Heat Stress in Horses

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Written By Dr. Kris Hiney

How to cope so that summer is great for both of you!

As we approach the hottest part of the summer, it is important to review some basic strategies that will help us avoid heat stress in horses.  Often it is the summer months where we get the most enjoyment from spending time with our horses, but it is our job to make sure that we don’t overdo it with them.

So what conditions might make our horses over heat? Obviously high environment temperatures are the key, but also prolonged or intense exercise, or inadequate hydration may all contribute to heat stress.  Horses, just like us, dissipate the majority of their excess body heat through sweating.  Horses have a tremendous ability to sweat, and can sweat as much as 10-12 liters per hour.  Depending on the environmental temperature and the work load, it is possible for horses to become dehydrated in as little as 2-3 hours.  Horses that have inadequate access to water will not be able to sustain the same sweating rate as a horse with proper hydration.  For tips on water intake in horses please see Optimization of Your Horse’s Water Intake.  Horses also physiologically don’t help themselves out when it comes to hydration.  When we sweat, our sweat is hypotonic, or has less electrolytes in it, than does our blood.  Horses on the other hand, have either isotonic (the same) or hypertonic (more electrolytes) than does their blood. This allows horses to sustain sweating rates longer than we can.  So what does that matter? It is  the increase in tonicity of the blood through fluid loss that drives thirst.  As horse’s blood does not increase in electrolyte concentration with sweat loss, they may not have the natural stimulus for thirst.  Therefore a dehydrated horse may not actually drink when offered water. 

So when is it important to back off from activity with your horse?  Always think about both the temperature and the humidity.  Adding these two values together provides the heat index.  Horses will cool themselves normally, providing a normal hydration state and avoiding fatigue, if the heat index is below 130.  Conditions above a heat index of 150, such as 90 degrees Fahrenheit with 60% humidity, require more assistance in cooling.  With a heat index above 170, you might want to consider doing something else instead!  These conditions could be dangerous for both your horse and you!  Maybe consider watching a training video instead and give your horse a break.  If you have to ride, consider setting your alarm clock for the early morning hours or late in the evening.  More importantly, if you have to haul a long distance, it may be better to drive at night.  Trailers may often have inadequate ventilation to keep your horse cool.  In addition, the muscular work of balancing puts an additional heat load on the horse.  If you are considering a night trip, make sure that you are capable of driving at night or consider a good audio book to keep you awake.  It is important that everyone arrives at their destination safely.

Now, let’s say that we are going to ride and there is a heat index of 145.  What can you do to provide assistance to the horse for cooling?  Obviously we need to carefully monitor our horse throughout activity.  But we can help actively cool our horse through the  four ways animals to exchange heat: through the process of radiation, conduction, convection and evaporation.  Sweating obviously employs evaporation as a major way for the horse to dissipate heat.  Clearly a well hydrated horse is necessary to maintain stable sweating rates to dissipate thermal load.  But the environment plays a great role in how effective evaporative cooling may be.  High humidity levels will limit evaporation, which is why paying attention to the heat index is so key.  Water applied to the horse can greatly aid in cooling as it evaporates off the horse’s body.  Applying cool (not cold) water to areas which have large blood vessels near the surface of the body is the most effective.  Blood will cool as it passes through these areas and then return to the trunk of the body to help dissipate the heat load.   These areas include the legs of the horse and the neck of the horse.  The major blood vessels in the horse’s leg lie to the inside, so pay more attention to applying water to these areas. Continual application of cool water will prevent the warming of the water on the surface of the horses’ skin.  Otherwise, use a scraper to remove the warmed water and increase the rate of evaporative cooling.

Convection is another major way that an animal loses heat.  Convection simply is the heat that is lost due to air movement.  If you think about wind chill factors in the winter you can easily see how effective wind is in cooling!  Supplying fans or keeping the horse in an area with wind flow is ideal.  Misters with fans are often used in dairies in aiding with cow comfort, combining these effective cooling techniques.  If humidity is not high, these are fantastic methods to keep horses cool.  Fans with higher velocities will also provide more effective cooling.  If you live in a hot climate and have access to electricity, putting a fan near the arena will aid in cooling during rest periods.  Always make sure that your horse’s rate and respiration rate have dropped before returning to work.

