicle designs to minimize their effects on horses being transported.
These oversights include even simple things, e.g., where windows and vents are placed and how they affect ventilation, or whether different types of suspension systems result in vibration frequencies that cause physiological changes in horses, similar to the effects of road vibration on long-distance truck drivers.
A number of these factors should be considered in the design of equine transport vehicles, and hopefully as we obtain more data about what factors most affect the health of the horse, they will be.
Robinson: Horses are more stressed by heat than by cold. The big danger from the external environment is overheating of the transport vehicle, particularly when it is parked.
Inside the vehicle, particulates, ammonia, and endotoxins can all initiate airway inflammation. This is associated with mucus secretion and bronchospasm (constriction of the airways by smooth muscle).
The horse has little freedom to move and is forced to keep its head up, often directly in front of its hay source. The horse needs to lower its head regularly in order to keep its respiratory system healthy. Studies at the University of Sydney have clearly demonstrated the very large increase in bacterial numbers in the trachea when horses are prevented from lowering their heads. Within twelve hours, the number of bacteria increases 10,000 fold, and it takes eight hours of head freedom for the numbers to come down. As the number of bacteria increases, some horses develop fevers. This increase in bacterial numbers is in part a result of the reduction in the rate of mucus transport that occurs when the head is elevated. In the transported horse, dehydration and increased mucus production may exacerbate the problem.
Depending on its quality, hay may be the biggest source of air pollution in the transport vehicle. Keeping hay directly in front of the horse puts this particulate source directly in the horse's breathing zone (the space from which it takes in air). Studies from the University of California, Davis, have shown that the air in the trailer recycles back over the top of the horse, forward under its legs, and up in front of its face, most likely through the hay!
What needs research?
Kohn: We identified several main issues for research. We need to define further the types of disease problems and their frequency of occurrence during transport. To answer these questions, a large epidemiologic study is required. A great deal of work has already been done by the Japanese Racing Association. We hope to utilize their data base in a retrospective epidemiological study of these issues. As I mentioned previously, we are interested in why horses have shipping fever during or after transport; particularly, is the head up posture of horses restrained for transport an important contributing factor? We are interested in the design of transport vehicles and airstables. What is the optimum stocking density? It is especially expensive to fly horses, so having more horses per pallet is more economical, but what is best for horse welfare? There are many different road transport vehicles available. Design features of these vehicles should also be studied to optimize horse comfort. What are the effects of transport on performance? This is a particularly difficult issue to address because there are so many variables that affect performance. What are the effects of jet lag on horses? There are many questions that require focused study.
Oikawa: We need research to determine the biological effects of vibration and jolting. We need to clarify the cause and mechanisms of lower respiratory tract contamination associated with transport and to clarify the maximum limit in transport distance and/or traveling time. We need research to develop an easily identifiable and rapid diagnosis for transit-associated respiratory disease.
Other studies on transportation from JRA are as follows:
1) To establish an early diagnosis for equine respiratory disease by using ELISA to quantify equine pulmonary surfactant protein A, B, C, and D.
2) To base treatment of transit-associated respiratory disease on assesment of bronchoalveolar lavage.
3) To clarify the relationships between transport distance and/or traveling time and athletic performance ; a retrospective statistical analyses.
Jeffcott: I think that there is no question that the various aspects of the respiratory system need to be looked at. This is something that needs to be done by people who are experts in exercise and respiratory physiology.
The investigation of recovery is another area that needs research. How long do these changes persist? We hope to do this with some of the flights from the USA or the UK to Australia.
Another very important one we hope to get some data on is, "Does road transport actually affect the performance of horses?" The Japanese have done quite a bit of work on this, and we hope to get them to look at the records of the 33,000 horses they have monitored in the JRA database to see if we can relate duration of the journey with incidence of disease and racing performance. What length of journey affects performance?
The study of "air stables" in planes is necessary. We need to look at the respiratory system and injury during these traveling situations.
In the long-term, we need an epidemiological study to correlate the risk factors we have identified and know which ones we can modify.
The Olympics, we hope, is going to be the catalyst to get transportation research going, but it has repercussions far beyond that. I hope this will be a long-term effort involving many researchers in their own laboratories.
Allen: I think to get the respiratory studies done there are going to have to be simulators built that can simulate the conditions of travel. That way we can study horses in more of a laboratory setting rather than with all the shortcomings of being in a trailer or airbox. Simulators need to be built for both air and trailer transport.
