Acclimating Competition Horses

The whole world is a stage, it has been said. And so it is for horses. Equine transportation from one part of the world to another for competition in days gone by generally was restricted to Olympic events once every four years. But that is a far cry from today, when horses by the dozen move from one country to another to compete in eventing, dressage, jumping, racing, cutting, and reining. Other horses are purchased at sales in this country and sent to new homes in Europe, Japan, and points in between. European sport horses are purchased and shipped to the United States. Plus, there is the matter of shuttling stallions, with horses traveling to places like Australia after spending a breeding season in the United States, England, or Ireland.

There is not that much concern about stallions acclimating because they aren't facing an immediate arduous physical challenge upon arrival. But what about the event horse or racehorses, for example? They travel through time zones, from low elevations to high altitudes, and vice versa. How can they acclimate quickly and be ready for competition? Perhaps the more appropriate question is: Can they truly acclimate and perform at their highest level of ability?

The answer would seem to be yes, but there are a great many unanswered questions despite years of study.

In this article, we'll take a look at studies involving equine jet lag being conducted today at the University of Kentucky, and we'll revisit some of the research that was launched in the mid-1980s in Ireland and elsewhere. Along the way, we'll pay a visit to Joseph O'Dea, DVM, of New York, a former president of the American Association of Equine Practitioners (AAEP) and the veterinarian for a number of years for the United States Equestrian Olympic teams. Information from O'Dea comes both from personal interviews and his book Olympic Vet.

Changes in Latitude

There are some physiological assets that help the horse acclimate from one elevation to another. Equine exercise physiologists tell us that the horse is unique in that it stores red blood cells--which carry oxygen through the bloodstream--in its spleen. When the horse is challenged by exertion, including performing at high altitude, the spleen contracts and more oxygen-carrying red blood cells are released.

Trail riders who travel from a low altitude to 10,000 feet or more have experienced this firsthand. If they dismount and hike up a steep slope, they normally will be gasping for air very quickly. The horse, meanwhile, can carry a rider up the same grade with its body doing a much better job of supplying the needed oxygen.

Unfortunately, providing an increased supply of red blood cells is not a cure-all when horses are asked to acclimate to new elevations and changed time zones. There are other stress factors involved.

O'Dea recalls one of the early concerns with acclimation for the United States Equestrian Olympic teams in 1955, when the Pan Am Games were held in Mexico City at an altitude of about 8,000 feet above sea level. Although he wasn't involved with that team, he had heard reports concerning acclimation problems for the eventers, jumpers, and dressage horses.

As a result, when the Olympics were held in Mexico City in 1968, O'Dea, as head of the veterinary team caring for the U.S. horses, decided precautionary action should be taken.

In Olympic Vet, he had this to say concerning what happens when there is a marked change from low to high altitude:

"When the animal body is transported to higher altitude, it experiences physiologic changes, the duration of which is commensurate with the degree (height) of change. At high altitude, there is less oxygen and lower atmospheric pressure. Both factors result in lowering of the ability of the animal's body to absorb oxygen, resulting in insufficient oxygen to meet the animal's needs.

"In order to adjust for the lowered oxygen absorption, the body works to increase the solid oxygen-carrying component of the circulating blood called hemoglobin by tapping the splenic reserves and by lowering the related fluid component. Due to the decreased intake of oxygen and the lowering of the gaseous exchange in the lung, more than the usual amount of carbon dioxide is retained in the blood and body tissues. The buildup of carbon dioxide stimulates the respiratory center, increasing the respiratory rate. Our clinical evidence in the horse revealed that the stress of altitude and the altered chemical state effects an increase in urine output (an enzyme response), which assists in lowering the fluid component of the blood, thereby effecting a relatively higher level of the hemoglobin-rich red blood cells (RBC). The resultant rise in the RBC concentration increases the oxygen-carrying capacity of the blood and serves to bring the respiration and gaseous exchanges closer to normal.

"In time, other body adjustment mechanisms come into play and the body reaches a state which permits normal activity at higher altitude."

The approach in 1968, O'Dea said, was to take blood samples while the horses were headquartered in New Jersey--about 835 feet above sea level--before making the trip to Mexico City. The blood test recorded the packed cell volume (PCV) of the blood--a measurement of the relationship of solid blood component (cells) to fluid blood component (serum). Periodic checks of blood samples were made after the horses arrived in Mexico City and compared with the initial measurement in an effort to determine how quickly horses were acclimating by utilizing an increased number of red blood cells.

It was found, O'Dea said, that the concentration of cells peaked an average of 16 hours after arrival at the higher altitude, and receded during a comparable period, before plateauing at a level 12-15% higher than the normal PCV reading in New Jersey. The higher percentage of blood cells was an indication that the horse had acclimated, or at least was acclimating, to the higher altitude.

The horses, O'Dea reported, were walked in hand during the first two or three days after arrival while acclimating and were allowed to begin work under saddle on the third or fourth day, depending on the individual.

The approach apparently worked for the United States contingent. The three-day event team won the silver, Michael Page won the individual bronze in eventing, and Bill Steinkraus, riding Snowbound, won the individual gold medal in jumping.

Some of the teams from other countries failed to take precautions with altitude adjustment, O'Dea said in his book, and "more than a few horses suffered from hypoxia, colic-like symptoms, prostration, and physiologic disturbance."

