Omega Fields Presents Keys to Preventing Laminitis Article by Dr. Kris Hiney

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Newton, Wisconsin – Omega Fields’ Equine Nutrition Advisor, Kristina Hiney, Ph.D., has introduced a new article about key strategies in preventing laminitis in the equine. The article has been published in one of our Health E Letter issues, Omega Fields’ monthly, digital newsletter, and is also posted on their website, www.OmegaFields.com.

In the article, Dr. Hiney draws on her extensive personal knowledge, experience with equine nutrition and physiology, and scientific studies to try to identify which individuals may be at risk, and other strategies that may be employed to reduce your horse’s risk.

Dr. Hiney states, “While the outward appearance of your horse may give you an indication to whether they are susceptible to laminitis, there may be more to it than just which horses are overweight. There certainly appears to be a genetic link to laminitis.”

If owners wish to try and avoid the development of insulin resistance, the diet the horse receives may be critical. There is evidence that diets which avoid high amounts of sugars and starches, and have a low glycemic response, resulting in less insulin release. For horses which still need a significant amount of calories, diets which are fat and fiber based and properly formulated, rather than those which provide a higher glucose or insulinemic response, may prevent the development of insulin resistance. Certainly just monitoring body condition in the horse may be the easiest way to avoid insulin resistance. Although, if you ask any horse owner if that is easy you may get a different response! In addition, horses which receive regular exercise seem to be fairly protected against laminitis. However, it is difficult to know whether the exercise regimen aids in increasing insulin sensitivity, or is simply protective against obesity.

To read the complete laminitis article by Dr. Hiney that discusses the genetic role, obesity and insulin resistance, diet and lifestyle management, please visit our horse articles section on our website. <http://www.omegafields.com/blog/cat/articles-equine-articles/post/keys-to-preventing-laminitis/>

Dr. Hiney has been working with Omega Fields since 2008 to expand our connection with our customers, giving them the nutrition and health information from scientific perspective they would like to know. Each month, Kris presents a feature article concerning horse health in Dr. Kris’s Korner, her column in the Health-E-Letter. Click here to sign up for your free Health-E-Letter subscription delivered to your email address!

About Omega Fields
Omega Fields® is recognized as a minority-owned business. Its mission is to offer the finest quality, most nutritious products at fair prices, and to provide outstanding customer service. Omega Fields wants its customers to have exceptional experiences with their products, staff, websites and retailers.

Omega Fields is the first manufacturer in the animal health industry to use human-grade, non-GMO stabilized ground flaxseed, rich in fiber and antioxidants, and containing the optimum ratio of the full spectrum of Omega 3, 6, and 9 Fatty Acids for equine, goat, canine, poultry and human nutrition. The innovative use of flaxseed milled with a unique stabilization technology ensures long shelf life and superior quality for Omega Fields’ products.

For further information, contact Allison Kuhl, Omega Fields Director of Business Development at 920-550-4061, ext. 119; email Allison@omegafields.com; or visit www.OmegaFields.com or www.FLAX.com

 

Parasites: Anthelmintic Resistance

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Written By Dr. Kris Hiney

Last month we discussed management strategies that will aid in lowering the amount of internal parasites to which your horse is exposed. However, even with the best management practices available, it still may be necessary to employ chemical means to eliminate parasites. However, the use of anthelmintics (drug class which eliminates parasites) should not be done indiscriminately. A growing concern within the equine industry is the international development of anthelmintic resistance among the common parasites which infest horses. With no new drugs on the near horizon, we should take a hard look at their responsible use and our current management practices.
First of all, we should discuss how much of an issue parasite resistance might be, and what owners might have inadvertently done to help create it. It has been known for some time that ascarids and small strongyles have developed resistance to some drug classes, including benzimadazoles and the tetrahydropyrimidines or pyrantel salts, which include pyrantel pamoates and pyrantel tartrate. The other major drug classes of dewormers are the macrocyclic lactones or avermectins/milbemycins. Many horse owners would know these more commonly as the ivermectins or moxidectrin. These dewormers have been extremely popular to use because of the broader spectrum of parasites which they eliminate. Compared to benzimadozoles and tetrahydropyrimidines which kill large and small strongyles, ascarids and pinworms, the macrocyclic lactones also eliminate bots and stomach worms and moxidectrin eliminates several of the larval stages of small strongyles. Because of their broader range of efficacy, this has led many individuals to rely almost exclusively on these drugs in their management plan. However, there is a growing body of evidence that suggests that resistance issues to these drugs have begun to develop.
Ascarid resistance to ivermectin has been demonstrated in the Netherlands, Italy, Canada and Denmark. Furthermore, even within strongyles, the egg reappearance period, or the time between when no eggs are detected in the feces following deworming, to when they are seen again, has shortened from 9-10 weeks down to 5-6 weeks.  In Brazil, an increasing number of colic deaths in horses have been attributed to a growing resistance in the strongyles population.   In a recent issue of Veterinary Parisitology looking at anthelmintic resistance of horses in Finland, treatment of infected horses with ivermectin only resulted in a 52% decrease in the number of eggs found in the feces and 63% of horses had resistant parasites. Ivermectins were more effective against strongyles, but 44% of treated horses had parasites with demonstrated resistance. Comparatively, pyrantel treatment of horses infested with strongyles resulted in only a 43% reduction in fecal egg counts with 79% of horses showing resistance issues. To clarify, it is the parasite within the horse which harbors resistance, not the horse itself.
So why is resistance a growing issue? As discussed already, many individuals have relied exclusively on one type of dewormer. Eventually, as is typical in nature, organisms adapt to their environment to be more successful and to pass on their genetic code to future generations.    Essentially, once the worms adapt, or a few individuals survive a purge deworming, they are able to pass on these enhanced genetics to a future generation of worms which will also have that advantage of being immune to that drug.   If they are never exposed to a different type of dewormer, essentially the horse owner is just developing a breeding program for resistant worms! One strategy to adopt when thinking about “breeding” worms is to increase the number of refugia, or the population of worms which have not been exposed to dewormers. These would be the worms that would be in horses that were untreated, the encysted larval stages or perhaps those in the pasture. These non-exposed worms actually help to dilute out the population of resistant worms, and allow them to breed and pass on their more inferior genetics. To this end, many veterinarians now recommend that a fecal exam be performed on a horse prior to choosing to deworm. In this manner, horses which may not have worms present, are not unnecessarily dewormed. Also, a strategic deworming plan can be implemented, targeting only those horses with a significant worm burden. For example, a target concentration of 200 eggs per gram can be used.    Only horses which test to have a higher fecal egg count would be dewormed, while those horses with a relatively low burden would be left untreated, and thus increase the refugia.  This lowers our usage of anthelmintics and targets their use only at individuals which need it.
As horse owners, we may also be inadvertently contributing to resistance issues by using poor practices when we do choose to deworm our horses. Every time we under dose our horses with purge dewormers, we are creating greater tolerance in the worms. Many times owners actually under-estimate the true weight of their horse when deworming, or have a horse which spits out part of the oral dose. One easy tip for owners is to make sure there is no feed present in the oral cavity of the horse when deworming, the presence of which makes it easier to spit out the dewormer.
So what should a horse owner do? Certainly selecting only those horses which are known to be high shedders (or have a significant number of eggs present in their feces) would be ideal. However, there is very little incentive for the average horse owner to purse this type of program.   It is typically cheaper to just deworm the horse, rather than testing it first, and then follow up with deworming. More or less it becomes a personal choice of which practice to follow. If owners are unwilling to perform fecal exams, then it is imperative that they do rotate within classes of dewormers. Slow rotation strategies, which entail using a particular class of dewormer for one year, followed by a different class the following year, is an effective strategy.  Using a fast rotation program, or continually rotating between classes for every treatment is an alternative rotational strategy.   No definitive studies have been performed as of yet to suggest which strategy may be best for avoiding resistance issues. Additionally, the use of a macrocyclic lactone at least twice yearly is recommended, as these are the types of dewormers which can eliminate stomach bots. These are typically given after the first hard frost of the year, and prior to the spring thaw in the spring.
Ultimately, it is in our best interest as horse owners to employ strategic decisions about deworming our horses. A combination of management strategies and informed intelligent decisions about which horses to deworm and what products should be used. Ideally, a sound plan can be developed with your veterinarian or equine professional that serves the needs of your own horse, and the greater equine community as well.