Once the work gets started, we need to draw in appropriate members of the trailer and air transport industries and involve them in the process. At this point, this is a preliminary "think tank," and based on our experience with the heat and humidity studies, it's early to draw in the members of the industry.
We need to study the same basic premises as Atlanta. We'll start by studying the population and say here is the incidence of the problem and here is what is happening in the population of horses getting sick. Then we start asking scientific questions.
We need to know the critical amount of particulate matter. Is there an air flow scheme that will help? Can we face the horse in a certain direction that provides a dramatic decrease in respiratory problems? We know that airflow on the ground (planes sitting on runways) is a problem and that particulate matter skyrockets. Can we reduce the amount of time these horses are on the ground, or can we change the airflow on the ground or in the air?
When we can say, "If we change certain conditions, we can change the health of these horses, then we can make some final recommendations."
As we pull all that together, we finally will get some good science to back up a lot of good, common horse sense on transporting horses. We no longer will stand around in the corner of the barnyard and scratch our heads. We'll be able to say: "We know this, and here's how we can help these horses."
Heat and humidity were a huge issue, but we may not help horses in Minnesota that much because they may not deal with those issues unless they ship south. But we are going to help every horse in the world that gets into any sort of transport. That's why this is so important not only to get the answer, but get it right!
There isn't a lot of funding out there for this topic. This is a world-wide question and people tend to think it is someone else's problem. But it is everyone's problem. And every horse owner needs to encourage his or her breed and discipline to get involved and support this research. Those individuals or groups should feel free to contact any of us. We need help.
Geor: Several key areas were identified at the recent workshop, and these issues should form the basis for research over the next one to three years. Given the importance of respiratory problems in transported horses, we must focus on the factors that predispose to respiratory conditions. Specifically, how can trailer/air box design and other management factors (feeding, head up vs. head down, hydration) reduce the impact of the local environment on the respiratory system such that the risk of disease is greatly reduced.
Another area that will hopefully be addressed is recovery following transport. Should horses be rested following transport? If so, for how long? Would such recommendations apply to travel of any length or only for long haul transport?
Jones: As my earlier comments indicate, I think there is a fundamental need for us to understand what factors in the transport environment contribute the most to the development of transport-associated stress and disease in those horses prone to them. This will require studies in which we can factor out environmental variables from management variables from vehicle design variables from the variations in response of the individual horses. Different horses may be affected more by different factors. However, if broad generalizations emerge, they will define the targets for which we should first find solutions.
Additionally, we need to do more work of an engineering nature to better understand the ways in which the vehicles in which we transport horses create an environment that affects them physiologically, and to explore changes in design that will minimize the deleterious aspects of the transport environment. Then we can consider how to implement such changes practically and affordably!
An owner or trainer who is familiar with the horse may be sensitive to changes in its attitude when a veterinarian cannot measure anything that indicates a medical problem. Being sensitive to your horse's responses can be useful in determining how long the horse needs to recover from being transported prior to returning to work.
Robinson: Although we know that respiratory problems are of major concern, we know little of the incidence of colic or trauma.
In order to advise horse owners and trainers on the optimal management of the horse, we need to know how long it takes a horse to recover from an international flight or a long road trip. Horses will suffer jet lag just as people do, and it will take days for their circadian rhythm to be restored.
The environment inside the vehicle needs lots of study. What is optimal trailer design to maintain a flow of fresh air through the trailer and keep particulate levels low? What is the best suspension to minimize the work required to maintain balance? What is the best transportation container (air stable) for international transport and how many horses should be in each container?
Next we need to study the response of the horse to transport. How short a rest period is required and how often are they needed to prevent bacterial accumulation? What is the impact of dehydration and inflammation on mucus clearability, and how can we change this? Why do certain bacteria that normally reside in the nose and throat (such as Streptococcus zooepidemicus) colonize the lung when the horse is transported or prevented from lowering its head? What is the effect of transit stress on immune responses?
It is important to realize that most horses tolerate transport very well. We need to identify important risk factors and how those can be reduced. Because of limited resources, we may never know specifically how these risk factors initiate disease in the horse. However, we must use the extensive knowledge available from other species and apply it for the benefit of the horse.
About the Author
Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.
POLL: University Equine Hospitals