Dr. Kris Hiney

  • Prebiotics in Horses

    Written By Dr. Kris Hiney

    Last month we discussed the use of probiotics in horses, including the definition and types of probiotics, their effectiveness, and when their use might be warranted.  This month we will address a closely related and often misunderstood topic: prebiotics.  The use of both of these feed additives may work synergistically to promote digestion in your horse, keep his immune system in top shape and allow him to face the various stressors which may be present in his life.

    As opposed to probiotics, prebiotics are not live organisms.  Rather, they are chains of specific types of carbohydrates which promote the growth of organisms which are beneficial to the well-being of the host.  Prebiotics are derived from a variety of products, including milk, fruit, vegetables and fermentation byproducts.  These are typically short chains of fructo-oligosaccharides (FOS), which are a mix of fructose and glucose, mannose oligo-saccharides (MOS) or galacto-oligosaccharides (GOS).  Simply stated, oligosaccharides are shorter chains of carbohydrates or saccharides (sugars) as compared to polysaccharides such as starch, glycogen of cellulose.  For a review of carbohydrate terminology, please see: Equine Carbohydrate Disorders Part 1. Because of the type of bonds joining the carbohydrates together, prebiotics are not able to be enzymatically digested in the stomach and small intestine.  Instead they provide substrates for fermentation of a specific group of bacteria and thus allow them to flourish.  It may be helpful to think about prebiotics as providing food for the good types of bacteria, rather than feeding your horse.   In ruminant animals such as cattle, sheep and goats, they have a direct effect on the rumen microflora, while in monogastrics and hind gut fermenters such as the horse, prebiotics pass to the hindgut where they exert part of their beneficial effect.   Horses also have a substantial microbial population in the foregut as well.  While the use of prebiotics in gastric health of the horse has not been explored, it does appear promising as a potential tool in maintaining stomach health.

    So why would you have to feed the bacteria?  Certainly a horse on a high forage diet would have adequate nutrient delivery to those microbes, correct?  Well, different types of organisms utilize different substrates for food.  If there is more food available for one type, they will be more successful and reproduce at a higher rate.  Cellulytic bacteria are responsible for fermentation of the fibrous portion of a horse’s feed and are typically associated with a higher pH in the gut.   However, amylotic bacteria prefer substrates such as sugars and starches. When we over feed concentrate to our horse or forages containing more rapidly fermentable sugars, these amylotic bacteria flourish and can produce negative by products for the horse.  Prebiotics typically provide substrate for more beneficial strains of bacteria including bifidobacteria (found more in humans), lactobacillus and lactate utilizing bacteria.  The use of prebiotics has shown to be effective in preventing the rapid and detrimental shift in bacterial population which occurs when horses are overfed concentrates. Now certainly it would never be advisable to subject our horses to a rapid increase in carbohydrates.  However, we could think of supplementation of prebiotics during periods of dietary adaptation, shifting to a new feed source or when starting to graze in the spring as a potential way to modulate gut microflora. However, supplementation of prebiotics would not be an alternative to slow controlled adaptation to new diets.

    Prebiotics may have more benefits than just helping to increase fermentation or stabilize the population of the hindgut.  While not digested in the small intestine, prebiotics help prevent the colonization of pathogenic bacteria such as Salmonella and E coli.  Doing so improves the overall health status of the animal.  They do so by binding to the carbohydrate receptor sites on the bacteria which are used to bind to intestinal epithelial cells. By “tricking” bacteria into binding to these oligosaccharides, they are prevented from binding to epithelial cells and proliferating. Promoting the growth of the beneficial bacteria may even limit the growth of pathogenic bacteria.  Bifidocacteria and lactobacillus possess their own bactericidal/anti-microbial effects against harmful bacteria. The “good” type of bacteria may also release enzymes which destroy the toxins produced by pathogenic bacteria.  Clearly it is easy to see why the feeding of prebiotics has gained much attention in feeding production species as an alternative to antibiotics.

    In addition to these direct effects on bacteria, immune-stimulatory effects of prebiotics have been observed in a variety of subjects. These appear to be not only in response to viral or bacterial challenge, but even with allergen stimulated immune responses. Human infants supplemented with prebiotics which mimic those found in breast milk developed fewer infections compared to those not receiving prebiotics.  There is also some evidence that intestinal epithelial cells may be able to transport prebiotic oligosaccharides, putting them in direct contact with cells of the immune system.  In an in vitro equine study, peripheral blood mononuclear cells (lymphocytes, macrophages) showed an increased immune response when these cells were cultured in the presence of GOS and FOS. When these same cells were challenged with LPS, the effect was even more pronounced in cells cultured with FOS and GOS.  The use of prebiotics may be a tool in helping to develop the immune system of neonatal foals, as has been proposed in other species.    Finally, prebiotics may serve as natural anti-oxidants themselves. In part this could help explain their immunomodulatory effects as well.  Therefore, consider using prebiotics when the animal might be undergoing periods of stress, as stress typically weakens the immune system.

    Even beyond their ability to affect the population of micro-organisms in the hindgut or stimulate the immune system, prebiotics may also help with insulin sensitivity.  This has been shown in dogs, veal calves, rodents and humans.   The effect is believed to be due to the alteration of fermentation in the hindgut, resulting in a shift in the ratio of volatile fatty acids which are produced. In obese horses supplemented with short chain FOS, a modest improvement in insulin sensitivity was observed after 6 weeks.  Prebiotics may serve as an aid to restoring insulin sensitivity, but certainly should not replace diet modifications or a sound weight loss program.

    Certainly the addition of prebiotics to the human food supply is increasing, and a number of products designed for use in pet foods and production animals point to the value of this natural foodstuff in promoting the health for all. There do not appear to be any risks associated with feeding prebiotics, and the number of proven health benefits is quite expansive.  The evidence for their effectiveness in improving the health and well-being is so many species of animals is substantial.  So if your horse needs help with digestion, stress, his immune system or even insulin resistance, consider a prebiotic.

  • Digestive Aids in Horses

    Written By Dr. Kris Hiney

    This month we will explore the use of digestive aids in horses, in particular probiotic usage. Probiotics are increasingly used in human medicine, production animal species, and of course in horses.  More owners are looking for safe and effective alternatives to pharmacological methods for promoting the well-being of their horses.   In this article we will discuss what type of organisms fall under the probiotic umbrella, the form in which they may be fed, their effectiveness and when their use might be warranted.

