July 2010, 

Hi Folks,  

     This year’s summer heat and humidity is stifling.  My horses are sweating just standing out in the pasture grazing. Because of the heat we're seeing in this area, I wanted to reprint an article taken from the Eastern Draft Horse Association…..  I’d also like to Thank Dr Ed Murray for reviewing this article for me. Dr Ed Murray felt that the only problem they didn't address were the issues from heat stroke that can also arise 2-3 days later after folks think all is behind them.   

Heat Stress/ Heat Stroke
 
     Summertime can be an extremely dangerous time for horses, especially if their owners aren't aware of the dangers in overheating...or "Heat Stress", when the condition progresses, it can lead to a life-threatening condition called "Heat Stroke". The best prevention for equine owners is to know how to identify heat stress in a horse before it progresses to heat stroke. If a horse is being exercised on hot days, extra care and attention must be given because there is a significant increase in the amount of heat produced by working muscles. Heat production can increase as much as 50% during intense exercise as compared with heat production when the horse is at rest. A horse increases its sweating rate to move more blood to the capillaries under the skin and breaths much harder in an effort to release this build-up of heat. The most commonly observed signs of "Heat Stress" are profuse sweating, rapid breathing, and a rapid heart rate. Some horses have a condition leaving them little or no ability to produce sweat; these horses are called "Anhydrotic". Since heat loss is mainly dependent on sweating and its evaporation, anhydrotic horses are prime candidates for heat stress. It's important to know if your horse falls at risk due to this condition, and take proper precautions to protect it from overheating. When you work or exercise your horse in hot weather, watch carefully for the signs of "Heat Stroke" which can include; skin that is dry and hot, a pulse and respiratory rates much higher than normal and unusually high rectal temperatures. "Heat stroke is life threatening," If you suspect that your horse is suffering from heat stroke, call your veterinarian immediately! While you are waiting for your vet, move the horse to a shady area with fans or wind to provide cool ventilation. Spray cool water on the horse’s legs and body to help lower the internal temperature. In critical situations, ice packs or cold water soaked towels should be placed on legs and other areas that exhibit large veins surfaced on the horse. (If cold towels are used, make sure to change them often because the horse’s extreme heat will quickly turn the cold water hot) Normally, a horse's rectal temperature is around 101 degrees Fahrenheit, if the rectal temperature is around 104 degrees for any length of time, it is characteristic of a life-threatening situation. When a horse is suffering from heat stress, stop working the horse and begin cooling the animal's body with fans and shade to help stop the onset of heat stroke. Also, pay careful attention to make sure that the horse doesn't become dehydrated during long bouts of exercise, large amounts of fluid can be lost through sweat. In most cases, horses should be allowed to drink as often as they desire, even during exercise, unless they are showing signs of heat stress. A "hot" horse has the chance to colic if given lots of water while they are hot. Small amounts of water should be offered to the horse in frequent intervals before, during and after exercise. A simple test that can be used to determine marginal water loss in a horse is the pinch test. When a section of skin on the neck or shoulder is pinched, the skin recoil will be immediate in normally hydrated horses. Dehydration will delay skin recoil. It is important to make sure the horse is properly cooled-down following exercise work-outs. The built up heat must be released from the horse's body through respiration and sweat. Heat loss through sweat requires moving air and evaporation. Walking a hot horse allows the air movement to continue to help evaporate heat, if left standing still; the lack of air movement could force the internal temperature to rise even higher. Air flow is vital to remove heat off the horse's body. The length of cool-down will depend on the amount of work, the environmental conditions and the individual horse. Horse owners, who know the signs of heat stress in horses can help prevent heat stroke in their animals, so becoming aware, can reduce the chance of injury, or even worse, death. If you use common sense and good judgment, this all can be avoided, so watch for the signs!
 
Managing Heat Stress in Horses

Kevin H. Kline, PhD, Professor of Animal Sciences

     As summer approaches, and the weather heats up, so does the competitive season for horse shows, racing and other equine event. This is the time of the year that severe heat-related stress occurs in equine athletes. Symptoms such as reduced skin elasticity and capillary refill time, anhidrosis (failure of the sweat glands), colic due to decreased water content of digesta, and hyperthermia may all be due to heat-induced disruption of the horse's normal water and electrolyte balance. Many horse owners don't realize that only about 25% of the energy used in the performance horse's working muscles is converted to actual muscle movement. The remaining 75% loss of efficiency is represented by waste heat that becomes very difficult for the horse to dissipate in hot and humid weather.
Unfortunately, the problems described above are often partly brought on by poor management due to some common misconceptions among horse owners and trainers. Several of the following misguided ideas have been found in equine publications of years past:

1. "Never let a hot horse drink more than one or two swallows of water at a time".

2. "Never give ice-cold water to a hot horse - either inside or out".

3. "Never let a hot horse cool out without a blanket or sheet".

4. "Never let a hot horse cool out in a drafty area".

