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.

Vitamin E

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Written By Dr. Kris Hiney

We have already discussed two of the fat soluble vitamins in a horse’s diet. This month we continue with a closer look at vitamin E, a vitamin which is commonly supplemented to horses for a variety of reasons.  It is often used for aging horses, horses which have muscle disorders and horses which undergo strenuous exercise.  But how do you know if your own horse needs more vitamin E in its diet?

First, let’s explore the role of vitamin E in your horse’s body.  Vitamin E occurs in a variety of forms (both tocopherols and tocotrienols).  Of these, there are then four subgroups, α, γ, β and δ. While γ is the most common in the natural diet, the alpha form is the most potent in activity, the most supplemented and the subject of most studies.   In their natural diet, horses receive the most vitamin E as γ tocopherol from growing forages or harvested forage that was cut at an immature state.  As the plant ages, vitamin E decreases in content.  Vitamin E concentration also decays over time in harvested forages, as much as 50% over one month.  Therefore, older hays which have been stored for some time will have little activity.  If you also feed non-processed concentrates  to your horse (such as oats, barley, corn etc.) they will also be low in vitamin E. However, most commercial equine feeds will be supplemented vitamin E, usually as α tocopherol acetate.   It can be provided as either natural α tocopherol or synthetic, with natural forms having 36% more biological activity than synthetic.  The natural form has been shown to increase plasma α tocopherol concenrations greater than its synthetic counterpart but both are effective supplements.

(This is the structure of alpha tocopherol.)

Despite its form, vitamin E’s function is most frequently thought of as an anti-oxidant.  Vitamin E can work to eliminate free radicals which are formed through the incomplete oxidation of oxygen or other molecules.  During normal metabolism some amount of free radicals are always formed.  However, stress, work, aging, poor nutrition etc can increase the amount of free radicals in the body.  These are essentially molecules which are missing an electron, making  them highly reactive.   This is an unstable condition and the free radical can remove electrons from other cell components, such as lipids, cell membranes etc.  Vitamin E, along with other anti-oxidants donates an electron to the free radical, thus stabilizing it and preventing further damage.  One oxidized, vitamin E itself must be reduced back to its active form.  This is usually accomplished through the action of other anti-oxidants in the body such as ascorbic acid or glutathione peroxidase.  As the cells of the immune system have a high amount of polyunsaturated fatty acids which are quite susceptible to damage by free radicals, vitamin E plays a vital role in the optimization of the immune system.  Furthermore, vitamin E plays a role in reproduction, gene transcription and platelet aggregation.

(Traditional concentrates such as just corn and oats may be relatively low in vitamin E content.)

Currently, vitamin E is recommended to be fed to maintenance horses and breeding horses at 1 IU/kg of body weight (not sure if your horse is a maintenance horse, see Energy Requirements).  Growing horses  and lactating mares are suggested to need more vitamin E in their diet, at double the rate of maintenance horses or 2 IU/kg body weight.  Vitamin E intake for the working horse may need to be a bit higher.  While the current recommendation for working horses is 1.8 IU/kg body weight for moderate work and 2 IU per kg body weight for heavy work, many research studies have provided Vitamin E at higher levels.  Supplementation rates from 150-250 IU/kg DM, 300 IU /kg DM or even as high as 11.1 IU kg/body weight (in a simulated endurance race) have been found to be necessary to maintain blood and muscle concentration of vitamin E in more rigorously exercised horses.  To make these values seem more familiar, if we assume we are feeding a 500 kg horse 2% of its body weight, than the range of vitamin E would be between 1500 – 5500 IU of vitamin E per day in these studies.

Therefore, Vitamin E is often part of the suggested management protocols for horses which are heavily exercising or may have muscle disorders. In fact, in a study looking at endurance horses and supplementation of Vitamin E, the authors were unable to create a control group as no riders were willing to not supplement their horses!  However,i t has been difficult to prove the effectiveness of supplementation for the enhancement of the horse’s health.  In exercised horses receiving 300 IU/kg DM of vitamin E compared to 80 IU/kg DM, or no supplementation of vitamin E, the higher rate of supplementation did increase the muscle concentration of vitamin E.  However, it did not affect the indicators of oxidative stress in the muscle following a submaximal exercise test.  Perhaps a difference would have been observed with a more aggressive exercise regimen.  More recently, horses supplemented at a rate of 3000 IU per day of vitamin E compared to 80 IU/kg DM, underwent a training protocol.  The anti-oxidant capacity of all the horses increased following training, which is a natural adaptation to exercise.  There were no differences in reduced or oxidized glutathione peroxidase at rest, or total glutathione peroxidase.  However after a standard exercise test, the horses receiving 3000 IU vitamin E did have more reduced gluthathione peroxidase, suggesting a greater anti-oxidant capacity. Horses exercised to fatigue following 8 weeks of supplementation of 3000 IU of vitamin E had less muscle oxidation as measured by myofibril carbonylation( a measure of protein oxidation).