    In general, probiotics are live organisms which are fed with the intention of their survival within the gastrointestinal tract.  The original concept behind the use of probiotics was to provide a beneficial type of microorganism which can alter the fermentation process in the hindgut, or to shift the microbial population away from more negative types of organisms.  Typically these organisms promote digestion and alter the types of volatile fatty acids that are produced.  This was typically referred to as a competitive exclusion effect.  However, it is becoming more widely understand that probiotics may have farther reaching effects than just simply outnumbering undesirable bacteria.  This differs from when organisms are fed for their nutritive value, such as often done with yeasts.

    Horse owners have many options when selecting probiotics, including powders, pills, pastes, feeds, live culture yogurt or even innoculations of fecal microflora from healthy horses.  The key feature for a probiotic to be effective is that it is able to survive exposure to acid, bile and enzymes in the foregut of the horse and reach the hindgut alive.   In addition it must remain viable during processing and storage of the product. Further, microorganisms must be present in sufficient quantities to have an effect.   From extrapolations in human studies, it is suggested that foals be provided with a minimum of 10 to 20 billion colony forming units or CFUs with some studies suggesting an increase of 10 fold in adults.  Therefore concentrated forms of probiotics are often the most effective, rather than just a feed with added probiotics which may contain insufficient organisms.  It is highly recommended that horse owners read product labels carefully in choosing a digestive aid for their horse to ensure the product contains living organisms at sufficient numbers.  Unfortunately many commercial products may not actually even contain the amount of microorganisms listed on the label.  In a study from 2002, products contained as little as 2% of the CFUs claimed on the label.    In addition, some claims may be misleading and actually only contain fermentation products, which are not live cultures and therefore not probiotics.

    Beyond viability and amount of probiotics, the type of organism contained in the probiotic is key.  The most common classes of probiotics are the lactate utilizing bacteria including lactobacilli, bifidobacteria and enterococci. These bacteria are those that convert lactate to propionate in the gut which may help stabilize colonic pH.   Live yeast cultures have also been used, in particular Saccharomyces cervisiae.  This differs from the use of yeast products which may be fed in order to supply vitamins or protein from the process of digestion of the yeast itself.  When looking for a yeast supplement intended to be a probiotic, be sure that it actually contains live yeast   Most species of organisms in probiotics are not typically found inhabiting the gut of the horse. Thus they fail to form permanent stable colonies in the gut, and will no longer be present after administration has been ceased.  Therefore continual supplementation may be necessary depending on the desired outcome.

    Live yeast and bacteria supplementation may have beneficial effects beyond that of just supplying a different microorganism with fermentative capabilities.  Some yeasts may release enzymes which digest the toxic by-products of pathogenic bacteria.  It is also believed that yeasts and lactate using bacteria may have immunostimulatory effects, stimulating the gut associated lymphoid tissue.  This enhances the immune system of the horse and may make them more capable of handling exposure to pathogens. Other pathogenic bacteria such as Salmonella and E coli may bind to the yeasts rather than the epithelial tissue of the gut, thus preventing their colonization. Supplementation of live yeast has also been shown to improve digestibility of fiber and increase the amount of lactobacillus in the hind gut which again may be protective against acidotic conditions in the hindgut.

    Probiotics are frequently administered when there is believed to be a disruption in normal gut microflora, such as during bouts of diarrhea, following anti-biotic administration or other gastric upsets.  This can include any stressful period for the horse such as travel, new environments, or alteration in diets. Horses supplemented with yeast and subjected to transport had greater biological diversity of bacterial species in the hindgut, and an increase concentration of lactate using bacteria and cellulytic bacteria.  Thus these horses maintained a healthier hindgut population compared to non-supplemented controls.  Supplementation of live boulardii yeast, a sub species of Saccharomyces cervisiae resulted in a shortened period of diarrhea and a quicker return to normal feces in horses suffering from enterocolitis compared to a placebo group.  Horses in this study had a broad range of causative factors for the diarrhea.  Thus probiotic administration may be an additional therapeutic tool in managing colitis or diarrhea in horses.    Probiotics may also reduce the detrimental effects of a high starch diet on the microbial population.  Typically high starch diets promote the growth of amylotic bacteria and decrease the population of cellulytic bacteria, thus suppressing fiber fermentation.  In addition, the by-products of amylotic bacteria are responsible for lowering the pH of the hind gut.  If probiotics are used in conjunction with higher concentrate diets, the overall health of the gut may be improved.

    So when is a probiotic right for you?  Certainly during periods of digestive upsets, probiotics can help return the microbiology of the gut of the horse to a healthier state.  They may also assist a horse during times of stress, not only preserving the health of the GI tract, but also the health of the horse itself.  Probiotics promote a stable pH in the gut and can assist in fermentation in the gut.  There a very few negative indicators for probiotic usage, rather just be sure that you choose an effective product.

  • Water Losses in Horses

    Written By Dr. Kris Hiney

    This month we will discuss the most important nutrient in your horse’s diet, but maybe the most overlooked. Because providing our horse with water may seem obvious, many believe water requirements may not warrant discussion. But how much do you really know about how much your horse should be drinking per day?

    The amount of water a horse needs to consume per day is directly related to how much water the horse loses per day. Horses lose water through four ways: their manure, urine, sweat, respiration, and if a broodmare, lactation. All of these variables must be taken into account when determining how much water our horses should be drinking. When we increase these losses due to variations in diet, work or environment, we must allow the horse greater access to water. Sometime that may mean we need to be creative in encouraging the horse to consume more water.

    One of the greatest water losses to a horse is often overlooked, horse manure. While we tend to think of it as a rather solid form that we must continually scoop, pick up or shovel, horse manure is mainly water. This is especially true if the horse is eating primarily roughages. On an all forage diet, horse manure contains as much as 72-85% moisture. In fact, the water lost through their manure may represent almost 60% of a horse’s daily water intake. If we switch the horse to a grain based diet, the manure actually becomes much drier. Now, that does not mean that this may be a great strategy to minimize water losses. Overly dry feces can lead to impactions and colic, which is certainly to be avoided! When a horse consumes forage, it must be digested through fermentation which requires a fairly liquid environment in the hindgut and therefore normal gut health. In part, this is why it is recommended to always provide at least 1% of a horse’s body weight in forage per day. Consumption of forage therefore encourages water intake.

    Variations in diet beyond just forage versus grain, can influence water losses in horses. The total amount of feed the horse eats will alter its water requirements. As consumption of feed increases, the horse must consume more water in order to allow normal digestive processes to occur. While we mentioned already that forage does increase water losses and thus water intake, the type of forage the horse consumes alters its water needs. Obviously fresh pasture grass contains a much higher moisture content compared to dry feed which is typically only 10-15% moisture. Growing grass may contain as much as 80% moisture. When taking into account the total amount of grass a horse can consume, simple grazing may approach a horse’s basic water requirements. Don’t be surprised then if your horse visits the water trough less frequently while he is grazing compared to when you feed hay.

