Ask the vet: Nutrition

Join AAEP's "Ask the Vet" forum during July to pose your questions on the topic of equine nutrition to our AAEP expert, Dr. Lydia Gray from SmartPak Equine.

Question: In the hot summer months when my horses are sweating a lot, which electrolyte supplement would you recommend feeding? There are so many on the market and so many articles about which ones to feed and which ones to avoid.
I agree, there are a lot of choices out there when it comes to electrolytes! And since replacing the vital nutrients lost in sweat as well as encouraging horses to drink and rehydrate themselves are both critical to your horses’ health, so let’s see if we can help you sort things out. 

Some things to consider when choosing an electrolyte are palatability (i.e. tastiness), the presence of extra or unnecessary ingredients (like sugar), and how closely the supplement mimics the minerals horses lose in their sweat. The ideal equine electrolyte, therefore would be one that horses eat readily, that contains little or no added sugar, and that is formulated to replace what is actually lost from the horse due to sweating. Numerous studies in this area have shown that the major ions found in horse sweat are chloride (Cl), sodium (Na), and potassium (K), in that order, with a little bit of calcium (Ca), so look for a supplement with primarily these macrominerals. Here is a link to a fact sheet with more detail about sweating in horses and electrolyte supplementation to replenish losses: 
Question: I would like to know, when feeding crimped oats, what vitamin/mineral supplement would be a good choice. My horse is a pleasure AQHA gelding, not worked but 2 to 3 times a week.
If your horse was getting a full serving of a fortified grain I would tell you that a vitamin/mineral supplement isn't necessary, but since your horse is getting just crimped oats for extra calories, you’re smart for looking into a vitamin/mineral supplement to complement his diet. I’m going to assume that he is also getting an appropriate amount of quality hay. 

When looking for a multivitamin, remember that not every horse’s nutrient needs are equal. Your horse’s workload will influence his vitamin and mineral requirements, so look for one that differentiates between different workloads. Also consider looking for a multivitamin designed for his life stage. For example, senior horses may benefit from additional vitamins that also serve as antioxidants such as vitamins E and C. If your horse is older, look for a multivitamin formulated with the senior in mind. Lastly, palatability is important as the supplement won’t do him any good if he doesn't eat it. Try and find a pelleted option, as most horses prefer them to powdered supplements.
Question: I have three older horses(15, 20, and 25) that are fed hay twice daily, and get pasture turnout two hours in the afternoon/evening. The pasture is now dry and getting sparse. Their weight remains good as I have always fed 1/2 grass hay and 1/2 oat hay. This year my local feed store has run out of oat hay several times and they recommended feeding wheat hay. I tried it and the horses loved it! Are there any problems associated with feeding non-bearded wheat hay? Any benefits over oat hay?
That’s great that your horses all like the wheat hay, as some don’t care for it. Where I’m located, neither oat nor wheat hay are very common forages for horses; we’re more familiar with oat and wheat straw for bedding. If the wheat hay is beardless, it’s been tested for nitrates, which can be high in both these crops, and you’re feeding a ration balancer to provide protein, vitamins and minerals (especially calcium) then gradually introducing your horses to this new forage should not be an issue. 

If you’re concerned about this significant switch in hay types, consider adding a digestive supplement with ingredients like yeast, probiotics, prebiotics and enzymes to assist in the transition, much as you would when introducing horses to pasture in the spring. Remember that changes in hay can increase a horse’s risk for colic by ten times (while changes in grain can increase the risk five times).
Question: I have a 26-year-old Tennessee Walking horse that has recently started losing some weight around his flanks. He is free of parasites (this was checked last month) and an equine dentist pronounced his teeth in good condition. Good pasture is available to him 24/7 and he is also fed about 4lbs of grass hay daily at this time though he prefers to graze in his pasture. He receives no grain. I started him on Purina Senior about 10 days ago to supplement his nutrition needs and am feeding him twice per day (3.5 lbs per feeding). I have been told by my local animal feed store that I could put more weight on him by using Purina Strategy or Purina Ultimum. He is not worked and only on a maintenance feeding plan. He is otherwise alert and seems happy with his other Tennessee Walking horse companion. Could you please advise me on a feeding plan?
Congratulations for getting this far with your guy! Now it may be time to think of him as a senior horse with senior needs. I’m really glad to hear that you've had his mouth inspected and all seems to be fine there. You still need to make sure that he can bite off, chew and swallow pasture grass though and hasn't begun quidding. If you suspect that may be the case, he might not be able to masticate long stem hay either in which case it’s time to transition to chopped hay, hay cubes or hay pellets.

