Tag Archives: Equine
Written By Kris HineyWith proper care, today’s horse owner can expect to have their equine companion for 20 to 30 years. Advances in veterinary care, parasite management and nutrition, allow us to sustain horses much longer than what would be observed in the wild. With proper attention to their nutritional needs, even the body weight and the condition of the horse can be maintained in a very good state. So what types of changes in the diet of the older horse should you address?First of all, when should you begin treating your horse as an “old horse”? Typically horses older than 20 years are considered to be aged, but this may vary from horse to horse. Visual signs of aging include a loss of body weight, a loss of muscle mass over the top line of the horse, graying around the eyes and muzzle, and stiffening of the joints.However, one of the most fundamental changes in the older horse is an alteration in its teeth and its ability to masticate its feed properly. Horses' permanent teeth begin quite long, (4-5 inches), with only a portion of the crown visible in the oral cavity. The teeth continue to erupt throughout the horse’s life as the crown of the tooth is wore down by grinding against the opposing teeth and the forage the horse consumes. As a horse ages, continual grinding of its feed wears down the surface of the horse’s tooth. Eventually as this process of tooth eruption and wearing away of the crown continues, an old horse will essentially “run out” of teeth. Examination of the molars and premolars of elderly horses may show a very short molar in comparison to a younger horse. The root of the tooth may become less stable, resulting in a loss of teeth. Teeth remaining in the jaw which are unopposed grow into the remaining space and can press directly against the gums.An older horse's mouth may not only be less functional but quite painful as well. Attention by a veterinarian or equine dentist is imperative to insure that any such problems are addressed. However, no veterinarian or dentist will be able replace a horse's lost teeth. In that case, the diet of the horse must be altered.Proper chewing is imperative to allow a horse to digest its feed. Because the base of the horse’s diet is forage, mastication is necessary to disrupt the tough cell wall of the plants. Without proper chewing, enzymatic digestion of the feed in the small intestine will also be limited. With the horse unable to digest its feed to the same extent, the amount of feed that used to be able to support a horses’ energy needs is no longer enough — much of the energy content of the feed is actually lost in the feces. The type of feed offered to the horse must now be much more digestible with less work by the horse!Most major feed companies manufacture diets designed for aged horses. These feeds are typically pelleted or extruded, which eliminates the need of the horse to perform much chewing. Horse owners can make their senior citizens' job even easier by wetting the feed to create a meal of mash-like consistency. Often these feeds can represent the sole component of the horse’s diet as they contain forage/ roughage, but in a form that is ground or finely chopped. They also contain feedstuffs that are highly digestible and calorically dense.Fats provide a great deal of energy (2.25 x more so than carbohydrates), are highly digestible and are palatable to the horse. You may also see different types of fiber sources added that are also easily digestible such as beet pulp, citrus pulp, rice bran, etc. These fiber sources are rapidly fermented by the horse and are safer to feed than providing your horse a large amount of starches and sugars. Molasses added to feed does serve the purpose of increasing palatability and, thus, intake in horses. If your older horse has a history of insulin resistance or metabolic syndrome, avoid feeds which contain a substantial amount of molasses. It may be necessary to try several feeds to determine which your horse finds most acceptable and will readily eat.Hay cubes can also provide a form of forage that an older horse can readily consume. Again, if your horse has trouble chewing the hay cubes, they can be moistened for easier consumption. If you are feeding horses this way in the winter, be sure to not offer the horse more feed than he can consume before it freezes. In addition, broken teeth may be more sensitive to cold and make him further reluctant to consume his feed!Beyond an older horse’s lack of teeth, there may be some evidence that they simply do not digest feed in their intestines as efficiently as younger horses. It is even more important that these horses receive a balanced diet that can meet their energy, amino acid, mineral and vitamin requirements. However, don’t go overboard and begin to randomly supplement your horse indiscriminately.If he is housed with other horses, he may lose status in the social hierarchy as he ages. This could greatly affect his access to feed and should be carefully monitored.Older horses frequently suffer from arthritis as well. Certainly, if your horse is uncomfortable or in pain he will be less likely to have a good appetite. While long term administration of NSAIDs may help to eliminate your horse’s pain, it may also cause an increased risk of ulcer formation. This will only further discourage the horse from eating. Alternatively, omega-3 fatty acids have been reported to decrease lameness scores and inflammation. Thus, feeding a source of n-3 fatty acids may keep your older horse more pain free with less gastric disturbances.Finally older horses may be at an increased risk of disease transmission due to an age-related decrease in their immune system. It is important to provide an environment that is as stress free as possible for your horse to maintain good health.Following these tips, as well as regular vaccinations and deworming schedules will help your horse have a good chance of reaching its 30s!