Equine Parasite Management

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Written By Dr. Kris Hiney

Last month we introduced you to the major internal parasites which can plague your horse. This month we will discuss management strategies that you can use to decrease the parasite load on your horse, in part through an understanding of their life cycle. We can actually use the horse’s environment to help decrease our reliance on de-wormers and do our part to aid in the battle of anthelmintic resistance.
If you remember the life cycle of our most insidious parasite, the small strongyles, you know that the tiny infective larvae hatch from eggs outside of the horse. They then use the dew or moisture present on the grass to be able to wriggle around in the blades of grass and await your horse to come along and ingest them. Since they need this moisture as part of their life cycle and to be mobile, horses housed in stalls and dry lots are far less likely to be able to pick up infective larvae. It is pasture grazing, therefore, which is the key to the strongyles’ survival. Worm larvae will tend to be located in the thicker grass areas of the pasture and down in the thatch layer, where moisture remains longer.  The highest potential for infection will occur if your horse crops the grass close to the ground.
If you observe horses natural feeding patterns, horses tend to graze pastures into areas of roughs and lawns. The lawns, characterized by short grasses,  are the areas which are cropped closely to the ground and the roughs, which have longer grass, are the areas where horses choose to defecate and avoid grazing. Obviously the larger the area in which horses are kept, the less likely they are to graze near infective piles of horse manure. This will decrease their chances of picking up larvae. As stocking density of the pasture increases, or vegetative growth decreases, such as in times of draught, the horses will be forced to eat nearer these thick areas of grass just teeming with swarms of larvae. If the grass becomes too short, supplemental hay should be provided to avoid forcing the horse to graze in the roughs. Additionally, the pasture can be mowed to keep the roughs from spreading further into the pasture.
Many people employ dragging the pasture to break up manure piles and spread them through the pasture to prevent the formation of roughs. However, if you use this strategy, you must understand that you are effectively dispersing the eggs and larvae far more thoroughly than they could ever do themselves. Even on their own, larvae can spread 4 to 12 inches from their original pile, and even further if aided by heavy rainfall. Therefore, if you drag the pasture, keep the horses off the pasture for at least two weeks. Preferably the dragging should be done in the hottest part of the year in order to expose the larvae to heat and dehydration. Cool temperatures allow the larvae to survive longer, so it is not advised to drag during the spring and fall.  If you must drag in cooler weather prevent the horses from grazing for an even longer period of time. As strongyles larvae are especially hardy and can survive winter quite easily, this is really not a good strategy for trying to kill the larvae.  Finally, if you are going to spread manure on pastures as a means of disposal, never spread fresh manure. Make sure it has been thoroughly composted before applying it to your pasture.
In an ideal world, pasture rotation allows the best management strategy to reduce strongyles infestation  in your horses. Horses grazing in fresh new pasture will avoid grazing near manure piles, and have a lower chance of re-infesting themselves. Letting pastures lie dormant will also allow any eggs or larvae present to die before horses are introduced. If space and equipment allows, putting pastures into hay production will allow parasites to die as well. Finally, if you own multiple species of animals, grazing pastures alternatively between cattle, goats and sheep will reduce your parasite burden, as the worms are host specific. Obviously all of these strategies do require a significant amount of acreage and fencing to be effective and may not work for everyone.
Remember, for strongyles elimination, heat is your friend. Only drag pastures during the hottest part of the year, and do not allow horses back onto the pasture for at least two weeks. Use separate pastures for winter pasture and summer pasture. Remember, winter does not kill the parasites. In cooler climates, parasites will not die after emerging from their dormant state until about June, May in hotter climates. If you do have a clean pasture, before you turn horses onto it, chemical deworming can prevent parasite infestation. Horses that are dewormed should be held on dry lots for several days before turning them out. This will allow all the eggs that the mature female has deposited to pass through your horse’s digestive tract. When your horses enter their new pasture, they won’t be bringing any “friends” with them!
What about the other parasites in your horses life other than strongyles? There are certainly management strategies which will help control their populations as well. For ascarid control, remember that these worms are primarily a problem for young horses. If possible and space allows, rotate which pastures house young horses with adult horses. However, even this may not be completely effective as ascarids can remain alive in the environment for several years. Essentially, if foals and young horses have been housed in a pasture, it is fairly likely that ascarids are present. Unfortunately, as ascarids don’t involve the same strategy for survival as strongyles, they can also infest the young horse in stalls and dry lots. This is typically why young horses are dewormed more frequently than older horses.
Stomach bot larvae and adult fly control are unfortunately only going to be controlled through the use of anthelmentics. The adult form can fly for miles so even if you have a great deworming program, if your neighbors do not, their flies will simply fly over to your property to lay eggs on your horse.
Tapeworms are relative newcomers when discussing parasites in horses. While not new to the horse, they are new to us, so not as much is known about them. They are believed to have a similar susceptibility to climate as the small strongyles, but may be hardier. More horses in northern climates have been exposed to tapeworms, which would indicate that these parasites are relatively cold resistant, but may have a susceptibility to heat. Therefore, follow similar management protocols as you do for small strongyles control.
From looking at the parasites life cycle and their means of infesting horses, it is clear that horses are often dewormed more frequently than is really necessary. As anthelmintic resistance becomes a growing issue in horses, we need to understand the ways in which we can manage horses to reduce their parasite burden. Next month we will tackle the issue of anthelmintic resistance and discuss which deworming strategies might be the most correct option for your horse.