    Urine obviously contributes to water losses in horses, but remember that the volume of urine may reflect the water balance in the horse. Urine actually represents the most variable water loss in the horse, as other losses are more directly tied to diet, metabolic demands and environment. Some horses simply consume more water than others, and as a result will excrete more dilute urine in order to rid the body of excess water. Alternatively, if we fail to adequately meet our horse’s water needs, the kidneys will act to limit water losses and concentrate the urine. Additionally, if the feed contains components that need to be excreted by the kidney, water losses will increase. For example, when horses are fed protein beyond their requirements, the extra amino acids are broken down into components that can be used for fuel. This process involves the removal of the nitrogen found in amino acids. The kidney incorporates the excess nitrogen into urea, which is then excreted through the urine. Excess electrolytes, in particular sodium and potassium, must also be excreted by the diet. If you have a horse that likes to consume his salt at a greater rate, you may notice that his stall may be wetter than horses which do not perform such a practice. If you own an enthusiastic salt eater, you may want to limit his intake to strictly his salt requirements.

    Sweat represents a tremendous variable in water losses for the horse, dependent on temperature and exercise. Remember that horses are most similar to humans in that we both dissipate heat through sweating, compared to other species that may rely primarily on respiratory cooling or panting. As horses must breathe through their nostrils, panting is simply not an option for them. Increasing the environmental temperature can increase evaporative losses between 45 to almost 400% of the horse’s normal water losses. The addition of exercise on top of environmental losses can quickly lead a horse to dehydration and heat stress if water losses are not replenished. For example, cross country horses have been reported to lose as much as 50-75 lbs of water during a competition due to the sustained duration of activity. Respiratory water losses are also directly tied to temperature and work load as these have the greatest influence on respiration rate. Horses increase respiration rate, either to aid in cooling, or due to the increased demand for oxygen delivery to the muscle tissue. However, relative to sweating, respiratory losses are relatively minimal.

    The good news is that horses, through training or adaptation to their environment, do become more efficient at heat dissipation and begin to minimize their water losses. However, full acclimation to increased environmental temperatures may take up to 3 weeks. While it would be nice if weather patterns would gradually increase over time allowing our horses to adapt, we all know that this is simply not reality. Therefore, when the temperature gage rises dramatically, or even sporadically, we must acknowledge that our horses may not easily be able to dissipate heat. This will require more caution on our part when working our horses during this abrupt changes in temperature.

    Lactating mares also have a significant loss of water through the milk. The amount of milk produced can be very variable between mares, with an average of 2 to 3% of their body weight per day. This will increase their water requirements somewhere between 50 and 75% over their normal requirements. If we also remember that lactating mares have a very high energy demand on their bodies, their feed intake increases as well. Remember that as feed intake increases, the horse must increase their water consumption to maintain digesta flow, and to counter the losses of water through the manure.

    So what does all of this mean relative to what we need to offer our horses? My basic recommendation is to always allow the horse access to water beyond what they are willing to drink. In general a horse will consume around 10 gallons of water per day. This is easily accomplished by offering two full buckets twice a day. However, if you find that the bucket is empty when it is time to refill it, consider hanging an additional bucket. Your horse will thank you!

    Next month we will delve more deeply into the current research on strategies to maximize your horses water intake. We all are familiar with the adage that you can lead a horse to water but you can’t make them drink. However, sometimes we really need them to drink! We will also discuss some feeding strategies that may help your horse stay hydrated through the various activities he may encounter such as traveling, endurance exercise, or exercise during hot temperatures. Remember, there is more to know about water than just filling a bucket!

  • Does the Season Affect Your Feeding Management?

    Written By Dr. Kris Hiney

    Does the season affect your feeding management? Winter is the season of short days, long cold nights and reduced riding time for us and our horses. Often what we feed our horses in the winter shifts as their energy requirements change, as well as the feedstuffs we might be using. That shift in seasons may mean we need to look at our feed sources and our supplement regimen more closely.

    To begin our discussion, remember that a horse’s energy requirements do change with the seasons. Cold weather creates additional caloric demands on the horse’s body in order to regulate its body temperature. When temperatures drop below a certain point, referred to as an animal’s lower critical temperature, it must expend more energy in order to maintain its own body temperature. For horses which are acclimated to cold temperatures (meaning we have allowed them to grow a hair coat and they have been housed outdoors), this lower critical temperature is usually around 5° Fahrenheit. When temperatures drop below this point, we really should be feeding our horses more. In general, for every two degrees drop in temperature, the horse needs 2.5% more calories to maintain its’ body temperature. Therefore, if it gets down to about 10 below, your horse will need 20-25% more feed! These numbers do not consider wind chill factors, which can drive up heat loss substantially. Bottom line, in light of this year’s extreme cold, if your horse is living outside this winter, you may find yourself going through your hay supply much faster than you had anticipated.

    How you choose to supply that energy to your horse may be important as well. There are several strategies which may be employed to augment your horse’s calorie deficiency. One easy way to meet energy requirements, along with adding to the heat produced by the process of fermentation in the hindgut, is to simply feed more hay. Consumption of hay has a higher heat increment (or heat associated with digestion) than other feeds, therefore it helps to keep your horse warm at the same time. In addition, more calories can be provided by choosing a higher energy concentrate, such as one with higher concentrations of fat. There are many commercial feeds available with added fat, or choosing rice bran or a flax source may be an option. If choosing a fat-added feed, it will provide more calories to the horse without having to increase as greatly the volume of feed that you are using. Many horse owner’s also like to add warm mashes to their horses diet in the winter. This provides more energy to the horse as bran or pellet mashes are higher in caloric density than forage. The additional benefit is that you can increase your horse’s water consumption, which may have decreased in the winter if they do not have access to heated water. Finally, it just may make you feel good to feed your horse a nice warm mash on those cold days and nights.