     Each of the above disproven practices severely restricts the overheated horse's ability to dissipate heat the way nature intended. The immediate need for performance horses to rid themselves of highly detrimental waste heat is accomplished through four main routes. These include evaporation, convection, conduction, and radiation.
By far, the most important mechanism for heat dissipation in horses is evaporation. Conversion of the water in sweat (or other sources of water placed on the horse's hot skin) into gas consumes heat and cools the horse's skin. During and after exercise, the horse's skin is laden with dilated capillaries carrying overheated blood from the body core. The blood in these capillaries is cooled to help maintain a reasonable body temperature that will allow the horse's nervous and muscular systems to function normally. Even a normally hydrated horse with no inhibition of evaporative cooling that is exercising in a hot and humid environment may achieve a rectal temperature in excess of 104 degrees Fahrenheit. Disallowing the adequate water consumption that can be used for sweating, or blocking the evaporation of water from the skin using a blanket, are very bad ideas during hot and humid conditions. These practices can result in a horse's body temperature spiking into a dangerous range of up to 107 or 108 degrees Fahrenheit (heat stroke). Although allowing a hot horse to consume unrestricted amounts of water may lead to problems such as colic due to hyper distension of the stomach, it should be realized that a typical horse's stomach can hold between 2 and 4 gallons of fluid without being distended. So, even though a horse's stomach is small compared to other animals of its size, one or two sips of water at a time is overly restrictive when the hot horse is rapidly losing water trying to keep itself cool.

     Statement #2 above has been the source of some controversy over the years because of the belief among certain horse trainers that ice cold water placed on a hot horse's body will "shock" the horse's thermoregulatory system into shutting down blood flow to the skin. This belief has been found to be wrong. Extensive research conducted during 1995 at the University of Illinois and University of Guelph and at the 1996 Olympic Summer Games in Atlanta proved conclusively that horses working under hot and humid conditions were better able to maintain core body temperature within an acceptable range or even reduce it during rest periods after intense phases when ice water baths were used. Liberal application of icy cold water to overheated horses helps to dissipate heat not only by providing more water to evaporate from the skin, but also by direct conduction of the horse's body heat into the water which runs off the horse, carrying away excess heat in the process. According to University of Illinois researcher Dr. Jonathan Foreman, "In our treadmill simulations of C Halt (a rest period during a phase of the equestrian competitions at the Olympic Games), cold water baths were used with significant decreases in core temperatures and heart rates. No adverse clinical effects were apparent during the remainder of Phase C trotting or after exercise. Horses actually trotted more freely after bathing stops."
Standardbred trainers are probably the worst at helping their horses to thermo regulate between multiple heats on hot and humid days. The Standardbred training traditions of blanketing, limiting water intake and refusing to apply cold water to horses may severely limit the horse's ability to return its body temperature to near normal before the second heat is contested.

     Another practice that makes little sense physiologically is preventing access to moving air during hot and humid conditions. During the 1996 Atlanta Olympic Games, 85 misting fans were placed at shaded recovery areas throughout various phases of the equestrian courses to allow these elite athletes to stabilize and lower their body temperatures. Regular dry fans work to both increase evaporation, and also dissipate heat by the cooling process known as convection. Misting fans take advantage of the additional cooling property of blowing water onto the horse that is in the process of changing from liquid to gas. The shaded areas guard against additional heat load through solar radiation. Although radiation of heat from the horse's body into the atmosphere is a potential mode of heat dissipation, it most often works in the opposite direction during sunny days, with horses (especially dark ones) gaining radiant heat from the environment.

     In the battle against heat stress in performance horses, trainers should take advantage of all available modes of heat dissipation during hot and humid conditions. Making certain that horses are adequately hydrated before exercising in hot and humid conditions and providing as much water as possible between bouts of exercise is an important strategy for maintaining the critical sweating mechanism. Realistically, only a portion of the fluid losses incurred during long term exercise in hot and humid conditions can be replaced immediately. However, providing plenty of electrolyte-rich, high quality hay and fortified grain along with free-choice trace mineralized salt and water in the days after intense exercise should fully replace both the fluid and electrolyte losses. Additionally, taking advantage of conductive heat loss through cold water baths, convective heat loss through fans and natural air movements and avoiding radiant heat gain through the use of shade are effective methods to minimize the chances of excessive heat stress in performance horses during hot and humid conditions

Other News    

     Please mark your calendars for the upcoming Region 9 Show in Murfreesboro Tennessee, August 13 - 15, 2010. Check out our web-site for more information.  ALQHA will need volunteers to work throughout the day on Saturday (14th).  Please contact Beverly Davis  ( bldavis6@charter.net ) to let her know if / when you can be available to help out. This money ALQHA get from working this show helps pay for (among other things) our Banquet, end of year awards, and this newsletter.

Some interesting information from AQHA:

Alabama’s Quarter Horse 2009 population – 58,816 (down 874 from 2008) / Total Quarter Horses in U.S. – 2,758,654 (down 62,518 from 2008)

Alabama Quarter Horse Foals Registered in 2009 – 1,634 (down 413) / Total AQHA foals registered 93,835 (down 22,144 from 2008)

AQHA members in Alabama  - 2,857  /  529 are Amateurs  /  428 are Youth members BUT there are 15,486 Quarter Horse owners in Alabama…..

Whether you’re in the practice pen or the show ring, don’t let the upcoming summer heat and humidity get the best of you or your horse. Take care, have safe travels, and we here at ALQHA look forward to seeing you at all of the ALQHA approved shows throughout the 2010 year.

Donna Casey
Alabama Quarter Horse President