Parasites: Who are you really feeding?

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Written by Dr. Kris Hiney

This month we will discuss other aspects of horse management that directly affect the nutritional status of your horse. While most horse owners are familiar with deworming their horses regularly, current recommendations from many equine practitioners are to be much more strategic with our deworming. There is a growing concern that parasite populations are developing resistance to almost all types of anthelmentics (drugs used to eliminate internal parasites). As no new anthelmentics will soon be offered to the public, this could represent a real risk to the health of our horses. In order to understand these issues, we will begin with a review of the major parasite classes in horses.
While there are many types of worms which infest horses, we will address the major classes that represent the most health risk to your horse; ascarids, strongyles, tapeworms, bots and pinworms. Ascarids, or Parascaris equorum, are a type of round worm which grow to a substantial size of 8-15 inches within the intestine. They are yellowish in color and may be occasionally seen in the feces. Despite their robust size, much of the damage created by these parasites involves their life cycle and migratory journey through the horse. Adult females pass eggs into the horse’s feces, where they spend 1-2 weeks in the environment before they are capable of infecting a new host. Horses ingest the infective eggs by grazing or eating in contaminated areas. Once inside, the larvae burrow through the intestinal lining and enter the bloodstream, where they travel to the liver. They then travel to the heart and then the lungs. Ultimately they enter the alveoli of the lungs where the horse coughs them into the oral cavity and then are swallowed back down into the stomach and intestines. The entire life cycle of the ascarid takes about three months and the journey these parasites take can cause significant damage and scarring of the tissues. A heavy parasite load of adult worms can even lead to blockage of intestines.   Young horses are the most susceptible group of horses to acquire ascarids, as well as weak, or malnourished horses. Coughing and nasal discharge in young horses may actually be a sign of ascarid infection. Older horses eventually develop an immunity to these parasites, so ascarids are primarily an issue with horses under two years of age.
Strongyles exist as both large and small strongyles, with many sub-species. The three main species of the large strongyles are Strongylus vulgaris, Strongylus edentus, and Strongylus equinus. Small strongyles actually have about 50 different species. Strongyles are also the most damaging of the parasites that horses will encounter. Similar to the ascarid, the females lay eggs which are shed in the feces. Unlike ascarids, they hatch into infective larvae that the horse ingests. The larvae molts three times before it is ready to infect the horse. The larvae actually crawl up the blades of grass in the dew. The larvae can crawl up or down multiple times waiting for a host, or even burrow into the ground when the weather isn’t favorable. Unfortunately for the horse owner, these parasites are extremely hardy and can persist through the winter.
The characteristics of the large and small strogyles life cycle make them particularly damaging. Large stronglye’s life cycle involves two stages where they migrate through the arterioles and arteries which supply blood to the intestine. Unfortunately, wherever these larvae burrow through the intestinal wall to migrate, all of them will return to one single location, the cranial mesenteric artery. Here they congregate and can cause immense damage. They can cause hemorrhaging, blood clots, or even rupture. The blood clots themselves can break free and travel further down through the blood supply to where they block blood flow and create a thromboembolic colic and even death. Oddly, enough lameness can also result from blood clots traveling to the legs as well.
Small strongyles have an additional strategy to help them survive. As they pass through the horse’s intestinal wall, the horse’s immune system is also trying to wage war against the larvae. However, the larvae are too big and travel too fast to be eliminated. The final migration of the larvae and complete maturation is actually held in check by the presence of adult strongyles in the lumen of the intestine. Essentially the adults provide feedback to the larvae that there is no room at the inn. When the larvae get that message and slow their migration, they become encysted within the intestinal wall by the immune cells. Here they can lie in wait for several years to take their turn at being the adult worms in the intestine. The horrifying reality is that when the adults die of either natural causes or by our purge deworming of the horse, the encysted larvae “wake up” and emerge to replace the newly vacated intestine. Within 6-8 weeks they will have matured and begin laying their own eggs to begin the cycle anew. Again, it is the pattern of traveling through the tissue that can cause a great deal of damage to the horse.
Relative to those bad boys, the rest of the worms which typically invade horses are mild in nature. The other major parasite classes which trouble horse owners are pinworms, stomach bots and tapeworms. Pinworms have a very simple life style compared to ascarids and strongyles. Adult females have a rather interesting feature, however. Not content to just shed her eggs into the feces, she actually deposits the eggs on the horse’s anus. This causes irritation to the horse who then scratches on anything available in the environment, effectively dispersing them. The horse then incidentally ingests the eggs, which hatch in the intestine where the larvae mature. Thankfully, these worms do little damage to the horse because their life cycle does not involve migrating through sensitive tissues. However, they can cause great irritation to the horse and robust itching of the tail head.
Tapeworms in horses can also cause reduced nutrition and potential blockages due to the preferred location in the horse’s gastrointestinal tract. The main species of tapeworm which inhabits the horse fixes at the ileocecal junction, or where the terminus of the small intestine joins into the cecum. A heavy parasite load can result in blockages, thickening of the ileocecal valve or even intusussecption, when the intestine rolls over itself due to regular peristaltic action. The tapeworm also has a separate host for part of its life cycle. While the adult parasite resides in the horse, the eggs of the tapeworm are actually ingested by a type of mite, which the horse then later ingests while grazing. There does not appear to be any age related immunity to tapeworms, as they are found in all ages of horses.
Finally, stomach bots are frequently seen in horses as well. The stomach bot, or Gasterophilus, also has subspecies, which include the horse bot fly, the throat latch bot, and the nose bot fly. The adult fly form can actually fly for several miles in search of a suitable subject on which to lay its eggs. The female hovers near the horse and deposits single eggs on one hair at a time. The eggs actually hatch into larvae within 7-10 days of being deposited. They then wait to emerge until the horse licks or scratches at the eggs. The larvae then enter the mouth and bury themselves in the gums, tongue or lining of the mouth where they hang out for a month. As they mature to later stages of larvae, they move into the stomach where they attach to the non-glandular or upper part of the stomach. The larvae live in the horse’s stomach for 9-12 months, before they and pass out into the feces. This typically occurs in late winter to early spring. There the larvae pupate and remain in the feces for several months. The flies then emerge in late summer or early fall, find mates and renew their life cycle. The damage the bots cause to the horse can occur in the mouth where they cause great irritation and even form pus pockets or cause the teeth to loosen. Large numbers of larvae in the stomach can cause blockages and erosion of the stomach lining. They, like all internal parasites, can result in reduced nutrition being delivered to the horse. An important heads up to horsemen:  when handling horses with bot fly eggs on their hair, use caution. While rare, the larvae are capable of burrowing into human skin, and if one rubs their eye after handling bot eggs, they larvae can actually invade the eye. I’m quite sure the last thing anyone wants is a bot larvae living in your eye!
Next month we will use what we know about these parasites to develop management strategies to reduce their ability to infect our horses. After that, we will discuss strategic methods in using anthelmentics in order to reduce our reliance on medications and reduce the spread of resistance in parasites which invade our horses.