Written By Dr. Kris HineyThe fall season is here and with it often comes the time for weaning our foals. Many successful weaning strategies exist but it is important for the manager to choose the optimal one for their facilities and management style. These decisions are important and can affect the growth, well being and even the future behavior of your foal.When is it appropriate to wean?Foals can be weaned at any age provided their proper nutrition and socialization skills are ensured. Foals whose dam’s may die at birth are obviously “weaned” from their dam at an extremely young age. While it is preferable to find a willing nurse mare, and it is even possible to induce lactation in a non-pregnant mare, many owners choose to put the foal on a liquid diet of formula designed to match the mare’s own milk. Specialized milk replacer, goat’s milk and supplemented cow’s milk can all be used successfully. Prior to doing so, it is important to ensure that the foal has received adequate amounts of high quality colostrum, as the proteins found in the milk replacer may block the later absorption of immunoglobins from colostrum. Colostrum content quickly decreases in post-partum mares and should have been harvested within the first three hours post parturition of the donor mare.Orphaned foals must be fed frequently , initially from a bottle, but can then be taught to drink from a pail, similar to calves. Initially the foal should be fed at 5-10% of its body weight in the first day, and then increase to 20-25% of its body weight by day 10. Solid feeds can be introduced early, as the foal would typically begin to ingest feed in imitation of its dam after only one week of being born. Milk replacer pellets are available, and can help supplement the foals’ initial liquid diet. Foals can be weaned from this liquid diet by 10-12 weeks of age. Most importantly, some sort of companion should be found for the foal. Often orphan foals develop undesirable behaviors as they have no guidance from a mature horse as to what constitutes appropriate social behavior. Typically, orphaned foals view humans as their peers, which may result in some rather inappropriate rough play!With the exception of extremely early loss of the dam for a variety of reasons (death, injury, sales, etc.) most managers choose to wean foals between three and six months of age. In the feral state, foals typically are self weaned by 35 weeks of age or between eight and nine months. At five months all foals spend 50-70% of their day consuming solid feed, compared to about 2% of the day suckling. Mare’s milk production also begins to drop off by three months of age, at which time foals are consuming a high percentage of natural feeds through grazing, hay or concentrates. It is advantageous to introduce the foal to the feeds it will be consuming post-weaning to ensure an easier and more stress-free transition. This will also help prevent fluctuations in growth rates that may place the foal at risk for developing developmental disorders.After insuring that the proper diet is being fed (see previously related articles concerning protein, energy and minerals for growth), the management system used is important to consider. Foals weaned in isolation (such as confined in a box stall) show more incidences of stereotypies (such as weaving, cribbing and wood chewing) and are more vigilant (less time standing relaxed) than foals weaned in pairs. Foals weaned in stalls also show more abnormal behaviors such as stall licking, kicking, rearing and pawing than weanlings weaned in a paddock. Even horses stabled for the first time as two year olds exhibited much less aberrant behavior and were more relaxed when stalled in pairs versus singularly.Therefore the ideal management system would wean the foals with a counter-part, rather than in isolation. For example, at our facility we wean the foals by removing the dams, with foals remaining in the same pasture and with the same herd mates with which they have been raised. This results in very little stress (at least as exhibited by vocalizations and seeking of their dam) which is frequently resolved within two days post weaning. Even in this system we wean in pairs, whether or not this actually relieves stress for the weanling. If raising only one foal, it is advisable to seek out an older quiet pasture mate, or even to find another youngster to raise with it. Many horse owners find themselves in a similar situation and may be willing to board another weanling or send theirs as a companion.Alternative strategies include gradual weaning, in which the mare and foal are separated, but are allowed all behaviors except nursing. Typically this is done over