    Obviously the manner in which we feed our horses also changes with the season. Ideally, horses are allowed opportunities to graze pasture grass in the temperate part of the year. However, with the fall and winter, horses in northern climates much be switched to an all harvested forage diet. While many of the nutrient components in harvested forage may be completely adequate for your horse, realize that the composition of plants does change with advancing maturity. In order to be tall enough to produce hay, grasses and legumes must reach a more mature state than a horse would typically select left to its own devices. In addition, some nutrients, such as vitamin A, do diminish over time. In particular, omega three fatty acids are found in smaller quantities in hay than in fresh growing grass. As we have changed how we manage all of our production animals and switched to more grain based diets, they now consume much more n-6 fatty acids versus n-3 fatty acids than when they were more pastorally raised. In fact, knowledge of the higher content of n-3 fatty acids in grass is in part what has led to the rising consumer popularity of grass fed beef. Grazed cattle consume much more n-3 fatty acids compared to traditionally raised feed lot cattle which have diets much higher in n-6 fatty acids. The diet the animal is on directly influences the n-6 to n-3 fatty acid ratio in their body tissues. Diets higher in n-3 fatty acids have been shown to be anti-carcinogenic, anti-inflammatory and cardio protective. While we may not think about horses in quite the same way, or feed them a concentrate based diet like feed lot cattle, the same process of incorporation of more n-3 fatty acids into their tissues occurs when horses graze or are supplemented with n-3 fatty acids. Ideally, our horses also should be consuming more grass and n-3 fatty acids, and less n-6 fatty acids which are found so abundantly in concentrates. However, even switching to a harvested forage based diet can alter the n-6 to n-3 ratio compared to a fresh grazing. Hay making can result in a loss of fatty acids of more than 50%, especially of linolenic acid, with a comparative increase in n-6 fatty acids. In a study using ewes, grass fed ewes had more milk and tissue n-3 fatty acids than ewes fed a hay diet. But obviously we cannot always feed grass to our horses. Therefore, in order to mimic the natural diet of the horse, and provide them the positive benefits of n-3 fatty acids, we can supplement them in other ways. Flax is a rich source of linolenic acid which horses readily consume. Therefore, in the winter, why not try a flax supplement and at least return your horse’s diet to summer, even if the wind is still howling!

  • Colic Prevention Part 2

    Written By Dr. Kris Hiney

    This month we will finish our discussion of common causes of colic in the equine, and what you might do to prevent them. Previously we discussed the importance of having a thorough emergency plan in place in order to make a potential colic less stressful for you. We followed that with a discussion of the most common management practices which will help minimize your horse’s risk of colic. These included quality and consistency of the diet, proper hydration and parasite control to name a few. This month we will focus on some of the less common reasons horses may colic. Although less common, they are no less important for the owner to be aware of these possibilities.

    The sex of your horse may increase its likelihood of colic. Remember that colic just refers to general abdominal pain. Some mares experience discomfort relative to their estrous cycle. If your mare routinely shows mild colic at three week intervals, her ovaries may be the culprit. Normally cycling mares will ovulate every 21 to 23 days and this event can be associated with discomfort. Having a reproductive exam can also rule out if she has an ovarian dysfunction exacerbating her discomfort. If you choose to breed your mare, you must also be aware of the possibilities of colic associated with pregnancy. During gestation, the mare may experience colicky symptoms due to movement of the fetus. That does not mean that colic signs during gestation should be discounted. Follow your normal procedures of a thorough exam and consult with your veterinarian. Finally, mares are often crampy after foaling, as the uterus continues to contract in order to expel the placenta. Additionally there is a greater potential for twisted bowels post foaling due to the extra “room” in the abdominal tract. Typically these mares will experience very severe pain. As I have personally had to suffer the loss of a mare with a new foal at her side, realize that these are very real possibilities. Monitoring mares closely in the post foaling period may allow you to catch symptoms early and perhaps save her life. All in all, realize that there are risks one has to assume when choosing to breed horses.

    The lifestyle of your horse may also cause it to colic. Some horses experience far more stress due to competition or travel than other horses. Some horses dislike horse shows or competitions so intensely that they work themselves into spasmodic colic. If this is true, you really need to closely examine why your horse is experiencing stress. Are you asking too much of them? Do you warm-up or ask the horse to perform at a different level than at which you train? Is the change in environment or the close proximity of other horses too much? Try to acclimate the horse gradually to stressful scenarios. Be reasonable in your expectations of your horse. Consider how nervous or anxious you may be at shows. Isn’t it likely that your horse may also experience anxiety (albeit for perhaps different reasons)? Ultimately, it may be possible that that type of career may not be a great fit for your horse. Consider a less stressful type of competition or even re-homing the horse where it may be more comfortable. After all, competitions and events serve as recreation for most horse owners. Is it really fun if your partner is miserable?

    When traveling to events, also consider how long the horse is in the trailer. Hauling in a horse trailer for long periods of time is actually fairly tiring for the horse. Ideally you should let the horse rest every 5-6 hours. Coupling that with a change in a horse’s normal feeding schedule and reduced access to water, can set the horse up for colic. At rest stops, consider offering your horse flavored water to ensure he maintains his water intake. Begin to accustom him to the flavoring at home to ensure he actually likes it. This is especially critical in hot weather, when the temperature in the trailer can exceed the external temperature. Horses may lose a substantial amount of water through sweating that they may not have the opportunity to replenish. Horses may also be more likely to develop respiratory issues while confined in a trailer as well. While we often try to help the horse by keeping hay in front of them, open windows or sides can force dust and particulate matter into the horse’s airways. This can cause the horse to develop pleuritis, which is inflammation of the lungs. While it is a respiratory issue, the horse may still show colic-like symptoms. All in all, plan your travel with your horse’s comfort and health in mind.

    What breed your horse is may also pre-dispose him to certain gastrointestinal disorders. Arabians and Arabian crosses are more likely to develop enteroliths than other breeds of horses. Enteroliths are essentially an accumulation of mineral within the intestine which forms a rock-like object. This can range in size from very small to the size of a softball or larger. While the reason is not yet known, this risk increases when these horses are fed alfalfa. This is especially true in the California and in other parts of the Southwest. However, this does not mean that a Quarter Horse in Iowa can’t develop an enterolith, they are just less likely to do so. High alfalfa diets are thought to cause enteroliths due to the high level of magnesium and protein combining to form crystals which make up the enteroliths. Diets higher in wheat bran have high levels of phosphorous which also contribute to enterolith formation. It is also possible that feeding highly digestible, lower fiber feeds like alfalfa may reduce gastric motility, allowing crystals to form more easily. Other lifestyle factors which lower gastric motility, such as lack of exercise or low frequency of feeding, increase the risk factor of enteroliths. Even the type of bedding chosen to be used can affect a horse’s risk of developing enteroliths. Horses on straw bedding, which allows an opportunity to nibble on high fiber feedstuffs, experience less enteroliths. While many believe that adding vinegar to the horse’s diet to lower colon pH may prevent enterolith formation, this has not been proven. Ideally, lower the amount of alfalfa in the horse’s diet, feed frequently and allow ample exercise are the best management choices.