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.

Obesity in Horses

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Written By Dr. Kris Hiney

Just like in people, many horses suffer from obesity related health issues. Overweight horses can have more trouble with joint issues, suffer from exercise intolerance and can even develop metabolic problems. While many horse owners know the risks of having an overweight horse, it may be difficult to reduce weight in these horses – certainly the horse is usually an unwilling participant!  In this article we will address management techniques and dietary strategies designed to reduce weight, but still keep the horse physically and mentally healthy.
First of all, which horses are good candidates for losing weight? Ideally most performance horses should have a body condition score around five. Horses that are slightly overweight, or have a body condition score of 6 or 7, shouldn’t be at a great risk for health issues, but certainly will perform better at a condition score of 5 or 5 1/2. Horses above a 7 have more risk of developing health issues such as insulin resistance, metabolic syndrome, or even Cushings in their later years. If the horse with a high body condition score also has uneven fat distribution, he is more likely to have metabolic issues, and may even be harder to remove weight from than a horse with a more even fat distribution (personal observation). Horses that have cresty necks, substantial amounts of fat over the tailhead, enlarged abdomens and fat in the area of their mammary glands or sheath fit this category.   It is more critical for these individuals to lose weight. Now that we have identified the horses which need to lose weight, let’s address a healthy weight loss plan.
One of the first issues to address is the quality of the horse’s forage. Ideally we will feed dieting horses harvested forage/hay, rather than pasture as it is easier to monitor their intake. Horses that are overweight will do better on mature grass hay which has less caloric density than alfalfa or alfalfa-grass mix. When selecting hay, look for more mature hays that have been cut at a later stage of growth. Typically these will be coarser stems and have seed heads present in the hay. However, when looking for lower energy hays, don’t sacrifice the overall quality of the hay – it should not contain weeds, debris, dust, mold, etc. We are just looking for fewer calories, not hay that your horse shouldn’t eat! Once we have the correct hay type, the owner will have to limit their horse’s intake. This can often be confusing, as we typically teach owners to feed based on a percentage of the horse’s body weight. However, in this case, we have a horse that weighs too much, and is consuming more hay/forage than it should. Let’s take a look at the math involved to determine how much the horse should eat.
For an example, we will start with a 1300 lb horse who has a body condition score of 8. If we looked up this horse’s energy requirements for maintenance, it would need 19.7 Mcals per day. But that energy requirement is based on a horse that is in a lean body condition. Remember that it takes more calories to maintain metabolically active tissue like muscle than it does fat.   So even if we fed our horse at its maintenance requirement, it is still receiving too much energy for its body type. We will now assume that for every body condition score we want the horse to lose, it should lose about 45 lbs. For our 1300 lb horse, our target weight is actually closer to 1165 lbs [1300 lbs-(45lbs x 3 body condition units)]. The maintenance requirement for the lean 1165 lb horse is 17.7 Mcal per day.    Using these numbers, we will calculate out how much hay this horse would need to provide that amount of energy. For this example, I will use a grass hay of advanced maturity with a caloric density of .86 Mcal/lb as fed. The amount of hay the horse would consume using our 19.7 Mcal figure would be 23 lbs of hay (19.7 Mcal/0.86 Mcal/lb), while the horse would receive 20.6 lbs of hay if we intend to provide 17.7 Mcal (17.7 Mcal/ 0.86 Mcal/lb). Let’s compare that with the standard feeding guidelines for horses based on body weight. If the target weight of our horse is 1165 lbs, and we fed at 2% of the target body weight, our horse would receive 23 lbs of hay. That certainly wouldn’t work because that would provide enough calories to maintain his current weight of 1300 lbs! So how much do we need to reduce his hay intake? If we feed the horse at 1.75% of its target body weight, the horse would receive 20.4 lbs of hay per day. However, even feeding at this rate will probably not get us to their target weight. Therefore, in order to really achieve weight loss in our horse, we should probably feed closer to 1.5 % of the horse’s target weight. That means our horse would only be eating 17.5 lbs of hay per day. For the horse owner, this means that in order to successfully achieve weight loss, we need to get a scale out to the barn, and physically weigh out the amount of hay the horse will consume in one day. While this may be time consuming, it is the most accurate technique to deliver the correct and consistent amount of calories.
Now let’s talk about some other practical issues. A horse that is only consuming 1.5% of its target body weight is going to have some “free time” that it is not used to having. We need to provide mental stimulation for this horse or it may development unwanted stereotypies such as cribbing or wood chewing. Continual stalling would not be ideal as this will certainly lead to a great deal of boredom and frustration. If possible, the horse should be kept in a dry lot (free access to pasture certainly won’t help!) with secure fencing. Do not underestimate the horse’s ability to get through the fence to graze! Also, providing other horses with which to interact, stable toys, etc. will help relieve boredom. If you find your horse finishing his meals too quickly, putting the hay in a hay net which is tightly woven may also slow down his rate of intake and alleviate boredom. While these strategies may sound tedious, it is important in order to improve the overall health of your horse.
Next month we will continue to discuss the dietary needs of a horse in a weight loss program, as well as how to safely use an exercise program to encourage weight loss.