a fence that the foal simply cannot nurse through. After one week, the mare is removed completely. Foals weaned in this manner, exhibit less stress and have lower levels of cortisol (a stress hormone) than foals which are weaned abruptly. However, these foals are no different than abruptly-weaned foals after two weeks. The advantages to this system may simply be a lessened possibility for injury or disease.Weaning stress may also make the foal more susceptible to diseases. Because of this, be sure that the foal is in good health prior to weaning (we typically have vaccinated the foal and ensured a high immune status prior to weaning) and there are no undo stressors. For instance, plan the time of weaning for when the climate is not too adverse (either too hot or too cold/wet). Because the mare and foal may show high stress and try to re-unite, check that the facilities used for weaning are extremely safe. Expect that maiden or younger mares may exhibit a longer period of time in which they still call for or seek out their foals. Halter breaking is not advisable right at the time of weaning either, as the foal is already stressed and more reactive. Ideally foals are handled from birth, which can lessen the stress of procedures often introduced at this time (vaccinations, deworming, farrier care, etc).Care of the mare is simple, with usually a decrease in ration quality or quantity from that received as a lactating mare. Although her udder will fill initially, it is important to not milk the mare, as this will only further stimulate lactation. The udder should become soft within a week of weaning. She can then be returned to her pre-foal life, whether that is as a riding horse, a gestating mare, or simply a mare of leisure.
By thinking through the weaning system and the safety and nutritional needs of both mare and foal, the stress of “growing up” for the foal can be greatly minimized.
Written By Dr. Kris HineyLast month we discussed the usefulness of fat in the equine diet, as well as some examples of typical feeds which contain fats. Fats are an easily digestible source of calories which can readily supply the extra energy that performance horses may need. Fat may lower the heat load on the horse compared to traditional diets, which may aid in performance in hot climates. Finally, fat may even help calm the horse compared to when they are fed high starch diets. But is there any other reason to feed fats that may help you get to the winner’s circle?Fat MetabolismWhen horses are fed fat in the diet, their body responds by increasing the number of enzymes that are involved with lipid metabolism. These include the enzymes needed to remove fat from the bloodstream and enter muscle or adipose tissue, and those that ultimately oxidize the fatty acids. Feeding fat to horses results in a lowering of plasma triglycerides which is believed to be caused by a decrease in synthesis of triglycerides in the liver. The horse becomes more efficient at utilizing dietary fats for energy, rather than needing to use carbohydrate or protein. This adaptation has repeatedly been shown to take at least three weeks after the change in diet. Complete adaptation may take as long as 2-3 months. Therefore, if switching your feeding regimen, don’t expect to see instantaneous results.Exercise and Fuel SourcesWhen fatty acids are oxidized in the body for fuel, their final metabolic pathway involves the Tricarboxylic cycle (TCA)* or Kreb’s cycle. This cycle is dependent on oxygen (through its connection to the electron transport chain) in order for it to work. The TCA cycle supplies the bulk of Adenosine Triphosphate (ATP)** for horses when they are working aerobically, or at lower intensities. Technically, aerobic work is at a low enough intensity that the requirement of ATP can be met by the slower metabolic pathway of the TCA cycle. At low intensities of exercise, fat typically supplies up to 50-60% of the calories needed. All dietary energy sources – fats, carbohydrates and protein – can be utilized in aerobic metabolism, provided there is sufficient intake of oxygen. That means that the horse’s heart and lungs can keep up in the race to deliver oxygen to the tissues. However, when the horse’s muscles are contracting faster or harder than the ability of the cardiovascular system to keep pace, they then enter into anaerobic metabolism. The horse must then switch to a different supply of fuel, primarily carbohydrate metabolism. They are simply working too hard for the aerobic system to keep up with the demands of the muscles for ATP. Therefore, horses undergoing intense exercise, or sprinting type of activities, must rely on their carbohydrate stores for