Next, AAEP has just published Parasite Control Guidelines that I would encourage you to read, with one of the first things you’ll learn being that no horse is truly “free” of parasites. He may be a low shedder, or the parasites may not be laying eggs right now, but I’ll guarantee you that your horse has worms so please don’t neglect giving him dewormer at least once or twice a year! The older horse begins to become less efficient in many organ systems, including the immune system, so an appropriate parasite control program (and vaccination program) becomes even more important as he ages.

Another organ system that doesn't work as well as cells and tissues get older is the digestive system. Since he’s now less able to extract nutrition from the same food he’s always eaten, starting him on Purina Equine Senior was a great idea! This commercial “hay and grain in a bag” is specifically made for the older horse, with higher protein levels to keep their topline and other muscles from wasting and easier-to-digest ingredients than traditional concentrate. Since it is like both hay and grain combined--with feeding rates as high as 12, 15, or even 18 pounds per day--don’t be afraid to add a third meal or to give him more each time. Of course, if you switch to a true concentrate like Strategy or Ultium, you would feed much less. So there’s a trade-off between feeding large amounts of a highly digestible feed made for senior horses or smaller amounts of a higher calorie feed made for hardworking or hard-keeping horse. You may want to (gradually) try both approaches and see which does a better job of keeping weight on your individual animal.

There are lots of other ways to put weight on horses and keep it there, and unfortunately you have to do a little bit of experimenting with your own horse to see what works best for him. Some horses really blossom when the diet is supplemented with additional protein or amino acid, others respond to extra fat, while still others gobble down beet pulp, a high fiber feedstuff, which is fermented by the beneficial bacteria in the hindgut into fatty acids or energy. I recommend trying one thing at a time and seeing how your guy does, while at the same time identifying and removing sources of stress or unnecessary calorie loss, such as stomping flies in the summer, shivering in the winter, or illnesses and injuries. I’m also a big proponent of keeping horses in consistent light work as long as possible, soundness permitting, as even walking promotes muscle development.

And of course, stay in touch with your veterinarian, who may want to bump up the annual visit to twice yearly, since problems with immunity, digestion, teeth, hooves and other parts happen much faster once horses enter their golden years. Good luck and enjoy your horses for a long time to come!
Question: I have a 10-year-old Warmblood/Thoroughbred that I got last fall. At that time, he was on a high fat high fiber diet. His weight has decreased so we have switched him to a Purina feed, which is suppose to give him all the calories he needs. He has been dewormed recently and does not spill his feed when he eats. I believe his teeth are good. He is currently on grass and always has hay. He shares pasture with two others and is use to being in a herd. I was thinking about checking for ulcers? Any ideas?
If I were your veterinarian trying to help you figure out why your horse lost weight and how he might gain it back, I would want to know a couple more things. For example, what was his body condition score (BCS) last fall when you acquired him and what is it now? Each BCS is about 50 pounds (slightly more for a larger horse like a Warmblood or Draft) so if he was a 5 and is now a 4, he lost 50-75 pounds. If he is a 3 now, he may have lost more like 100-150 pounds.

Next, where do you live and where did the horse come from? If in a northern climate, do you think he either did not acclimate to the move or just in general has a hard time keeping warm in cold weather and burns a lot of calories to do so? I had an OTTB that would consistently lose weight in the SUMMER because he didn’t tolerate the heat or bugs well and just stood around stomping instead of eating. That said, make sure you understand your new horse’s personality and metabolism when it comes to seasonal weather changes.

What do you do with this horse? If he came from a pasture ornament situation into full training and is now expected to compete in dressage, eventing or as a hunter/jumper, then his caloric intake needs to increase accordingly. 

You mention that he is used to being in a herd and now lives with two other horses. How did the establishment of pecking order go? Do you know where he is in herd hierarchy? Sometimes horses get pushed off their hay pile prematurely and spend the bulk of their eating time getting moved around, which uses up calories instead of taking them in. The Warmblood I have now wears a grazing muzzle at all times because he can inhale all eight piles of hay in “his” seven-horse paddock faster than you can say “easy keeper.”

Since you also describe the grain that he eats (Purina TriMAX, available in Canada), I’m assuming you bring your horses into stalls for meals or in some way separate them so they can eat their fair share in peace? Speaking of “fair share,” Purina recommends feeding a range of 0.5 to 0.75kg grain per 100kg body weight. If we assume your horse weighs 500kg (1100lb) then he should be getting 2.5 to 3.75kg each day (5.5 to 8.25lb), aiming for the lower end of the range to meet his minimum vitamin, mineral, and protein needs and the higher end of the range to provide extra calories for heavy work or weight gain. Remember the rule of thumb: no more than 0.5% of a horse’s body weight per grain meal, which for a 500kg (1100lb) horse is 2.5kg (5.5lb). To use this grain as it is intended then, you should be giving your horse 1.875kg (a little over 4lb) in the morning and in the evening.