Feeding Horses for the Prevention and Management of Laminitis

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Written By Dr. Kris Hiney

Nothing is more devastating to the horse owner than to have a treasured partner be afflicted by the painful, crippling disease of laminitis. Laminitis can be a debilitating disease that may ultimately result in the death of the horse or humane euthanization. Unfortunately there are so many factors that can manifest in development of this syndrome that it can be difficult to sort through.
To understand the development of laminitis one should really understand the physiology of the equine foot. Essentially the hard keratinized tissue which forms the hoof wall is held to the soft tissue by the interdigitation between the sensitive and insensitive laminae. The insensitive laminae (seen here in Figure 1) is formed in vertical sheets on the inside of the hoof wall. 
Figure 1. An interior view of a horse’s hoof with the soft tissues removed. 1b. A schematic of the vertical lines of insensitive laminae lining the interior of the horse’s foot.
Connecting to the insensitive laminae is the sensitive laminae, which is living tissue requiring an adequate blood supply of oxygen and nutrients to survive. When an alteration of blood flow or a vascular insult occurs inflammation or even death of the sensitive laminae can occur. The sensitive laminae ultimately stabilize the internal structures of the horse’s hoof, including the third phalanx (or coffin bone). When this stable connection is lost, the pull of the deep digital flexor tendon on the base of PIII rotates it out of place. This condition is referred to as chronic laminitis or founder.
Figure 2. The sensitive laminae which connect the hoof wall to the horse’s foot.

Figure 3. A foundered hoof where PIII has rotated out of place due to the pull of the deep digital flexor tendon.
 
There are many reasons why blood flow can be disrupted to the equine digit. Laminits is often a systemic disease which is only visualized in the foot. While digestive issues lead the list of causes of laminitis there are other physical insults which can occur as well. When procuring wood shavings from a reputable dealer, care should be taken never to include those of the black walnut tree. These shavings contain the chemical juglone, actually a toxin which can kill other plants in the black walnut environment. Other physical causes are concussive trauma, from being ridden on hard surfaces resulting in decreased blood flow to the foot, and excessive loading (i.e., one limb is severely lame resulting in extra loading to the sound limb). Endotoxemia, such as what might be seen in a mare with a retained placenta, may also result in the development of laminitis.
 Nutritionally, a whole series of gastric insults can alter blood flow to the foot.  These include a carbohydrate overload (the classic example of the horse breaking into the feed bin) which leads to an alteration of fermentation in the hindgut.  In order to prevent starch from escaping enzymatic digestion in the small intestine and escaping to the hind gut, it is recommended to avoid a starch intake of more than 2-4 g/kg of body weight per meal. Therefore, a 500 kg horse should receive no more than 1-2 kg of starch per meal.  Pasture grasses have also long been known to precipitate bouts of founder, but typically only in susceptible populations. Ponies, and horses with thrifty genotypes are the most likely to suffer from pasture-associated laminitis. It is believed to be caused by a high level of fructans, although the quantity of fructans required to cause laminitis is unknown. Fructan content is known to vary with the time of year, with a higher content seen in the spring, when most pasture-associated laminitis occurs. Horses which are susceptible to pasture-associated laminitis should also limit their intake of pasture grass in the afternoon, when photosynthesis throughout the day has resulted in a higher level of fructans in the plant. The levels of water soluble carbohydrate gradually decline through the night, making grazing in the morning relatively safer. As the majority of horses which develop laminitis due so on pasture, rather than through the owner feeding excessive concentrates, at least some thought or caution should be used when grazing horses. Ideally horses should be introduced gradually to consuming fresh grass, and susceptible horses’ grazing should be limited to when fructan concentrations are at their minimum.
If a horse does develop chronic laminitis, unfortunately there is little the owner may do nutritionally to manage the horse. Obviously exposure to pasture grasses at peak times of fructan concentration should be avoided. Also, the horse should be managed to lower body weight to decrease the mechanical load on the laminae. Low energy forage should be the primary feed for the foundered horse. However, because low energy forages will typically be deficient in protein, minerals and vitamins, it is important to ensure that the horse is supplemented with a low energy concentrate to make up for dietary insufficiencies. As these horses are often in a great deal of pain, NSAID administration may often be needed, but can also contribute to gastrointestinal upsets. Alternatives to NSAIDS, such as Omega-3 fatty acid supplementation, may help to alleviate some discomfort, without the negative side effects.
Overall, close attention to the diet of the horse, avoiding GI disturbances or causing fluctuations within the hind gut, and limiting grass intake during periods of time where fructan concentrations can be high, will hopefully prevent the horse from ever experiencing this deadly disease.