(Heavily exercised horses may need more vitamin E in their diet than maintenance horses or lightly worked horses.)
Determining if your horse has a vitamin E deficiency may not be as straight forward as taking a blood sample.  It has been shown that the concentration of vitamin E in the horse’s blood  varies irrespective of diet.  In one study, the variation within an individual horse in a 72 hr period would have shown the same horse as more than adequate in vitamin E, to marginal as well as deficient.  Therefore, it may be more important to look at your feeding regimen and the feedstuffs your horse consumes to determine whether or not they may have a deficiency.  The diet your horse is on may also affect his vitamin E needs.  Vitamin E is protective against the peroxidation of lipids in the body, especially the polyunsaturated fatty acids.  Horses which consume diets higher in PUFAs, which is certainly recommended in many cases, may increase the need for anti-oxidants in the body to prevent lipid perodixation.  Thankfully, many sources of PUFAs may be higher in vitamin E content.

If your horse is older, they may also be a candidate for vitamin E supplementation.  As horses’ age, their body systems may not function at the same level seen in their younger years.  As in people, the immune system of our aged horses may begin to fail.  When horses over 20 years of age were vaccinated for influenza, they were unable to mount the same immune response as their younger counterparts.  Therefore, older horses may be prime candidates for supplements which are known to complement the immune system.  In older horses fed vitamin E at 15 IU/kg of body weight, the bacterial killing ability of specific immune cells was increased, along with an increase in some, but not all, of the specific types of immunoglobins (or antibody).  However, in this study, the horses were previously on a marginally deficient amount of vitamin E. Therefore, it is not known whether it was the correction of the deficiency or the over supplementation that yielded positive effects.
Horses are fairly tolerant of relatively high amounts of vitamin E in the diet.  The upper range of vitamin E intake has been set at 1,000 IU/kg of DM. To think of this in more common terms, we will do a brief example using an 1100 lb horse that consumes 2% of its body weight.  Thus this horse would typically consume 22 lbs of feed per day.  We will convert this to kg to look at our total amount of vitamin E the horse should ever safely consume.  22 lbs of feed is equivalent to 10 kg of feed. Thus, the upper range of safe intake of vitamin E is 10,000 IU per day for a 500 kg horse.

However, vitamin E should not be used without caution.  In human medicine supplementation of vitamin E has not always yielded positive results, and if fact can actually enhance the disease state.  In humans undergoing heavy exercise, vitamin E supplementation actually decreased some of the positive adaptations to exercise.  In addition, heavy supplementation has been actually linked to mortality. As always, supplementation is never the answer for a properly balanced diet.   Overzealous  supplementation may actually work against your horse’s health!  But if your horse is older, more heavily worked or has added poly-unsaturated fatty acids in its diet, you might want to examine your diet for its Vitamin E content.

Next month we will finish our discussion of the fat soluble vitamins with vitamin K.