energy. These include blood glucose, liver and muscle glycogen, and the body’s ability to perform gluconeogenesis (make glucose from other sources).Can Fat Save Glucose?It is presumed that due to the adaptation of the horse to become more efficient at fat metabolism, they are less reliant on their carbohydrate stores (blood glucose, muscle and liver glycogen) to supply their energy needs. This should allow the horse to work longer before turning to carbohydrate metabolism. This may be advantageous for two reasons. One is that carbohydrate stores in the body are much more limited in comparison to lipid stores, and two, usage of carbohydrate through anaerobic metabolism can result in the production of lactic acid. This may contribute to the onset of fatigue, due to depletion of energy sources or the accumulation of lactic acid. Therefore, fat fed horses may have some advantage in their resistance to fatigue.Most studies of horses fed high fat diets have reported an increase in resting muscle glycogen stores. However, there have been a few reports which have shown an opposite effect of lowered muscle glycogen. In these studies, the horses were either untrained or receiving low intensity exercise. In studies which exhibit an increase in resting muscle glycogen, the horses received more intensive training, including sprinting exercise. This may be the key in seeing a response to the fat added diet. In addition, the amount of fiber and starch in the rest of the diets differed between studies, which also clouds interpretation. If horses do have higher glycogen stores at rest, it is unclear if this results in an increase in glycogen utilization during exercise. Some researchers found an increase in glycogen utilization while, again, others have found no change in glycogen metabolism during race simulations or long term sub-maximal exercise. But would an increase in glycogen utilization improve performance? Again results are mixed. Horses fed 12% fat for four weeks improved their run time to fatigue in a high intensity exercise bout on a treadmill. Others have found increased performance in sprinting exercise and in a simulated cutting event, while some have found no clear advantage to feeding fat in improved performance.Is Anything Consistent?In studies looking at blood metabolites in exercising horses fed a fat added diet, some consistent results have been seen. Feeding fat does decrease the exercise related drop in blood glucose. This is seen simultaneously with an increase in serum triglycerides and free fatty acids. Presumably these horses have indeed shifted toward a more efficient utilization of fatty acids during exercise, sparing their glucose stores. This seems to be supported by data which shows that horses on fat supplemented diets have a higher blood pH during exercise versus non-supplemented controls. The above effects are seen at lower intensities of exercise. When the horse increases its ATP demand, they will need to draw more from anaerobic metabolism and must shift to carbohydrate usage.So with all of these conflicting results, what should you believe? It is clear that feeding performance horses fat rather than carbohydrates is a much healthier alternative. High carbohydrate diets carry with them the risk of laminitis, colic, ulcers and insulin resistance. As of now, no negative effects of feeding fats to horses have been found. The potential benefits are many, including a potentially calmer horse, a decrease in reliance on blood glucose (at least at lower intensities), and a possibility of increased performance in anaerobic activities. With little to lose, and benefits to gain, it is no wonder fat added diets are so popular in the equine industry.Next month – The usage of fat added diets in metabolic diseases.* TCA – Tricarboxylic cycle, also known as Citric acid Cycle, has been described as the “central metabolic hub of the cell”. A sequence of reactions taking place in mitochondria where acetyl units attached to CoA are degraded to carbon dioxide and the electrons produced transferred to the coenzymes NAD⁺ and FAD.**ATP – adenosine triphosphate, an adenine nucleotide used as the energy currency in metabolism. The free energy released when ATP is hydrolyzed is used to drive reactions in cells.
Written By Dr. Kris Hiney
Last month we learned that meeting a mature idle horse’s protein requirements are surprisingly easy. If a horse is provided with good quality hay at 2% of its body weight it can easily consume enough protein even without eating concentrate. However, if forage quality is low, adding a supplemental designed to provide essential amino acids can easily make up the difference.
But my horse works hard!