    While we can never completely ensure that our horses will never colic, following practical management strategies can lower these risks. Informed horse owners are those whose horses usually experience less health issues. Hopefully if you follow these tips from our last series you can have a colic free 2014! Until next month, enjoy some winter riding!

  • Strategies to Reduce your Horse's Chance of Colic

    Written By Dr. Kris Hiney

    Last month I encouraged all horse owner’s to develop a preparedness plan in the event their horse colics.  This month we will discuss strategies that will hopefully minimize the chance that you will need that plan.  We will discuss feeding strategies as well as other important management techniques that will help keep your horse happy and healthy.

    Feeding your horse properly is one of the easiest ways to help prevent episodes of colic.  Remember  the digestive anatomy of the horse, with its small stomach and large hindgut for digesting forage does not often fit well with  modern management practices.   The horse is designed to forage continuously throughout the day, typically for almost 18 hours.  This provides a continuous input of material to the hindgut without overwhelming the stomach.

    1.Maximize intake of good quality forage.

    To mimic nature, ideally a horse should consume 2% of its body weight in high quality forage per day.  This allows the best match to the horse’s normal feeding strategies.  Remember high quality forage does not necessarily mean rich or high energy forages which can lead to obesity.   Simply put, high quality hays do not contain molds, potentially toxic weeds or insects, or are not excessively coarse and stemmy.  Of course, toxins and molds can easily cause digestive upsets or result in feed refusals.

    2.Avoid very coarse hay or staw as feed.

    Excessively coarse hay may be harder for the horse to masticate and may lead to impactions.

    3.Prolong feeding/chewing  time.

    If your horse needs to consume less than 2% of its body weight due to the need to maintain proper body condition, using a slow feeding hay net will help prolong the horse’s feeding time.  As we increase the amount of time the horse spends chewing, more saliva will enter the stomach and buffer the acid that is continually secreted.  As horses only salivate with oral stimulation, this increase in chew time is extremely important.  This helps to maintain a healthy stomach and avoid ulcer formation.

    4.Split up concentrate meals to smaller portions.

    If the horse needs substantial amounts of concentrates in order to maintain body condition or support athletic performance, be sure to spread feedings into smaller amounts.  High volumes of concentrate may overwhelm the horse’s ability to digest it properly in the small intestine.  When concentrates escape to the hindgut they are fermented by a type of bacteria which produces organic acids and lowers the pH of the horse’s gut.  By lowering the volume fed at one time, this will avoid fluctuations in pH of the horse’s tract and promote a healthier population of microflora.

    5.Slowly introduce new feeds.

    If new types of feeds are to be introduced to the horse’s diet, be sure to do so gradually to allow time for bacteria to adjust.   Due to the ability of bacteria to either proliferate or reduce in population with changes in substrate offered to them, a change in the horse’s diet can wreak havoc in bacterial populations. Often this is what results in the overproduction of gas, a frequent cause of colic.

    6. Maintain a consistent feeding schedule.

    If your horse does not have free choice access to hay or pasture, be sure to maintain a consistent feeding schedule.  Horses are certainly creatures of habit that do best with consistent schedules.  This will avoid periods of time with the horses’ stomach in an unnatural empty state, or overeating due to excitement of feeding.
    7.Avoid feeding horses off the ground.

    Ingestion of sand can lead to the development of impactions or colitis from irritation of the gut wall.  Routine feeding of psyllium can aid in sand removal from the hind gut.  Feeding off the ground will also limit the exposure to parasites which are a frequent cause of colic through either blockages or disruption of blood flow.

    8. Practice strategic deworming and parasite management.

    Regular parasite control is therefore key to colic prevention.  Remember from previous articles that this does not mean indiscriminate deworming of horses without knowledge of their true parasite load.  In fact, an increase in colic in young horses due to ascarid impactions may be in part due to the anthelmentic resistance occurring in these worms.   Rather, remember to follow strategic deworming practices in consultation with your veterinarian.   Follow good pasture management practices and avoid overgrazing. This will help to limit your horse’s exposure to parasites.

    9. Allow adequate water intake.

    As winter approaches, it is especially important to remember that proper water intake is vital to maintaining normal flow of digesta through the horse’s tract.  Normally horse’s drink about 8-12 gallons of water per day.  We often think about increasing a horse’s water intake when it is hot or the horse is heavily working, but fail to think about water intake in the winter.  Horse’s actually don’t like cold water, and will greatly reduce their water intake if not offered warmer water.  Providing a heated bucket or tank will encourage your horse to drink water at the same rate throughout winter.  Be sure that it isn’t sending off any stray shocks however!  That will easily lead to dehydration as the horse is too frightened to drink!  You can also increase a horse’s water intake by offering a mashed feed.  Don’t forget however not to rapidly alter his diet!

    10. Provide regular dental care.

    While all of these tips primarily refer to the feeding management of the horse, other factors can influence his risk of colic.  Providing regular teeth maintenance will allow your horse to chew his feed properly.  As mentioned previously, coarse hay or poorly chewed hay can create impactions in the horse’s tract.

    11. Exercise the horse on a consistent schedule.

    Regular exercise for stalled horses is equally key.  Horses naturally travel several miles per day while foraging. We have created a rather artificial, sedentary life style for most of our horses. It is up to us to help provide a form of regular exercise and stick to a schedule.  While this may be difficult owners, it truly is best for the horse.   In fact, some companies are working towards creating automatic feeders which force a horse to travel through its paddock to obtain its feed. Such systems also have the added benefit of prolonging feeding time as well.

    Next month we will discuss additional management strategies that will reduce your horse’s risk of colic which are linked to your horse’s lifestyle, breed or even sex!

  • Equine Colic: Are You Prepared?

    Written By Dr. Kris Hiney

    Most horse owners at one time or another have experienced that dreaded sight of finding their horse rolling or kicking at their belly in their pasture or stall.  After all, almost 1 million horses colic in the United States each year, or about 11 in every 100 horses. It really is not a matter of if, but when a horse in your care will colic.  But now is not the time to panic, but to act logically and calmly.  The keys?  Be prepared, and have a plan.  This month we will discuss what symptoms you may see, what to do, and how to create a firm plan of action.  Next month we will discuss several important strategies you may implement to decrease the likelihood of your ever needing this plan.