We often think of radiation as a way to add heat to a system, but radiation simply means heat transfer through space.  The sun adding heat to the horse is an example of radiant heating.  We can avoid additional heat load by keeping the horse in the shade or riding in shaded areas.  The horse can also transfer its heat through space to any object that is cooler that it is.  While not practical, horses standing next to ice blocks would be radiating heat to the block.  However, standing under trees allows the horse to radiate some heat up to the leaves of the tree which are continually cooled by their own evaporation. 

Finally, the last method of heat transfer is through conduction, or the direct transfer of heat between objects of differing temperatures.  An example of conductive cooling would be a dog lying on a cooling mat or digging into the cool earth.  Any surface that is cooler than the horse that its body is in direct contact with will aid in cooling.  This is why cool water applied to the horse’s body helps to cool it. Remember the key is that the water is cool, not cold.  Cold water can actually result in vasoconstriction which can limit blood flow to the horse’s skin.  If a continual supply of water isn’t available, placing cool wet towels on the horse’s body would be an example of conductive cooling.  However, continual reapplication of cool towels is necessary as the horse’s body heat is transferred to the towels.

Next month we will discuss conditioning programs to prepare our horses for work in the heat, as well as dietary adaptations that may keep them cool.

 

 

 

 

Optimization of Your Horse’s Water Intake

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Written By Dr. Kris Hiney

Last month we discussed your horse’s water requirements and what factors may influence those requirements. This month we will discuss the best management techniques available to fulfill those water needs. Remember that water needs will vary greatly according to diet, temperature and amount of exercise. But ensuring that the horse consumes adequate water may not be as easy as we think.

First of all, we should consider the manner in which we provide water to the horse. If we remember where a horse naturally would drink water (out of streams, ponds etc), modern management systems are often quite different. Automatic waters may be massive time savers for people, but what do horses actually prefer? Many horseman may acknowledge that horses enjoy drinking from buckets far more than automatic waters. Indeed this has actually been borne out in the scientific literature. Given a choice, horses used buckets over automatic waterers almost exclusively. The type of waterer may also influence horse’s drinking behavior. In a study of horses never exposed to automatic waters, horses preferred float valve waters compared to push valves. Push valve waterers are those in which a horse must use some force of its muzzle against the valve. In fact, in that study, horses never consumed water from the push valves at all. It was believed the larger available reservoir of water in the float waterers encouraged the horses to drink more. In addition, push valves have a somewhat startling effect of the noise of water refilling the waterer. Horses were reluctant to return to the waterer after being startled.

Finally, the normal intake rate of water by a horse actually exceeds the flow rate of most waterers. Therefore a horse would need to drink much more often when using a low flow waterer. This may actually cause the horse to reduce its intake compared to being offered bucketed water. Now, this does not mean that automatic waters are out, but when selecting a waterer, look for one that maintains a larger reservoir of water or has larger surface area. Try to find a quiet waterer as well. Certainly horses can learn to use push valve waters, but during the training period careful observation should be employed to prevent dehydration. It may also be helpful to install a monitoring system in the pipeline feeding the waterer so that water consumption can be monitored.

Traveling with horses is also a key time to closely monitor water intake. Horses may reduce water intake for many reasons when being trailered for long distance. Stress, unfamiliar flavors of water, reduced feed intake and increased water losses may all create a state of dehydration in your horse. Often during travel, horses will reduce their feed intake, which subsequently reduces water intake. Remember that feed intake and water consumption are linked closely together. Reduction of water intake may lead to dehydration as horses typically increase water losses through sweating while trailering. Often we fail to consider how much muscular work a horse must perform to balance on long trips. Reduction of water availability may decrease your horse’s desire to eat as well. Thus, proper water and feed intake are a must for traveling horses. It is important that we try to break this cycle of reduced feed and water intake to ensure a healthy happy horse when it reaches its final destination.