Feeding Horses with Respiratory Allergies

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Written By Dr. Kris Hiney

Similar to people, horses can develop allergies to environmental contaminants that lead to asthma-like symptoms. In the equine world, this syndrome is referred to as recurrent airway obstruction (RAO). It was previously referred to as chronic obstructive pulmonary disease or (COPD) but due to dissimilarities with the syndrome observed in humans, RAO is now the preferred term. When some horses are exposed to dusts and molds, they develop allergies.  Why some horses do and others do not develop allergies is unknown. There is some evidence that this disease may be genetic. Horses born to affected parents are three times more likely to develop RAO than horses born to non-affected parents. Therefore, if you know your horse is predisposed to RAO, it is even more important to identify the symptoms and to properly manage its environment.
Identifying RAO
When the horse is exposed to an allergen, the body responds by increasing inflammation through the bronchioles coupled with bronchoconstriction.  The lungs increase in mucus production which the horse may not be able to clear easily. Frequently nasal discharge is seen, along with coughing, an increase in lung sounds and more distress during breathing. Lung sounds are typically heard with expiration, or the horse will “wheeze” when breathing out. Continual exposure to allergens may lead to fibrotic changes within the lungs. This will result in a horse which cannot take in oxygen to the same extent as an unaffected horse. You may notice that the horse has an increase in respiration rate over what is normally experienced during exercise, or he may become more exercise intolerant or fatigue easier. Horses with this syndrome which have had it more severely or more chronically may even develop a “heave line”. This is due to the hypertrophy of the abdominal muscles which must be used to assist the animal in breathing, rather than just solely using their diaphragm.
Management of the RAO horse 
As pollen and mold counts increase in the environment, horses with RAO will experience more symptoms or episodes of RAO. Often barns and stables are not designed with proper ventilation in mind. This contributes to a continual exposure of the horse’s respiratory system to particulate matter. Hay and straw bedding ideally should always be stored in a separate building from where horses are housed, and certainly not overhead. Additionally, the stalling area should be separate from the riding arena. All the dust that is kicked up while horses are exercising can greatly exacerbate the problem. Ever think about how much dust is stirred up into the air while the barn aisles are being swept? Ideally all of this dust exposure should be minimized and RAO affected horses removed from the barn whenever dust is stirred up. One of the best changes to management practices of the RAO horse is simply to house them outdoors. Often an improvement in airway function is seen within days.
While horses stabled inside are clearly more likely to be exposed to particulate matter, horses on pasture during the summer can also have trouble. This even has its own nomenclature,  summer pasture associated obstructive pulmonary disease or SPAOPD. Horses with this syndrome should be kept off pasture during the summer months, but can be housed outdoors during the rest of the year. If horses must be housed inside, whether they are SPAOPD or perhaps competitive horses that must be stalled, it is imperative that the environment is as dust free as possible. Straw bedding may not be a great choice for RAO horses but shavings can also contain molds similar to those in hay and straw. High quality straw may actually be lower in spore count that some shavings. Alternative beddings may yield the best results such as cardboard or newspaper pellets. If straw or shavings are used, remove any RAO affected horses while bedding is introduced into the stalling area. Essentially, let the dust settle before the horse is put back into the stall!
Feeding management
Ideally the RAO horse should graze fresh pastures as much as possible, but obviously this is not always possible.  One of the most immediate dietary changes for the affected horse is to absolutely eliminate any moldy hay or straw that may be in the horse’s environment. While moldy hay should never be fed to horses, it is more critical with RAO horses.   One of the difficulties in finding suitable hays for RAO horses is that humans may not always be able to detect the presence of mold if it is not obvious. Try to find hay sources from a knowledgeable producer who bales high quality hay. The type of fungus which produces the most damaging fungal spores prefers relatively hot temperatures. This would be seen in poorly cured hay, or hay that is baled at too high of a moisture content. The heating which occurs during spoilage is a haven for these fungi.  Round bales may not be an ideal choice, unless they are stored completely inside and are never subject to any sort of spoilage. Additionally, round bales encourage the horse to almost bury their head within the bale, making the immediate breathing area of the horse very dusty. Completely pelleted diets might be a good choice for these horses at it greatly eliminates the dust exposure to the horse while feeding. The quality of the pellet is also critical. Uncoated pellets may break down more easily and have a substantial dust component. Hay cubes and haylage are also alternative feeding strategies.   Moistening the feed can also help in dust suppression prior to feeding. Hay only needs to be soaked for 30 minutes to achieve optimal dust suppression. Beyond that time no additional benefits are seen. However, the down side to soaking the hay is that some of the nutrients are leached out into the water, including P, K, Mg and Cu.
Beyond eliminating dust and molds other dietary therapy may be aid the RAO horse. Supplementing RAO horses with additional anti-oxidants in the diet may be helpful. There is an increase in free radical formation or reactive oxygen species (ROS) in horses with lung inflammation. In fact, the increase in RAO may increase the upregulation of genes which produce inflammatory factors such as interleukins. Horses with RAO given a supplement of vitamin C and E plus Se resulted in less airway inflammation and an increase in exercise tolerance. Other natural sources of anti-oxidants such as sorghum and omega 3 fatty acids have not yet been studied for their effectiveness in RAO horses.   Additionally, due to the increased energy requirement just to breath, RAO horses are often underweight. The sustained stress to the horse’s system may also contribute to this weight loss. You may need to find a feed with an increase in energy density, such as a fat added feed to help maintain its body weight as well as additional anti-oxidants.
If one follows these management guidelines carefully, RAO horses may be symptom free for years to come.   While pasture is ideal for RAO horses, performance horses which need to be stalled can be kept healthy with a rigorous adherence to maintaining a dust and mold free environment and proper dietary management.