    First of all, horses can colic for a variety of reasons. As colic just means a generic abdominal pain, any discomfort in the organs associated with the gastrointestinal tract can be described as colic.  Even other organs, such as the ovaries or uterus in mares, can causepain and thus may show symptoms of colic. So what may lead you to suspect your horse may be colicking?

    My first and strongest recommendation is to know your horse. Every horse has individual quirks of behavior, appearance etc.  The key to successful outcomes in colic, or in many cases of disease or injury, is catching a change quickly.  Any change in a horse’s normal behavior or appearance should immediately trigger a thorough investigation of the horse by the owner or manager.  So what might the horse be doing differently? Colic symptoms can range from the subtle to the severe and downright alarming.  Typically the severity of the colic will mirror the severity of the symptoms, but that is not always true.  Individual horses have a greater or lesser degree of pain tolerance. It is important to know if your horse is the stoic individual that works through an injury, or the type that becomes hysterical if they stubbed their hoof on a ground pole!  Subtle signs include horses which are off feed or water, but may not yet be completely refusing to eat or drink.  A change in behavior, being more depressed, less active or having a duller appearance may be signs of colic. Horses which are restless, or perhaps laying down more than normal, or laying in an unusual position may be colicking.  Pay close attention to foals, as foals can quickly develop abdominal discomfort related to disease, diarrhea ulcers etc.  A foal lying on its back is certain to be experiencing some sort of abdominal pain.  As pain becomes more severe horses may continually look at their belly or flank, kick at their abdomen, repeatedly get up or lay down.  They may begin to roll or thrash violently and can even injure themselves.  In severe pain, horses may break out into a sweat or grind their teeth together.

    Depending on the severity of the colic, your next step is to step in and gather some information.  Obviously, if your horse is in uncontrollable pain, call the veterinarian immediately.  Otherwise, if you can safely evaluate your horse, perform a physical exam on your horse.  That will help your veterinarian know how soon they may need to arrive.  Record your horse’s heart rate, respiration rate and temperature.  It is important that you practice these techniques before you need them!  A horse’s heart rate can be detected in a number of locations, near their eye, under their jaw, on their pastern etc.  Make sure that you have a working thermometer. Now is not the time to discover a dead battery in your thermometer.  Listen to your horse’s abdomen to hear if there is the normal gurgle of healthy gut movement.  An absence of sound indicated gut motility may have ceased.  If you horse is stalled, check his manure. Is there as much as there should be?  What consistency is it? Is it drier or harder than it should be?  How much feed has the horse eaten since his last feeding?  Is his water consumption normal?  Finally, check your horse’s gum color and capillary refill time.  Pale white or blueish gums may mean the horse is severely dehydrated, or may be going into shock.    This information may be critical in making decisions that may save your horse’s life.

    Now that you have some basic information, call your veterinarian.  It is important to have the veterinarian’s phone number readily available. Think about all cases of emergencies.  What if your cell phone has no reception or has a dead battery? Does your veterinarian make emergency farm calls? Will they be able to get here quickly enough to help you?  Discuss these issues with your veterinarian before colic strikes. They may offer some helpful advice on other colleagues they may trust when they may not be able to make the call.  Therefore you may want to post several numbers of veterinarians near your horse.
    You also need to do some hard thinking about the financial reality of colic cases. Some colics can only be resolved surgically.  Are you prepared for this?  Can you financially afford colic surgery?  Realize that is possible for colic surgeries to cost nearly $10,000.  Looking into an insurance plan for your horse can help cover major medical costs.  Do your research and see which plan may be best for you and your horses.  You may also need to at least consider that the outcome of surgery may not be positive.  Discussing these scenarios with family and your veterinarian before your horseever colics is critical.    It will make this emergency scenario much easier on you and allow you to make decisions more quickly.

    If you have made the decision that surgery is a viable option for you, add more details to your plan.  Do you have ready access to a truck and trailer? If you do not own your own, you need to have numbers of individuals absolutely willing to help, and located nearby, close at hand. The last thing you want at this point in time, is knowing your horse needs to get to a clinic, but you can’t find transportation.  Finally, know where the nearest veterinary hospital with surgical capabilities is located.  How long will it take to get the horse there?  This may affect your decision on when to load your horse on the trailer. Should you wait for your veterinarian to arrive at the farm, or should the horse immediately go to the clinic. Know where the clinic is located.  Now is not the time to be looking for directions or get lost in the middle of the night.  Practice!  The more that you have mentally and physically prepared yourself for these emergencies, the better the outcome for both you and your horse!
     

  • Strategies to Modulate Insulin Concentrations

    Written By Dr. Kris Hiney

    Much recent research in the horse industry has centered on fluctuations in insulin concentrations under a variety of conditions and the effects on the health of the horse.  Many horse owners are aware that traditional feeding practices which rely on a larger proportion of concentrate feeding may result in prolonged insulin secretion by the pancreas.  In young horses, it is thought that prolonged elevations in insulin may lead to cartilage abnormalities, promoting epiphysitis and osteochondrosis.  High starch diets are linked to behavioral issues such as more excitable or reactive horses;  and certain typing up disorders such as polysaccharide storage myopathy and recurrent exertional rhabdomylosis. Finally, high concentrate diets can certainly contribute to the development of insulin resistance and laminitis. As a result of this information, many  current horse feeds are now designed to minimize insulin fluctuations in the horse.  These feeds are typically low in traditional cereal grains such as corn and oats, may be higher in fat and fiber, or may be processed differently.   All of these techniques are designed to either minimize or slow the absorption of glucose out of the small intestine, and thus lower the need of the pancreas to secrete insulin to regulate blood glucose.  But what if switching feeds or eliminating concentrate is simply is not enough?  Are there other options available to the horse owner which can potentially help regulate insulin and glucose in their horses?
    One of the concerns for owners of insulin resistant horses is the frequent bouts of laminitis which occur if the horse is allowed access to pasture high in fructans.   Owners of these horses need to monitor their horses grazing carefully.  In order to avoid plants with high fructan content owners are advised against allowing access to pasture during the afternoon (when photosynthesis is at its peak rate), the spring, late fall or when grasses are stressed.  Further, warm season grasses offer a lower fructan concentration than cool season species of grasses and make better grazing choices for insulin resistant horses.

    But why are fructans such a concern?