But what about if your horse has more of a job to do than just stand in his pasture and eat? Many people automatically reach for a higher protein feed once their horse goes to work, but is that really the right thing to do? Of course protein requirements of a working horse do go up due to the increased tissue turnover and repair associated with exercise. Further, horses also lose nitrogen through sweating and increase muscle mass with training. However, the increase in protein required pales in comparison to the increase in calories needed. High protein diets increase the need for horses to excrete urea (the form in which excess nitrogen is removed from the body) and may alter their acid base balance. While horses seem to be able to handle the increased need to remove nitrogen from higher protein diets quite easily, it will result in more urine excretion. Thus more ammonia may build up in poorly ventilated buildings and bedding costs will go up. In fact, it may be beneficial to feed a lower total protein amount to the horse while providing key amino acids. In one study, horses fed a lower protein diet but supplemented with lysine and threonine had higher blood pH values after exercising compared to horses on a higher protein diet (Graham-Theirs et al., 2001). When horses exercise intensely they produce lactic acid. Lactic acid drops the pH in the blood and can contribute to the onset of fatigue. Therefore this lowered protein diet may protect against a drop in blood pH and therefore allow the horses to exercise longer or recover faster. However it should be noted that the lower protein group was also supplemented with fat as well, clouding interpretation of results.
So how much do they really need?
Table 3 shows the total amounts of protein needed, while Table 4 again expresses this on a % protein basis. You can see that most performance horses will do quite well if you select a feed between 10-12% crude protein. Remember that when selecting a feed, you must consider your forage source first! For example, if your performance horse was eating a primarily alfalfa hay with a value of 16% crude protein, his protein needs would already be met! Selecting a concentrate then would primarily serve to supply any additional energy needs the horse may have.
Table 3. Crude protein requirements for work (g of CP/d).
Wt of horse (lb)
Table 4. Percent total protein required in the diet on an as-fed basis depending on the total consumption of the horse per day.
% of Bwt consumed
Let’s do math!
Now let’s put this together in a practical problem. We will feed an 1100 lb horse 2% of his body weight in grass hay. Our grass hay has 9% crude protein value on a DM basis. We weigh out 22 lbs of hay for our horse per day but we weigh it on an as-fed basis (meaning what it weighs on a scale that day).
First we will convert our weight of hay to the weight of our hay on a dry matter basis. We will assume the hay is 85% dry matter.
22 lbs x .85(% dry matter) = 18.7 lbs of hay on a dry matter basis
Then we will convert our lbs to kilograms.
18.7 lbs /2.24 = 8.3 kg of hay
Multiply that by our percentage of protein.
8.3 kg x .09 = 747 g of CP.
Let’s check this horse’s lysine requirements as well. Remember that the only value for amino acids required by the horse is for lysine. The current available knowledge suggests that horses need 4.3% of their protein to come from lysine. Typically grass hays are fairly low in lysine compared to legume hays. An average grass hay harvested at a mature stage is 0.38 % lysine. Again we multiply the amount of hay fed 8.3 kg x .0038 = 31.5 grams of lysine. Our maintenance horse only needs 32 grams of lysine. We therefore have met his requirement by feeding this hay.
Even if our 1100 lb horse is in moderate work we are short by only 7 grams of CP. This can easily be met by any additional concentrate or by simply eating more hay. However, if we move him up in work, we become much more deficient in protein as well as lysine. Let’s assume he is now in heavy work and deficient by 100 g of protein. We want to add 3 lbs of concentrate (which isn’t very much) to his diet.
3 lbs /2.24 = 1.3 kg of feed
We need our 1.3 kg to supply 100 g of CP. So our feed needs to be 100g/1300 g of feed = 7.7 % CP on a dry matter basis. On an as fed basis, this would be 9% CP. Almost every commercial feed will contain this level of crude protein. Hopefully we have now illustrated that there is no need to feed a high protein feed designed for growing horses or broodmares to our exercising horses.
In summary, protein requirements for maintenance horses or even those at work are fairly easy to meet by a normal horse diet. If feeding a poor quality hay, you may have to supplement your horse’s diet. If so, then choose a feed that contains legumes (like alfalfa meal) or a concentrate that contains a high quality protein like soybean meal. While no clear amino acid recommendations are available for working horses, there appears to be some benefits of feeding lower total quantity of protein while supplementing with key amino acids. This certainly does appear to be the future of equine research concerning protein nutrition.
Next month we will address the protein needs of the groups of horses which need the most attention: the growing horses and the broodmares.