More strides in determining what happens when horses are transported from one country to another began in the late 1980s with funding from the Federation Equestre Internationale (FEI), the governing organization for Olympic level equine competition.

One of the research facilities involved in that effort was the Irish Equine Centre in Johnstown, Naas, County Kildare, Ireland, which was founded in 1984.

Long-Distance Travel

Then and today, one of the leaders in the research to understand transport stress and the horse's ability to acclimate after long-distance travel has been Des Leadon, MA, MVB, FRCVS, RCVS, head of clinical pathology and clinical services at the Irish Equine Centre. One of the goals of the research was to collect blood samples from horses transported long distances. The blood samples, when tested, formed a virtual data bank against which other samples could be compared, providing parameters to indicate when the horse had become acclimated to its new environment.

Taking the blood samples was only one part of the research. Body weight was recorded before and after trips, and the horses were monitored for respiratory and other ailments. There has been a steady accumulation of data through the years from research around the world, including recent studies at the University of California, Davis. These studies provide a better understanding of what happens within the equine body during transport.

Leadon reported on the early research at the 1991 annual meeting of the Association of Equine Sports Medicine in Reno, Nev., as well as in an interview at the time with this writer. He talked further on the subject in an interview more recently that was posted on the Irish Equine Centre website.

When the research was launched in the mid-80s, Leadon says, there was little information on the effects of long-term transport, other than that a certain number of horses became ill. "We focused initially on the types of illness that occurred and tried to identify those illnesses that we might be able to do something about," he said.

It was soon discovered that air movement, or lack of it, could have a profound bearing on a horse's good health during transport. Leadon put it this way in the posted interview:

"It doesn't make any difference whether you are transporting horses by road or by air. Effectively you are putting them into a tube--whether it is an aluminum tube or a wooden tube, and whether it has wheels or wings, makes very little difference to the environment in which the horses are transported. When horses are stabled, there is a general recommendation that we try to achieve air exchange within their immediate environment three times every hour. When you have jet airplanes traveling at speed, we can achieve air exchange three times a minute. When we transport horses by lorry (motorized vehicle), we can achieve quite frequent air exchange. The difficulty with both methods of transport is that once the vehicle is stationary, there is an immediate deterioration in the quality of the air.

"So the primary problem for us to address is how to make sure the environment is as clean and as favorable as possible to the horses," Leadon continues. "The thing that we worry about most is pre-existing respiratory disease. If the airways are compromised prior to transport and horses are sick when they get on a vehicle, we can be pretty confident they are going to be even more sick when they get off."

And, it goes without saying, a sick horse is going to have a difficult time acclimating to a new environment, be it a different time zone or a different altitude.

Circadian Waves

Next, we come to traveling through time zones and what effect this might have on a horse's ability to acclimate. Humans suffer jet lag, a sort of malaise, when traveling through multiple time zones. It appears horses do as well. As humans, we must acclimate to the time change, and so must horses.

Barbara Murphy, graduate research assistant at the University of Kentucky's Gluck Equine Research Center, University of Kentucky, reported in the October 2004 issue of Equine Disease Quarterly on what had been uncovered by research at Gluck.

All mammals, she reported in her opening remarks, possess a "master" circadian clock that resides in a specific part of the brain.

"Here," she stated, "diverse physiological processes, such as blood pressure, heart rate, wakefulness, hormone secretion, metabolism, and body temperature, are regulated. Each of these processes is in turn affected by time of day. During daylight hours, the eye perceives light, and the light signals travel to the brain where they activate a number of important genes. These 'clock' genes are responsible for relaying signals conveying the time of day information to the rest of the body. Jet lag results in the acute disruption of each of these processes."

When jet lag occurs, Murphy reported, it has been found that human athletes do not perform as well during the first few days after arrival as they had prior to the trip. In one study, she said, it was found that times for a 270-meter sprint and 2.8 kilometer run were slower during the first four days after an eastward journey across six time zones. It is assumed the same would be true for the performing horse.

However, Murphy says, it is possible that the negative effects of jet lag can be ameliorated in horses.

"Feeding schedules," she maintains, "play an important role in ingraining biological clocks in studies carried out in rodents, particularly within the digestive system. From this we can surmise that it is important to change both feeding times and exercise schedules to mimic the new time zone prior to travel in order to shorten the amount of time required for resynchronization of digestive function and performance capacity upon arrival.

"Lighting is also of paramount importance," she states. "Based on results from human studies, exposing animals to bright early morning light for several days prior to an eastward journey across multiple time zones--or extended hours of evening light prior to a westward journey--will help synchronize circadian rhythms to the new time zone prior to travel."

Murphy also points out that the number of time zones crossed can be significant. "For example," she said, "a flight from Britain to the East Coast of the United States, across six time zones, would require a significantly greater resynchronization time than a flight from the East Cost to the West Coast (three time zones) within the continental United States."

Take-Home Message

It becomes obvious that acclimating to a new environment is a challenge for the competing horse, involving everything from wellness and altitude to circadian rhythms involving time zones. It also becomes obvious, based on research, that there is no quick fix. It takes time to acclimate.

"The circadian clock can only adapt to a new lighting schedule gradually," says Murphy, "and while the brain receives the light information directly, there is a further lag period involved in transmitting the time of day message to peripheral tissues."

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at or by calling 800/582-5604.

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