    One of the theories addressing the laminitis inducing effect of high fructan content in plants is that fructans when consumed by the horse ,create changes in the bacterial population of the hindgut.  They undergo rapid fermentation, can alter pH of the gut and may result in bacterial endotoxin release.  However, this explanation does little to explain why insulin resistant horses in particular are so sensitive to fructans.  It may be that fructans trigger an increase in insulin itself that creates alterations to the vasculature of the hoof and the accompanying painful syndrome.   Insulin, while typically thought of as having a primary role in glucose disposal, has tremendous effects on the vasculature.  Insulin can act as both a vasodilator, or a vasoconstrictor.   Insulin resistance has been repeatedly been shown to cause cardiovascular dysfunction in many other species.  However, this role has not been fully explored in the equine.

    In attempt to explore this issue, researchers conducted a trial examining changes in insulin and glucose in horses allowed access to pasture during two different eight hour periods.  Horses were allowed to graze between 7 am and 3 pm or between 12:30 pm and 10:30 pm.   In this experiment, nonstructural carbohydrate content of the grass varied from 13.5% to 19.1% from 8 am to 10 pm.  The study did find a detectable, though not large, increase in insulin, in the horses fed during the afternoon grazing period when NSC values were there highest.   While the number of horses used in the study was small, and the grazing period did overlap, this study does indicate that the concentration of insulin in the horse may be sensitive to fructan content of grasses. The horses used in this study were also not insulin resistant horses.   Insulin resistant horses  may have differed in their insulinemic response to the feeding schedules.  However, this study may offer information as to why bouts of laminitis are triggered in the insulin resistant horse exposed to the wrong type of grasses.

    While we know that insulin resistant horses need to be stringently maintained on low soluble carbohydrate diets, other horses may benefit by paying attention to how we feed them.    While simply avoiding feeding grain may be an easy solution to avoiding insulin and glucose fluctuations, some horses  may require a diet higher in concentrates to meet their energy needs.  A common sense approach is to divide the horse’s meals into several smaller meals.  This is certainly an effective strategy in lowering glucose and insulin response.  However, one approach rather than running out to the barn multiple times per day to split up your horse’s meals, is to use a feeding system designed to slow down the horse’s consumption rate.  Researchers interested in this technique attempted to slow feed intake by adding grids to feed buckets, small hard balls or soaking the feed completely in water.   Using physical obstructions to feeding did prove to be successful  in increasing total feeding time, while adding water did little to alter consumption rate.  The best technique to lower insulin response was to add bocci balls to the bucket so that the horses had to move the balls around to gain access to the feed.  This idea has been elaborated to produce commercial feeding balls, which trickle out small amounts of concentrate as the horse rolls it about.  This also provides the added benefit of increasing the mental stimulation of the horse simultaneously!

    An interesting new theory is that perhaps the stress we expose our horses to may contribute to elevated insulin levels.  Chronic stress does increase cortisol concentrations which may have inhibitory effects on insulin, thus creating a greater need for insulin secretion, or in essence an insulin resistant horse.  In humans, stress and high cortisol can result in insulin resistance and a shift in the deposition of fat in the body. Perhaps stress in horses may also be contributing to insulin resistance and why we see regional adiposity in these animals.  In an initial foray into stress evaluation in horses, researchers examined whether different feeding schedules resulted in an elevation in cortisol.  However, in this study feeding schedules were not a sufficient stressor to elicit any dramatic increase in cortisol.   It is interesting that equine researchers are starting to look in new directions to solve the puzzle of insulin resistance in the horse.  While at this time, the effect of stress on cortisol and thus insulin in the horse is just a theory, maybe it wouldn’t hurt us to avoid stressing our horses unnecessarily!

    Much about insulin resistance and developing best practices still remains unknown.

    For example, in a study in which pregnant mares were fed high concentrate diets and gained rapidly in body condition in the last trimester of pregnancy, foals from the grain fed mares were actually more sensitive to insulin and had lower resting blood glucose. This does indicate that fetal programming, or the in utero environment can have long lasting effects on the offspring, but not what management protocols may be best are unknown.  While we have learned much about insulin resistance in horses, so much remains unknown. We often have to look at studies in other species and try to extrapolate this information to our management practices.  So over all, the willingness to try new methods and incorporate new information may be our best option.  Continue to monitor grazing tightly in insulin resistant horses, get creative when feeding grain, and don’t stress your horse!

  • Pasture Grasses and Grazing

    Written By Dr. Kris Hiney

    This month we will review research concerning pastures and foraging behaviors in horses. Most horsemen would agree that horses grazing at pasture represent the most natural way to feed a horse.  Certainly it represents the most economical and the least labor intensive method of feeding.  However, many owners have questions related to what or how much a horse’s is consuming when its primary source of feed is pasture grass.

    This ambiguity of how much grass a horse may consume makes selecting additional concentrates or supplements more of a challenge.  In addition, many horses clearly volunteer to consume pasture grass well over their nutritional needs making regulation of body condition score very difficult.   The range of dry matter intake of horses on pasture has been reported to be as wide as 1.5 to 3.1% of their body weight in a 24 hour period. Usually young horses and lactating mares will be on the upper range of intake which would make sense due to their nutritional demands.   Mature horses are reported to typically consume 2-2.5% of their body weight in dry matter.  However, it does appear that many of our equine friends have failed to adhere to book values when given the opportunity.  A recent study looking at weight gain in pastured ponies found that on average the ponies consumed 3.8% of their body weight in dry matter, with ranges of 2.9 to 4.9%.  Others have also reported horses consuming as much as 5% of their body weight in dry matter! It is rather easy to see why horses can quite easily gain weight on pasture.

    But what about horses which are only turned out for part of the day in an attempt to control feed intake? Is this an effective technique or do they simply manage to eat faster in their allotted grazing time?  In a study which attempted to determine how much a horse can consume in an 8 hour period, horses were individually assigned to small paddocks, allowed to graze for four hours, then switched to a new paddock for an additional 4 hours. The small paddocks were then harvested to determine how much the horses consumed in the given time period. In this experiment horses were able to consume 1.3% of their body weight within an 8 hour period.  In addition, their consumption rate was twice as high in the initial four hours the horses were allowed access to grazing. Therefore the horses were able to consume almost 1% of their body weight in just four hours!  Thus even limited grazing can easily result in weight gain.  From this data the authors concluded that for these particular grazing horses, only 9 hours of grazing was necessary to meet their energy needs.


    While we know that good quality pasture can easily meet a horse’s maintenance requirements, does it provide additional benefits to the horse?  In a study designed to look at the effectiveness of pasture turnout in maintaining fitness, horses which has been ridden 1-2 hours per week, 5 days per week for 12 weeks were then stalled, continued to be ridden or were turned out in a large pasture.  After a 14 week period, all horses participated in a standard exercise test.  This proved that the horses allowed free access to wander through a relatively large pasture maintained their fitness compared even to the horses ridden 5 days per week.  Thus pasture turnout seems to be a reasonable solution during down time when the horse is not ridden for maintaining fitness. The pastured horses in this study traveled on average 10 km a day compared to 5 km per day in the horses which were ridden.  This study again lends support to the value of pasture turnout.