Preparing for the Breeding Season

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Written By Dr. Kris Hiney
While breeding season may be the last thing on anyone’s mind at this time of year, it will be coming soon. Now is the time to ensure that your mare or stallion is going to be at their optimal reproductive efficiency. While much of a mare’s or stallion’s fertility depends on other factors such as age, condition of reproductive organs, etc., there are some basic management steps we can take to ensure that as few cycles of inseminations are needed to get a mare pregnant. Multiple breeding attempts can quickly outstrip the original stallion breeding fee and be a significant cost to the mare owner. Often we forget that every shipment of semen may be an additional cost, followed by extra veterinary fees, mare board, etc. Therefore it is in the mare owner’s best interest to have her in optimal condition before the first breeding attempt ever occurs.
So how do you prepare your mare and stallion in January to begin breeding anywhere from February to mid-summer? The easiest place to begin is to look at your horse’s body condition score. For a mare, we want her to be at a body condition score of at least 5 or 6 (see “Too Fat, Too Thin, or Just Right”). A mare in this condition would be a moderately fleshy mare whose ribs are covered by fat, has evidence of fat deposition behind her shoulder and over her tailhead, and whose back is level. Mares that are a higher condition score than that may still have no problem getting pregnant, but are unnecessarily obese. This may result in more wear and tear on her joints. Additionally, as there is no increase in reproductive efficiency, maintaining a mare in too high of condition may just be a waste of feed costs. Furthermore, if she has chronically been obese with localized fat deposition, she may even be at risk for metabolic syndrome or insulin resistance (see Equine Carbohydrate Disorders, Part 3: Metabolic Syndrome).  If your mare is diagnosed with metabolic syndrome, it is important to correct her metabolic profile and manage her carefully through the breeding season. Altered hormonal profile can impair her ability to become pregnant and certainly extra weight in a laminitic mare may increase her level of pain.
If we look at the opposite condition and the mare is too thin, she will need more cycles to settle compared to a mare at adequate condition. She also may take longer to return to normal cyclic activity following winter anestrous (when mares cease to cycle due to the shorter day length). Thin mares’ conception rates may be lower, and if she foals in a thin condition, she may take longer to begin cycling again. With so many negative effects of trying to breed a thin mare, one of the easiest ways to increase reproductive efficiency is to put weight on your mare!
Stallions also use more energy in the breeding season due to the increase in their activity levels. Stallions which breed mares in an intensive live cover breeding system will of course need more energy than a stallion which is bred only once every other day. Stallions which are more extensively used would have energy requirements similar to a light to moderately exercising horse, and their maintenance requirements will also be elevated (see “Energy for Work”).  Typically, stallions are simply more active during the breeding season as they exhibit their normal sexual behavior. Ideally, stallions should be maintained in a body condition score close to 5 throughout the breeding season.
Beyond just meeting a stallion’s energy requirements, feeding of Omega-3 fatty acids may help improve his reproductive efficiency. In a study by Harris, et al, published in 2005 in Animal Reproduction Science, stallions supplemented with dietary Omega-3 fatty acids increased their daily sperm output.  Furthermore, there was an increase in morphologically normal sperm in the supplemented group.  The greatest response was seen in the stallion with initially the most morphologically abnormal sperm. In this study, one stallion who was considered to be a “poor cooler” improved his post cooling progressive motility from 23 to 38% in a 48 hour test cool. Therefore, supplementation of Omega-3 fatty acids may be a valuable tool in improving the reproductive characteristics of sub-fertile stallions.
Basic guidelines for increasing body weight and condition in horses are really no different for the broodmare or stallion than in other classes of horses. The quicker the gain is needed in the horse, the larger the increase in calories which must be offered daily. If you only have two months to get your mare in condition, you need to increase her energy intake by 30-40% to increase her body condition score by one number. If we have three months, which may be more realistic, the energy requirements increase by 20-30%. Remember, however, if you are trying to accomplish weight gain during the winter, she may also have an increase in energy requirements due to her need to thermoregulate. This will make weight gain more difficult. To add calories quickly to the diet, look for a fat-added feed that will be digested quickly and efficiently.  Remember that fat offers 2.25 x the calories that will be in grains which consist primarily of simple carbohydrates. Fat will also disrupt the metabolic profile of the horse to a lesser extent than a diet high in sugars and starches.
Of course, beyond caloric intake, always ensure that your breeding horses are consuming a complete balanced diet in respect to all nutrients, have good health care and are suitable candidates for breeding. Breeding horses is a big responsibility in terms of the care and well-being of the mare, stallion and the subsequent offspring.