Horses may also be reluctant to consume water which has an unfamiliar flavor. Addition of a flavoring agent may accustom a horse to a unique flavor which can mask new tastes. However, it is important to introduce the flavoring agent at a home. Horses accept a new flavors more readily when they are not stressed and are in their home environment. Use a training period prior to travel so that you do not discourage your horse from drinking. Also, in a test between apple and clover flavors, horses clearly preferred apple flavored water. There are multiple products available, so choose one that your horse likes.

Horses also drink when they eat, thus it is important to offer water simultaneously. Despite the fact that some horses may like to prefer dipping their hay in water, this is a normal behavior and need not be discouraged. While it may be messy, horses may due this to moisten their dry feed and make it easier to chew. In fact, in recent studies, horses consumed their hay much faster when it had been previously soaked. Presumably this was due to the ease of chewing of the soaked hay. This strategy may be helpful for horses which may have dental issues. Others have examined the particle length of forage fed to horses as a way to alter water intake. It has been suggested that chopping hay may encourage water intake or change water dynamics in the hindgut during long term exercise. However, water intake in Arabians fed either long stem hay or chopped hay did not differ, nor did the moisture percentage in the feces. Ultimately the total amount of forage consumed will directly influence water intake.

Horses are also sensitive to the temperature of their water. In horses completing work which created both dehydration and an elevation in temperature, horses initially preferred a saline solution that was 50 F compared to lukewarm or warm water. However, after about 20 minutes, the horses preferred the lukewarm water. Presumably the horses preferred the cooler water in order to help with thermoregulation. Season also affects water consumption. During cold weather horses reduce their water intake compared to more moderate temperatures. Therefore it is much easier for horses to become dehydrated in the winter, especially if their access to water is limited by ice formation. Horses actually prefer to drink water that is luke-warm compared to icy water. Clearly offering only icy water in winter can easily cause dehydration and potentially lead to colic. Therefore providing a tank or bucket heater in the winter is an important step in health management in the winter. Additionally, adding salt to the diet of the horse compared to offering only a free choice salt block may encourage water intake during cold temperatures. Other solutions to encourage water intake during cold weather include adding water to either pelleted feeds or creating bran mashes. In fact, in one study, horses fed a mash actually consumed more water voluntarily then horses fed a dry concentrate.

So, while you may lead the horse to water, and it may not drink; t it helps to have a source of water the horse actually prefers! Following these simple strategies can help ensure that your horse is always well hydrated.

Baby, It’s Cold Outside

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Written By: Walt Friedrich

It’s a beautiful time of year, Autumn, with trees decked out in full color, warm days, chilly nights, and our horses enjoying it as much as we do. We’re also keeping an eye on the calendar, because before long we’ve got winter on our hands, when all that brisk comfort has changed to cold and wind. We’re getting ready for it; laying in firewood, making sure windows and doors seal properly, shutting off outside water supply, shaking out winter clothing, “winterizing” the stable…and, of course, preparing our horses for the cold season.

For those of us in northern climes, it means the annual struggle with the question of whether or not to blanket. It’s odd, isn’t it, that we allow our horses to be just horses most of the time, but come cold weather, we feel the need to step in and overrule Mother Nature by blanketing them to make sure they can stay warm. Can’t blame us – we know the extent of discomfort that an icy cold wind brings in mid-January, and we bundle up for it bigtime, so let’s do the same for our beloved steeds. Right? Well, maybe — but let me take a moment to tell you a true story about Wally. It is pertinent.

Wally is not one to accept other people’s opinions without question. It has to make sense to Wally before he buys it, and he’s always researching one thing or another. And so he’s lived the skeptic’s life for some decades, making mostly good, well-thought-out decisions. Wally is also a horse-lover, and he keeps a few on his property. He calls them his “extended family”. Wally has always been strongly concerned over their welfare. Very early on in developing his horsekeeping methods, he agonized over whether or not to blanket, just as you and I have done. Blanketing seemed so logical because he knew well how the cold feels, and he wore a coat, so why shouldn’t his herd get the same protection? Yet highly respected horsepeople made strong arguments in favor of NOT blanketing – surely there must be something to it.