Since that’s a lot of grain and feeding large amounts of grain has been linked to gastric ulcers, you may want to provide calories via another route, such as beet pulp, alfalfa cubes, a fat supplement or other option. Each horse responds differently to these various methods of increasing the energy in the diet so I recommend trying one at a time, for about a month, before moving on to the next. The clinical signs of ulcers, their diagnosis, treatment and prevention have been covered in great detail elsewhere, so I’ll let you research those facts on your own!

Finally, if you have not had a qualified person actually examine his mouth and inspect his teeth since you purchased him (and performance horses usually get looked at twice a year) then it’s time. Also, I strongly urge you to read AAEP’s guidelines on parasite control, to make sure your program is as up-to-date as possible. If careful consideration of what changed in his life since you purchased him and attention to the details of his diet don’t improve things, then it may be time to have your vet out again to examine him and try to get to the bottom of his weight woes.
Question: I rescued three starved horses, two 12-year-old Percheron geldings and a 23-year-old Quarter horse mare. My veterinarian told me to put them on some high fat/high fiber and I was also told senior would be the best as its HF-HF, and easily digestible. What would you recommend?
I’m impressed that you rescued three horses at one time! You’ve certainly got your hands full! Fortunately for you, and for them, my background is in horse rescue and I swore by the research that Dr. Carolyn Stull and her team did at the University of California-Davis. She found that starved horses were not unlike starved people (think POWs) in being susceptible to refeeding syndrome, which can be fatal. 

This syndrome happens when a person or animal goes without food for a long time, begins to breakdown their own body for nutrition, then is “rescued” and given food high in energy/calories, which then leads to electrolyte disturbances and even death. She found that small, frequent meals of alfalfa hay were the best way to bring starved horses back to health, as oat hay was too high in fiber and too low in other nutrients but grain was too concentrated a source of calories. Here is the research if you would like to share it with your veterinarian so you can develop a safe feeding plan:

My advice is don’t be in a hurry to fatten them up or to put their preventive care programs in order (vaccines, parasites, teeth, hooves). All of these procedures create stress and some, like immunizing, rely on the horse’s body to mount an appropriate response. If they’re truly a body condition score of 1, immunizations will likely slow down their recovery while conferring no protection. So give them time to eat and heal from the inside out; there will be plenty of time later to start providing good veterinary medical care!
Question: I own a 13-year-old Morab mare that is out on pasture. I have not been riding much lately. She has her deworming, vaccinations, feet and teeth up to date. Should I give her any free choice mineral, and if so, what would you recommend? The horses do have access to a cobalt salt lick.
There are a couple of key pieces of information missing from your question in order for me to give you the best advice, such as what part of the country you live in, how much and what quality of pasture she has access to, and if she is a an easy keeper or at an ideal weight (she could be a hard keeper but guessing from her breeds that is less likely). Depending on the answers to these questions, your horse “may” be getting a complete and balanced diet just from the pasture, but most horses don’t, as—you got it—minerals can sometimes be lacking or in the wrong ratio in some areas. 

I’m not a big fan of licks for horses, whether they’re white salt licks, red trace mineral licks or blue cobalt licks. These blocks were made for the rougher tongues of cattle and while some horses don’t mind licking them, others scrape them with their teeth or don’t bother with them at all. So loose minerals as you suggest would be a better choice, but rather than asking her to select what she needs or doesn't need (horses don’t have a craving for anything but sodium) why not top-dress salt or minerals onto something she likes, like a handful of oats, hay pellets or beet pulp? By separating the horses just once a day to supply their individual minerals, you’ll be ensuring that each horse gets his or her daily serving of essential nutrients.
Question: For a few years, my 18-year-old Appaloosa gelding has been given Equinyl Combo once a day. He has had no serious joint issues, but we want to maintain joint health. A veterinarian recently recommended Cosequin ASU instead. What is your opinion on the efficacy of each? One concern is that Equinyl is partially continued release, and Cosequin is not.
Kudos to you for staying on top of your horse’s joint health! Fortunately, more and more research is being published about the effect of oral supplements on the health of equine joints. ASU or Avocado Soybean Unsaponifiables is one example. In 2007, researchers at Colorado State University gave six grams of ASU (about three times as much as is in Cosequin ASU) to half of the horses in their study and a placebo to the other half. While there was no difference in pain or lameness between the two groups, the horses that received ASU showed a significant reduction in severity of articular cartilage erosion and synovial hemorrhage and a significant increase in glycosaminoglycan synthesis. That is, ASU had a disease-modifying effect, which is probably what your veterinarian is basing his recommendation on.