Equine Carbohydrate Disorders Part 3: Metabolic Syndrome

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Written By Kris Hiney
Imagine a bright spring day. You excitedly turn your horse out to indulge in the fresh spring grass as a special treat. You return in a few hours to collect your companion, but instead are met by an unhappy painful horse, slowly limping its way back to the gate.
Sound familiar? Unfortunately for some owners, this is an all too real scenario. Many horses suffer from carbohydrate sensitivities, or metabolic syndrome, which make them extremely susceptible to changes in carbohydrates in the diet.  One may also hear these horses referred to as insulin resistant, almost like Type II diabetes in humans.  In recent years there has been an upsurge in the number of studies and articles written about metabolic syndrome in horses. While awareness in the general public has increased, many horsemen still wonder if their horse is, indeed, one of these individuals. Should they be paying strict attention to every type of carbohydrate their horse consumes? Should horses no longer consume grass? Does their horse need medication? How do you know if your horse truly has metabolic syndrome?
Classically, horses with metabolic syndrome are described by a certain appearance. They are typically obese horses which gain weight readily, and are considered “easy keepers”.   Breeds with a higher prevalence of metabolic syndrome include the traditional easy keepers such as ponies, Morgans, and Paso Finos. However, metabolic syndrome  can be seen in a wide spectrum of breeds including Quarter Horses, Arabians and Thoroughbreds.  Beyond just being obese, metabolic horses tend to have regional adiposity, or specific fat deposits on the crest of their neck, over their tailhead, the sides of their abdomen and also in the scrotal or mammary area.  The size of the crest of the neck is often the best physical predictor of metabolic syndrome. The thicker the crest, the more likely the horse truly fits into this category. However, it is important to note that it is possible for leaner horses to also suffer from metabolic syndrome. Despite being lean these horses still demonstrate regional adiposity, along with a susceptibility to pasture associated laminitis, as well as insulin resistance. Therefore, if your horse shows symptoms, it may be wise to have it tested, despite it not being overly obese.
Unfortunately the most common way horses are diagnosed with metabolic syndrome is the frequency of laminitic bouts. Usually this is seen following grazing on pasture, especially in the spring or fall.    These horses may be young or middle aged, which sets them apart from horses who suffer from Cushings disease. However, horses who suffer from metabolic syndrome early in life are certainly more likely to develop Cushings later on. Cushing horses are also distinct in the prevalence of hair coat which does not shed or long curly hair while the metabolic horse has a normal hair coat.
Physiologically, these horses demonstrate insulin resistance.   Essentially they must secrete larger amounts of insulin compared to a normal horse, in order to stabilize their blood glucose levels. Therefore, their insulin levels remain higher in their bloodstream, which can have a cascade of effects on their body. They also present with elevations in blood lipids, as well as an increase in leptin. Leptin is a hormone secreted by fat cells or adipocytes, that normally helps in the feeling of satiety (or fullness). However, increased concentrations of leptin may contribute to inflammation in the body. Metabolic horses also have a lower resting thyroxine levels (T4) then their normal counterparts. However, the low level of T4 does not cause insulin resistance and metabolic syndrome, but rather is merely a consequence of altered metabolic profiles.
So why are these horses so susceptible to laminitis? What could insulin resistance possibly have to do with painful feet? One of the commonalities between the myriad of disorders that can result in laminitis in horses is a disruption of the circulation to the hoof. Insulin is most commonly recognized for its role in glucose disposal, but it is a hormone with systemic effects. It is presumed that sustained hyperinsulinemia promotes vasoconstriction. It is already known that carbohydrate overload induces laminitis by creating vasoconstriction in the hoof, so the hyperinsulinemic horse may be even more susceptible to shifts in carbohydrate intake. This disruption of blood flow to the foot results in hypoxia and tissue damage to the sensitive laminae. Severe bouts may render the hoof wall unstable and allow the coffin bone to rotate downwards within the foot. This may lead to permanent alterations of the hoof structure.
Testing for metabolic syndrome frequently involves blood sampling after a short period of fasting (typically 6 hours). Blood is analyzed for glucose and insulin levels that are above normal. The presence of altered adrenocorticortropin releasing hormone can also be tested if Cushings is suspected in an older horse.   Further testing can be done if horse’s insulin levels are within the normal range, but metabolic syndrome is suspected. Horses are again removed from feed, and a standard blood sample is taken. Horses are then given a bolus of glucose and then insulin to determine how the body metabolizes these compounds. This provides a more dynamic picture of the horse’s metabolic response to carbohydrates.
If your horse has been diagnosed with metabolic syndrome, or has show signs of pasture associated laminitis, it is important to start them on a rigorous management protocol. First, as these horses have sensitivities to carbohydrates, concentrates should be removed from the diet. As these horses are typically obese anyhow, there is little need to supply concentrates to them anyhow. If the owner is concerned with mineral and vitamin intake, there are many products which are intended to complement forage only diets. Typically these are pelleted supplements which are fed at very low levels of intake. The obesity issue in the horse should also be addressed. Exercise should be increased to 5 days a week. Not only will this aid in reducing the body weight of the horse, but exercise also enhances glucose clearance from the blood in a non-insulin dependent manner. However, be sure that the horse is not recovering from any laminitic episodes. Pasture intake should also be limited in these horses. Horses should only have access to pasture for a short time or have access to a very small area. If more movement of the horse is desired, a grazing muzzle should be employed to prevent overconsumption of grass. The horse should receive an all forage diet, preferably of grass hay, with intake reduced in order to encourage weight loss. If weight loss is not able to be achieved at an intake of 2% of the body weight, then reduce feed intake to 1.5% of bwt. Unfortunately simple diet restriction may take a long time due to the efficiency of the horses prone to metabolic syndrome. If the horse has greater degrees of insulin resistance, it is advisable to monitor the non-structural carbohydrate composition of the hay, with it ideally below 10%.If horses have persistent issues with metabolic syndrome after calorie restriction, decrease in adiposity, alteration of diet, limitation of pasture intake and exercise have all been employed, then there are medical therapies which can be used. Levothyroxine is effective in improving insulin sensitivity. If all of these measures are followed faithfully, there is no reason that these horses cannot be returned to a metabolically normal state and enjoy a long healthy life.
Next month: We will discuss other strategies that have been employed to assist the metabolic horse.