    So what if we want the fitness benefit of pasture turnout without the obesity inducing over consumption?   Often the traditional answer has been to employ a grazing muzzle. In a study looking at intake rates in ponies wearing muzzles compared to their non-muzzled counterparts, muzzling resulted in an 83% decrease in overall intake. However, in just three hours, the non-muzzled ponies were able to consume 0.8% of their body weight in dry matter.  This is quite similar to the observations in the previous studies.  In addition, the same team of researchers found that the ponies “grew wise” to their limited access to grass and learned to increase their consumption rates during their restricted period.  Therefore limited time on pasture may not be as effective for foxy ponies once they learn what you are up to!  So what is our take home message?  Allowing horse’s time to graze is very beneficial, not only for their mental health, but also for their physical health.  However, in order to control intake and thus body condition score in our enthusiastic eaters, we made need to employ additional measures such as limited turnout or grazing muzzles.

  • Equine Research: Protein

    Written By Dr. Kristina Hiney

    This month I will begin a new series which tries to summarize some of the new information which has been gathered in equine nutrition.  I will be grouping similar topics together and trying to summarize how this information might be relevant to you and your horse.  We will discuss if this new information means you should change what you have been doing, or you can feel reassured that you are right on track!  And remember not all information may be relevant for your horse.  There is no need to feed your mature gelding who is trail ridden on the weekend like an endurance horse preparing for a 100 mile ride!

    This month we will focus on some new information on protein nutrition in the horse.  Certainly this is the time of year when many of us are busy procuring our hay supplies for the upcoming year.  Often we want the very best for our horses, and typically look for high quality alfalfa hays.  But is that necessary, especially in a year where the weather does not cooperate and hay selection may be more limited?  In a study using mature idle geldings, the digestibility and usefulness of protein from a variety of hays was tested.   Horses were fed diets of either  mixed grass hay alone, the mixed hay with increasing amounts of oats, or alfalfa hay that was either early bloom, mid bloom or late bloom.  As the maturity of alfalfa hay increases, typically its protein content decreases.   Therefore, many horsemen prefer earlier bloom alfalfa.  But is this necessary? In this particular study the horses were also fed at just 1.6% of their body weight as fed, which is typically a little lower than most people feed.  Thus these horses might have been fed at a lower rate than the average horseman would feed.    As expected, the protein intake of the horses increased as they were fed the alfalfa hay, with increased protein intake the earlier the stage of maturity. The digestibility of the protein in the diet also increased when fed straight alfalfa compared with the mixed hay, and digestibility was greater with less mature alfalfa.  That does reconfirm our knowledge that forages of later maturity are indeed less digestible.  However, the nitrogen retention between the groups of horses was not different.  Nitrogen retention refers to how much nitrogen remains in the horse’s body.  So if the horse’s nitrogen intake (which is reflective of protein intake) was higher, but the nitrogen did not remain in the horse’s body, where did it go?  The extra nitrogen was actually excreted in the urine.  You may remember from our earlier series on protein nutrition that excess protein consumed cannot be stored in the horse’s body. Instead, the nitrogen is removed from the amino acid, and the remainder of it can be used for energy or stored as fat.  Overall, for mature idle horses, there is no need to feed these higher “octane” hays, as it all that extra protein just ended up back on the ground!  There was no value to the horse in these high protein hays.

    However, what if you are not feeding a mature, idle horse, but instead are feeding mares and foals?  Their protein requirements are undoubtedly quite higher.  But it is not just protein quantity we must consider, but also the amino acid profile of the diet.  You may remember from previous articles that equine nutritionists have only described the requirements for lysine in the horse.  This is in stark contrast to other species in which the complete amino acid requirements have been well defined for  both growth and lactation. In other species, lysine is also known to be the first limiting amino acid, followed by threonine and methionine.   It is presumed that this may be true in horses as well.   In a study looking at pregnant mares, their subsequent foals and the mare’s themselves during lactation, researchers posed the question if plasma amino acid concentrations would differ after eating.   Theoretically, plasma amino acids which increase the least after eating immediately following a fast indicates the limiting amino acids.  In the weanlings, the amino acids which increased the least were methionine and lysine, for lactating mares it was methionine and for pregnant mares on this particular diet the amino acid which increased the least was leucine, one of the branched chain amino acids.  This study supports the idea that methionine may be the second limiting amino acid for nursing mares and weanlings, but leucine may also need to be considered.  However, this study did not provide information on how much of these amino acids may actually be needed in the diet, but stresses the need for additional studies.

    The final study we will look at did try and examine the question of methionine needs in growing horses.   In a study which looked at the growth rate and plasma metabolites of weanling horses fed differing amounts of methionine, growth rate did not change with addition of methionine. However, weanlings were only fed the diet for 56 d which way not have been long enough to observe differences.    Addition of methionine did result in a decrease in plasma urea nitrogen.  But what exactly does that mean?   Remember that any extra amino acids must be catabolized and the amine group is removed as urea. The urea is synthesized in the liver, but excreted by the kidney.  Urea circulates though the blood prior to its removal.  An increase in plasma urea N indicates an increase in amino acid catabolism, which takes place if protein synthesis is limited by the availability of amino acids.  If we assume that an increase in methionine in the diet allowed more protein synthesis to occur, this would result in more N retention, and less amino acid catabolism.  In this study, the authors did not observe a linear decrease in plasma urea nitrogen as  methionine was increased beyond 0 .2% of the concentrate. In this example, the weanlings were fed at a rate of 1.25% of their body weight in concentrate, or about 8.4 g of methionine.  You may have noticed that many feed companies now include the levels of methionine in their product.  Using this study as an indicator of methionine requirements, at least for weanling horses would indicate that methionine should at least be at the level of .2% of the concentrate if fed in comparable amounts. If less concentrate is fed, than the concentration of methionine should be higher.

    To summarize what we can take from these three studies, we have reaffirmed that mature idle horses don’t really need high protein hays. While their protein may be more digestible, those amino acids remain largely wasted.  For horses with higher protein needs, it may be time for us to turn our attention to more than just protein quantity, but quality as well.  Hopefully soon we will have better knowledge on exact amino acid requirements, but at least we are now somewhat closer to knowing about methionine!

Items 1 to 10 of 59 total

Page:
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6