Obesity in Horses: II, Balancing Diet and Exercise

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Written By Dr. Kris Hiney

In Part I of this series, we talked not only about the difficulty in removing extra pounds from our equine companions, but also the health benefits that our horse will gain from doing so. Our strategies included seeking a more mature grass hay with a lower caloric density and reducing the amount of forage offered to the horse.   The horse will probably need to be confined to a dry lot, but fed in a way to minimize boredom related to reduced  feeding time. This month’s article will look more closely at the diet of our horse, to ensure that we are reducing the calories the horse receives, but are still feeding a balanced diet that provides sufficient amounts of our other nutrients.
We will continue to use the example of our 1300 lb horse who was at a body condition score of 8 and a goal weight of 1165 lbs. The maintenance requirement for the 1165 lb horse was 17.7 Mcal per day. We decided to feed the horse at a rate of 1.5% of its target weight in order to achieve the desired weight loss. That would mean our horse would consume 17.5 lbs of feed per day. Now, because we specifically chose a lower calorie hay which is more mature, it probably is lower in other nutrients as well. In order to ensure that your horse’s amino acids, vitamin and mineral needs are met, one should look for a low calorie supplement. Fortunately many reputable feed companies produce feeds that are designed for the easy keeper. Typically these feeds will be much higher in crude protein, minerals and vitamins and are designed so that you only need to feed one to two pounds per day. This ensures that your horse will not suffer from deficiencies while we achieve the desired weight loss.
Additionally, we can accelerate the horse’s weight loss by instituting a regular exercise program. Now, assuming our horse was at a body condition score of 8, it probably wasn’t on a consistent exercise program earlier. The key in implementing an appropriate exercise program is to realize that the horse is relatively unfit and we should begin exercise carefully. Ideally the horse should be ridden or worked five to six days per week.   If this is not possible, try to institute an exercise program at least every other day. Begin with intermittent periods of walking and trotting, and slowly increase the duration of the trotting periods. You should notice that the horse is able to recover its heart rate and respiration rate more quickly during the walking recovery periods as it becomes more fit. Then you can increase the intensity of its exercise program.
Now let’s take a look at how much exercise your horse needs for increased energy expenditure. For every 45 minutes the horse spends walking per day, it will expend an additional one Mcal/d of net energy.  But what exactly is net energy? To this point in time, we have always discussed the energy needs of the horse in terms of dietary energy or DE. Dietary energy refers to the energy available in the feed once the digestibility of the feed is taken into account. When we determine how much to feed our horse, it is always based on the DE concentration of the diet compared to the horse’s DE requirements. Net energy is more specific about the flow of energy through the horse’s body. Net energy refers to the amount of energy needed to support exercise, growth, lactation, etc. after other energy losses to the horse have been accounted for. These other energy losses include the energy lost from gas production, urine, the work of digestion and the heat lost from the digestion and fermentation of the feed. The energy that is left over after all of these losses is what is available for the animal to use for other purposes.
The efficiency of conversion of dietary energy to net energy of a horse in light-to-moderate exercise is only about 40%. Therefore, if the horse expends 1 Mcal of net energy, he actually used 2.5 Mcal of DE.  Even regular trail riding will greatly help the horse with our weight loss goals, but increasing the exercise intensity will increase the calorie expenditure even more. If we use the horse’s heart rate as a guide, we can determine how much exercise they need to perform to represent significant calorie expenditure. Let’s say we would like to increase our horse’s energy expenditure to 20% over his maintenance energy requirements. Our goal for our original horse, then, is to use an additional 3.5 Mcal every day.   Our horse’s typical heart rate when he is walking is usually around 60 bpm while trotting will elevate the horse’s heart rate to around 90 bpm. This relates to 24 kcal/min and 56 kcal/min of net energy respectively for walking and trotting.    If we convert that to Mcal of DE, our horse is consuming .06 Mcal /min or .14 Mcal of DE/min. To achieve an energy expenditure of 3.5 Mcal, that would mean we would walk our horse for almost an hour a day, or about a half hour of trotting.  However, these are heart rates of horses which already are fit. For the obese horses we are discussing, the heart rates are usually higher, thus less time will need to be devoted initially to exercising these guys. Good news for them! Heart rates for an unfit horse trotting have been recorded at 120 to 140 bpm! This would correspond to about 0.25 Mcal of DE per minute. Thus only about 15 minutes per day would achieve our increase in energy expenditure of 20%. Remember, this would be 15 minutes total of trotting with intervals of walking. As the horse begins to become more fit and its heart rate lowers, he will tolerate more exercise and will need to increase the amount of time he works to continue using the same amount of calories.
Alternatively, once our horse is fit, we can also add bouts of cantering or loping to his exercise program.   A horse which is cantering typically has a heart rate between 110 and 130 beats per minute and utilizes about .25 Mcal of DE/min. If we add 10-20 minutes of cantering to our exercise program, the duration the horse needs to be ridden to achieve our target energy expenditure would be about 45 minutes per day, which is probably more realistic for most horse owners. This would include a mix of walking, trotting and loping. Combining this regular exercise program with our restricted diet will help your horse add years to his life.
Good luck with your weight loss goals.