When it comes to choosing supplements there are many factors to consider, with research being one of them. You also have to take into account levels of key ingredients, cost, palatability and probably the biggest factor: how does my horse feel and move while on this product? For reasons I cannot explain, some horses seem to do better on a certain brand or with certain ingredients while other horses respond to a different brand or different ingredients. Since you and your vet know your horse best, I’ll step back and let you guys choose the product that is in his best interest!
Question: What are your thoughts on feeding naked oats? The nutrition value in protein and amino acids, fat, easily digested starch and in bonus avenanthramides is certainly the number one grain. What do you think?
I’ll admit, I had to look up “avenanthramides” to learn that they are a type of oat phytoalexin that exist predominantly in the groats of oat seeds and have antioxidant and anti-inflammatory properties. Now I finally know why oatmeal baths and shampoos can be so soothing to skin after a sunburn or poison ivy outbreak! And just so everyone is on the same page, hull-less or “naked oats” are high-fat (12-15%) varieties of oats that have been produced which are higher in energy than traditional oats.

In addition, hull-less oats typically contain more protein, including higher amounts of the limiting amino acids lysine and methionine. However, they also contain more phosphorous, so owners need to make sure the rest of the diet has appropriate levels of calcium to ensure the ratio between these two macrominerals is correct. So there are some pros to “naked oats” and some cons, and as long as you understand which type of oats you’re buying (with the higher price tag for hull-less oats this shouldn't be too hard) I say avenanthramides away!
Question: My horse appears to overproduce oil on his head. Could this have anything to do with his diet? His hair falls out in patches as though it is not being hosed down properly, but slowly grows back. Then the cycle begins again. This only happens when he is in full work. 
While there are some nutritional deficiencies and excesses that manifest as skin and hair conditions, I’m not sure this is the case in your situation. I recommend having your veterinarian out to examine your horse and perhaps take some skin and hair samples to get to the bottom of the problem. At the same time, you’ll want to share your horse’s complete history with your vet as well as what you’re feeding your horse, including when and how much. Hopefully, between the physical examination, biopsies or cultures, and evaluation of your horsekeeping and feeding, a diagnosis can be reached and appropriate treatment started so you can get back to enjoying riding!
Question: I have three Quarter horses and a Tennessee Walking horse. Their diet consists of a high quality forage (hay and pasture) with a mix of pelleted feed (low carb/no corn) and timothy pellets, supplemented with Gro strong vitamin and minerals, freshly ground flax seed, and biotin. They look great with a body condition score of 5 to 6. I have searched for a grass hay based feed that does not contain wheat middling or beet pulp. The commercial feed manufacturers do not consider wheat middling a grain since they sell 'grain free' feeds with wheat middling as the primary ingredient. What is the nutritional benefit of the wheat middling to the horse, or is a cheap filler?
Sounds like you’re doing a great job feeding your horses! To answer your wheat middlings question, I turned to AAFCO (Association of Animal Feed Control Officials), who defines it as a grain by-product that “consists of fine particles of wheat bran, wheat shorts, wheat germ, wheat flour, and some of the offal from the ‘tail of the mill.’ This product must be obtained in the usual process of commercial milling and must contain not more than 9.5% crude fiber.”

My other go-to source for equine nutrition, The Sixth Edition of Nutrient Requirements of Horses, says the inclusion of wheat GRAIN in horses diets is somewhat uncommon. However, wheat by-product feeds are often used in horse feeds, wheat middlings (midds) being one of the most common. Because most of the flour has been removed, wheat midds are higher in fiber and protein, but lower in energy than wheat grain. Wheat midds may contain more than one percent phosphorous so calcium supplementation is usually necessary when wheat midds constitute a significant portion of the diet. Due to their fine texture, wheat midds are not easily fed alone; however, they are commonly used in pelleted feeds.

Let me see if I can translate some of this nutrient-speak. First of all, don’t be alarmed by the use of the word “by-product.” I know the term scares some people off, but it doesn’t necessarily mean an ingredient is bad, all it means is that some ingredients, such as wheat midds, are not the main reason for processing wheat, which is primarily used to make flour for people. Because wheat midds are a by-product, their quality and nutrient composition can vary, but in general; this ingredient is high in protein, energy, starch, phosphorous, and potassium, with some trace minerals and vitamins to boot. So it does have nutritional value to the horse, and for this reason, as well as the fact that it’s fine texture helps bind pellets, you’ll see it in many commercial horse feeds.