Page 108 - Speedhorse August 2018

The fastest way to cool an overheated horse is with cool/cold water, applying it over the body, especially on areas where the blood is near the skin surface such as the neck, chest, belly and legs.
If you don’t have air conditioning in the trailer, you might pull into a gas station peri- odically and use a hose with a spray/mister on the end of it to dampen the horses with water, or use a sprayer bottle as a mister to spray on tolerant horses. This will help keep them cool and give their sweating mechanism a break. Any moisture that evaporates will help.
“A study I did several years ago showed that horses lose a fair amount of weight during transport, mainly from dehydration. One horse lost 77 pounds on a 450-mile trip, and it wasn’t even a very hot day. Outdoor temperatures were in the 80’s and 90’s,” he says. Horses aren’t drinking when they are in a trailer, and very few people stop and water their horses during a trip. Meanwhile, the horse is sweating, losing body fluid, and not replenishing it. He will suffer more stress, weight loss and fatigue if he is unaccustomed to traveling and nervous and upset during all those hours in a trailer.
Allen says the most common problem when hauling horses is overheating in the trailer. “A fair amount of those problems are made by us due to the common misconcep- tion that you need to put rugs on horses to keep them warm during a trip. If weather is a bit cool, people seem to want to blanket the horses, and they may overheat,” he says.
“Traveling by itself tends to dehydrate
a horse. They usually don’t drink much while traveling. If they are on a plane, they dehydrate just like humans do because of the altitude, etc. Make every effort to get your
horse hydrated before a trip, and then do your best to get him to drink along the way, which can be challenging.”
To get them hydrated before they travel, some horses that are being transported by plane will receive IV fluids before they go. Other horses can receive salt before a trip that is mixed in their feed to encourage them to drink. “You have to do this far enough ahead that they will drink before you go, and stop any salt at least six hours before the trip,” explains Allen. You don’t want them to have excess salt without access to water, because this will make them more dehydrated as body fluids are pulled into the gut.
“During transport, you should always try to keep horses cool if you can. Any time you stop, offer water and hope they will drink,” says Allen.
EXERTION CREATES HEAT
Exercise warms the body, and this is why horses like to run and buck on a cold day to warm up. “Muscle contraction is an ineffi- cient process. Muscles create heat when they are working. Of every 1,000 calories utilized while exercising, only 200 calories (20% of that fuel) is used to create motion,” says Foss. The other 80% generates heat as the fuel is “burned” during the chemical reactions that turn energy into movement.
“Thus, 80% of the energy is lost as heat that the body has to get rid of. Generating all that heat on a hot day can lead to problems. To illustrate how much heat the working mus- cles can produce, a horse will generate enough heat during a 100-mile endurance ride to melt 25 gallons of ice and bring it to a boil.”
A racehorse isn’t traveling 100 miles, but he is traveling at maximum speed for a shorter distance, which also generates a lot of heat. “Studies have recorded temperatures as high as 113 degrees in hard-working muscles. That’s hot enough to ‘cook’ them. If this
isn’t quickly reversed, there could be perma- nent damage. This could be a problem for racehorses because they are exerting at their maximum without much chance of cooling until they are finished running,” he says.
“Hopefully, the heat is removed from the muscles afterward in a short period of time. If the heat is not dissipated, core body temperature also rises and sustained rectal temperature of 108 can cause serious problems. If the brain gets too hot, the horse will have seizures and much more severe signs than simple heat stress. If this occurs, you are approaching serious damage that may be fatal.” This is heat stroke and the horse may collapse and have seizures.
The term heat exhaustion is often used when a horse is obviously exhausted and dehy- drated from overheating. The term heat stroke
MEASURING
BODY TEMPERATURE
The core temperature is in the core
of the body. In the past, the only way this could be measured was to put
a catheter near the heart. The core temperature is usually a degree or two higher than the rectal temperature. Intramuscular temperature is also a lit- tle higher than the rectal temperature.
The rectal temperature is easiest to check and the most practical. Even though it is always an under- estimation of the core temperature, everything is relative. If rectal tem- perature is what you are consistently using, it all ends up the same. Today, there are some sensors that resemble a big lozenge that can be put into
the horse. These are sometimes used in human athletes to measure core temperature. The animal swallows this sensor and it eventually passes on out through the digestive tract. This will effectively measure core temperature, particularly once it gets back in the small intestine. In that location, there won’t be anything to skew the reading, such as cold water coming into the stomach when the horse drinks.
106 SPEEDHORSE, August 2018
EQUINE HEALTH