So one winter, Wally crossed his fingers and kept the horse blankets stowed away. Their coats had come in long and thick, and if it got “bad” enough, he could still break them out. Things went well; he noticed those thick coats seemed even thicker on particularly cold days, and when he investigated, he found that all those long hairs were actually standing on end, sticking straight up! And his fingers actually felt warm when he ran them through that bristling coat. Things looked promising, so he stuck at it.

And then one morning he woke to an outside temperature of -10 degrees F, quite cold for a northeast Pennsylvania winter morning. Wally headed to the stable, wondering if he had a herd of “horsickles” out there, waiting for some hay.

Well, he didn’t. His herd appeared to be enjoying the “delightful” weather, and that did it for Wally – he was convinced that his gang did quite well au naturel. And then the icing on the cake: the following morning it was almost -20 F – almost unheard of in these parts – and his horses were still totally unfazed. And so the heavy blankets remain folded and stored away, haven’t been used in years, and the horses continue to enjoy the cold winters as only horses can – bareback and outside 24/7.

What Wally discovered is the truth that it’s usually not the cold that’s their winter nemesis, it’s not even being wet – they love walking about looking like a snowman horse, and snow seems to actually help keep them warm. No, the problem is lack of shelter from the wind. Not all of us can prevent their being exposed to wind, but if we can’t, we must provide at least some respite. Anything will do – a stand of evergreens is ideal if there’s no stable or run-in shed available. We can even create a windbreak shelter by making a wall out of hay bales,  three or four bales high – they’ll have their shelter and eat it, too!

But let’s be fair about this subject: horses are individuals, even as you and I, and some may not take winter weather as well as most others.

Blanketing may be called for if your horse is shivering, or even just visibly uncomfortable in cold weather; older horses as well as ill horses and very young horses may appreciate a blanket despite their bodies’ natural coping abilities; if your horse is clipped, he has no protective coat, and can use all the help he can get; horses that don’t grow a sufficient winter coat are obvious candidates. Consider your options carefully, and remember that although you may need to override it, the best solution is usually the natural one.

If you believe blanketing is truly justified and not simply the result of “humanizing” your horse, do your homework. Blanketing is not a “one size fits all” situation, and there are many specific considerations you need to evaluate. There are countless websites on the Internet, providing information to help you decide, well worth your time and your horses’ comfort for you to study.

Beyond blanketing, there are other considerations to consider as winter approaches. For example, in winter horses do not need a cozy stall bedded with shavings –  it’s a lot of work and it won’t help; likewise, there’s no need to heat the barn – presumably inside the barn is already dry and reasonably windproof; they do not need extra grain – if you must increase their food intake, increase forage; and limiting movement is unwise – adequate movement is always best for horses no matter the conditions.

But what they do need is plenty of free choice grass hay, and adequate water (more on this in a moment). Be sure there is unlimited, free choice, loose, unrefined salt – preferably sea salt. And a horse that has trouble keeping weight on will need additional nutritional support, but not grain.

The other major cold-weather threat is colic. Colic refers specifically to nothing more than a pain in the belly. But the devil is in the actual cause of the pain: gas bloating sometimes hurts, but it usually makes a noisy departure leaving no tracks except for a trailing scent. An impaction, on the other hand, doesn’t go away without some help, like walking the horse for half an hour to stimulate fecal movement within the intestinal tract (terminated by, we hope, the deposit of a brown pile behind the horse). Sometimes an impaction needs still more help, commonly a vet will perform a procedure known as “tubing”, that will help clear the blockage. The most serious form of colic is hard clogging within the intestine that requires immediate surgery to correct. No matter the cause, if prompt action is not taken at the first indication of pain, the situation can develop into a serious condition.

Probably the primary cause of a winter colic attack has to do with water. As we head into the season, the horse’s digestive system continues to need a large volume of water, but his water intake drops along with the temperature, and the colder the water, the less he’ll drink. But he’s still got to digest his food and keep it moving down his intestinal tract, so lack of sufficient water can become a serious problem –potential intestinal upset and a colic attack. Complicating matters, with little or no water-rich grass to graze, only dry stubble, the need for water multiplies even further.