Written By Dr. Kris Hiney
In the last two articles we discussed the importance of protein quality, not only in terms of site of digestion in the horse, but also the amino acid composition of that feed. Now we will try to simplify these concepts into selecting appropriate feeds for horses.
The first task in developing a feeding program for your horse is to identify what class of horse you have. (For a review revisit: Equine Energy Requirements and Energy Requirements for the Working Class) The horses with the lowest protein requirements relative to their body size are the mature horses not in work, or maintenance horses. This does not include geriatric horses which may have altered protein needs due to the lowered efficiency of their digestive system. We also must assume that the horse is receiving enough calories in the diet. A horse fed a diet sufficient in protein, but low in calories will lose weight (makes sense right?) but a horse which has adequate calories but not enough protein can also lose weight. We also make some consideration for the activity level of the horse as well. Remember the difference in energy requirements between the couch potato Quarter Horse and the active Thoroughbred mare (Equine Energy Requirements)? Well a similar relationship exists with protein requirements. Essentially the more active horse would have more lean tissue/muscle to support than the lazy horse. Table 1 lists the actual protein requirements for a maintenance horse depending on activity level and their body weight. Remember that this does assume a quality protein source. Lower quality protein (less digestible or poor amino acid profile) can adjust these figures upwards.
Table 1. Crude Protein requirements for maintenance (grams of CP/d) based on average activity level.
Wt of horse (lb)
What percent protein do you need?
But let’s put these numbers into something more people are familiar with, percent of the diet. Table 2 provides the percent protein of the total diet a horse would need to consume to meet their protein requirements. Looking at Table 2 shows how easy it is to meet a maintenance horse’s protein requirement. You can also see that as total consumption goes up, the percent of the protein needed in the diet goes down. Conversely, if you fed less you would need to increase the percent protein in the diet. Horses will usually consume between 1.5 and 2.8% of their body weight per day on a dry matter basis. Typically you will see horses lower their consumption of less palatable hay which often equals poor quality. However, this can largely be based on the individual, as some horses compensate by lowered feed quality by increasing intake (Edouard et al., 2008). It turns out that horses are much more variable in their voluntary intake than other domestic species are! Just like a horse to always want to be unpredictable. If you notice your horse picking through its hay and leaving a good proportion of the hay untouched it may be wise to select a supplement designed to provide amino acids but not to greatly increase the calorie consumption by the horse. Alternatively it may be time to find a new hay supplier (see Selecting Forages).
Table 2a. Percent total protein required in the diet on a dry matter basis depending on the total consumption of the horse per day.
% of Bwt consumed
Table 2b. Percent total protein required in the diet expressed on an as fed basis assuming an average dry matter content of 85%. Note: this can change with the feed fed and is only representative of harvested feeds, not pasture or grasses.
% of Bwt consumed
Protein content of common horse feeds
Now let’s look at some typical protein values for feeds. To be sure of your own feed ideally have your forage tested as well as examine your feed tag. Corn ranges between 8-9 % CP on a DM basis, oats 12-13%, soybean meal – 43-49%, grass hays – 10-18%, and legumes between 18-25%. With the range of protein content in forages, one can see how important it is to have knowledge of your nutrient content prior to selecting your concentrate. Even with these ranges, most maintenance horses will easily meet their protein requirements by forage alone. If you look at the range of percent protein needed by the maintenance horse in their total diet, it compares quite well with grass hays. If you are feeding your horse and he is maintaining weight, he should easily be meeting his protein requirements at the same time. Remember, we assume the horse is receiving good quality hay. If you are worried about the horse meeting its amino acid needs, many feed companies make supplements specifically designed to be fed with a strictly forage diet, rather than greatly increasing the concentrate intake. For example, many feed companies offer protein supplements in the range of 30-35% crude protein. These are designed to be fed at a minimal rate (only 1-2 lbs per day) in order to simply balance out any deficiencies from an all forage diet. Clearly not all horses need the extra calories that come from feeding higher levels of concentrates. This provides a convenient, easy way to ensure that your horse’s nutritional needs are being met.
Next month we continue with protein nutrition in the exercising horse.
Edouard et al.2008. Animal:An international journal of animal biosciences. 102:10:1526-1533.
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