It seems as though the deck is stacked against him, and it is, but you can help prevent a colic attack  just by ensuring that his digestive system is functional and efficient. Here are the simple rules of prevention: first, use in-tank heaters to keep his water at a constant 50 degrees F; keep a reliable supply of hay (and grain, if you’re feeding it) to keep his diet constant; make no sudden changes in his diet; maintain his deworming schedule; use a prebiotic product to keep his intestinal gut garden healthy and thriving, providing consistently efficient digestion; feeding a simple mash every day is a great idea – just soaking hay cubes, or maybe beet pulp in water, adding an ounce of salt, can give him a couple extra gallons a day of water;

Finally, a few ideas and tips to make cold weather a little easier, especially on the senior citizens:

Spend a little quality time with him as often as you can. You are important to him — he knows you and he relies on you.

Get him a little regular exercise; longe or ride him for 30 minutes or so every week – it’s not much, but it will help keep his digestive system healthy, and in cold weather he’ll especially enjoy the activity.

Be patient with him; older horses especially may stress out in cold weather. New horses joining the herd, trailer rides, illness, vaccinations and deworming are all potential stressors. Avoid those that aren’t really needed.

Keep drinking water at a comfortable temperature.

Supplementing protein, calcium and phosphorus will help older horses through the cold season, as will a cup of oil per day for those hard keepers. Canola, flaxseed or rice bran oil would be good choices.

Don’t forget that daily ration of salt. Free choice loose salt is probably best, but a white salt block that’s always available is effective and easy to do.

Keep the farrier coming on schedule – their hooves keep growing regardless of the temperature.

Spraddle Leg

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Written By Lisa Steele, Fresh Eggs Daily

Hopefully you will never have to worry about a chick with spraddle leg ( also called splayed leg), but as is the case with everything else chicken-related, it’s always best to be prepared …just in case.

Spraddle Leg is a condition that a chick is either born with or develops within the first few hours of life whereby one or both legs slip out to the sides making them unable to stand or walk.

Spraddle leg can occur during incubation or the hatching process if the temperature is too high or varies too much during the incubation period or if the hatch is difficult for the chick. A less common cause can be a vitamin deficiency. The more common cause is an incubator or brooder floor that is too slippery for the chick to grip, which causes the legs to slide to one side. As a result the chick’s legs muscles don’t develop properly because of the lack of traction.

To try and prevent this condition, a sheet of paper towel or rubber shelf liner should always be put in the incubator just before the lockdown.

This will give the newly hatched chicks something to grip onto.

In the brooder box, newspaper should NEVER be used as the only floor covering.  Especially when it gets wet, it is too slippery and the main cause of spraddled leg.  Instead, I cover a few layers of newspaper with a sheet of shelf liner.  The rubber surface, just as in the incubator, provides a nice textured surface for little feet.

I change the newspapers and shelf liner out as needed, rinsing the shelf liner off and reusing it, and after a few days, add a layer of pine shavings on top.
Spraddle leg is easily correctable, but if not addressed quickly, the chick will not be able to get to feed and water and can die.

What you need to do is hobble the chick’s legs.  The easiest way is to cut a thin piece of vet wrap (approximately 1/4″ wide and 5″ long) and loosely wrap it around each leg, connecting the ends in the middle, about an inch apart, in sort of a figure eight.

The chick’s legs should be about normal width apart when extended. If the chick can’t stand up, you can make them a bit wider apart for better balance, but then bring them a bit closer together each day.
You can wrap some First Aid Tape around the middle to keep it secured.
Then be sure the chick has something it can easily walk on like paper towel, a bath towel or shelf liner.  At first the chick will have trouble standing up, but soon will be able to get around.  Ensure the chick has easy access to feed and water, but a shallow water dish with marbles or small stones in it is required so the chick doesn’t fall in and drown.  Also it’s best to keep the chick separate from other chicks at least until she learns to stand so she won’t be trampled.

At first it is helpful to support the chick and just let her try to stand and get used to having her legs underneath her.  Helping her get her balance will be beneficial and hasten her recovery.
Unwrap the legs and check the chick’s progress once or twice a day.  Leave the hobble on until the chick can stand and walk on its own. This could take from a few days to up to a week.  You should see results fairly quickly and soon your chick will be up and about.
Then make a solemn vow – no more chicks on newspaper!

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