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Equine Nutrition

  1. Can you advise me on hemp oil and hemp meal for my horses? (View Answer)

    The good news is that hemp (Cannabis sativa) is a nutritious agricultural crop, providing a complete essential amino acid profile, healthy fats, and generous servings of many vitamins and minerals. It’s also popular as bedding for horses because it’s less dusty and more absorbent than some other options. Hemp is a sustainable plant that’s been cultivated for use for thousands of years around the world.

    The bad news is that in the US, federal agencies and laws do not recognize the difference between hemp and its cousin, marijuana, which is the same genus and species but a different variety. So right now in this country, it’s not practical to rely on hemp-based products as a regular source of nutrition for horses since, at the federal level, large-scale hemp production is not permitted. Hemp import with permits is allowed – that’s why you see food, oil, and fiber products -- but the laws are still being sorted out between state and federal governments regarding the raising, processing, and selling of hemp as a commercial crop. Lydia Gray, DVM, MA, SmartPak Equine

  2. I’ve moved my 18-year-old TB gelding to another facility just up the road. After a month or so he began losing weight and several veterinarians examined him, determining it could be ulcers. He was then placed on an ulcer medication for several weeks, along with a high fat supplement and small amount of fortified grain. He was also supplemented with alfalfa hay along with grass hay through the winter months in which he was blanketed. He is slowly starting to put weight back on but riding is limited since he gets sore more easily even with a well-padded blanket and saddle and I’ve been working him over poles to help build his topline. Do you have any other suggestions on what we could be offering him, nutrition-wise, to gain weight and keep it on? (View Answer)

    It sounds like you’re doing everything right not only get to the bottom of why your horse might be losing weight in the first place as well as to get that weight back on safely. I’m sure the vets already mentioned dental care and parasite control to you, and maybe tested for other underlying medical conditions in addition to documenting his body condition score and body weight.

    Since it appears that he checked out fine, the next item on my list is food quantity and quality. What was the quantity (in pounds) and quality of hay at his original facility? Was there any access to pasture? What was the quantity and quality of grain at the previous location and how does all of this compare to what he is receiving now?

    Item number two is living environment. Don’t forget that he lost all his buddies in the move and had to make totally new ones, two stressful events for horses. In addition, is he able to eat in peace and quiet at the new place or are younger, stronger, more dominant horses driving him off his food or making him constantly worry and look over his shoulder? Horses can burn a lot of calories when meal-time = stress-time. 

    Let’s face it, some breeds are harder to put weight on than others, such as Thoroughbreds. And certainly as horses age into their teens and twenties their bodies begin to function less efficiently. However, this doesn’t mean that certain breeds or older horses have to be thin. It just means that they may need more veterinary care and improved diet and management to keep up their weight, like switching to a complete (senior) feed from regular fortified grain, adding beet pulp, or providing digestive support such as yeast, prebiotics, and probiotics.

    Although sometimes we never uncover the reason(s) for a horse to have difficulty keeping weight on, that doesn’t mean we aren’t able to stay on top of it with the additional measures you’ve already incorporated or trying some of the ones mentioned here. Lydia Gray, DVM, MA, SmartPak Equine

  3. What percent protein is actually absorbed by the horse's system? What protein percentage would be best? My horses are a 3-year-old filly, a 2-year-old stud and a 7-year-old. I may use the stud later for breeding, but currently just pleasure riding all three. (View Answer)

    Your question is actually much more complex than it seems on the surface, so I’m going to start out with the important protein facts that are necessary in providing a complete and balanced diet for the different ages and uses you describe.

    First, the percent of protein is not as important as the amount by weight of protein (and the first limiting amino acid, lysine), in a horse’s diet. The most recent version of the Nutrient Requirements of Horses (NRC 2007) lists these Daily Nutrient Requirements for horses with a mature body weight of 1100lb:

    Horse                                        Workload                                   Crude Protein (CP)                          Lysine

    2 yo colt                                 Pleasure riding (light exercise)      829 grams                                       35.7 grams

    3 yo filly                                 Pleasure riding (light exercise)       699 grams                                       30.1 grams

    7 yo adult                               Pleasure riding (mod. exercise)     768 grams                                       33.0 grams

    (I put your older, mature horse in the next category of work to show the difference)


    Your task now is to calculate the total amount of protein that you’re currently feeding each of your horses from all sources – hay, grain, plus supplements -- to make sure you’re at least meeting these minimum levels. For example, if you’re feeding 5 pounds of a 12% CP commercial, fortified grain, here’s that math:

    12% of 5lbs is 0.6lbs

    0.6lbs is 272g

    Once you add in the protein provided by hay or pasture, the total may reach the numbers above or it may not, in which case your choices are adding a protein supplement, improving the quality of your hay, adding more fortified grain, or switching to a grain with a higher percent protein.

    When nutritionists talk about the “quality” of a protein source, they’re referring to the amino acid profile. Right now, lysine is the only amino acid that is specifically required to be present in the diet, but generally we’re looking for feedstuffs to contain all 10 essential amino acids so all the necessary building blocks of protein are available for the body to use as needed.

    Finally, the topic of protein digestibility is one that is still under investigation and discussion by nutritionists. What we do know is that proteins digested in the foregut are more available to the horse than those that reach the cecum and hind gut before breakdown and absorption. Also, different protein sources have different degrees of absorption, with concentrates (grains) generally having a higher digestibility than forages (hay and pasture).

    Since you are feeding horses of different ages and uses – especially young, growing horses -- it may be best to consult with your veterinarian or a nutritionist to make sure you have the amounts, proportions, and sources all correct! Lydia Gray, DVM, MA, SmartPak Equine

  4. What is the right amount of hay to feed an adult horse per day? I have two Thoroughbreds that weight 1,000 and 1,200 lbs. Both are in their mid-teens in age. I typically put out a 40 lb bale of timothy/alfalfa in the morning and the same at night. Is that about right or is it too much? Please note that I do live in a colder climate, so my veterinarian had recommended free-choice hay in the winter to ensure they stay warm. (View Answer)

    Let’s take a look at the math first, then address other aspects of feeding horses since equine nutrition is both a science and an art. The rule of thumb is that horses should have at least 1% but preferably 2% of their body weight each day in forage (hay or pasture). That means:

    --Your 1000 lb horse needs between 10 and 20 lbs of hay each day

    --Your 1200 lb horse needs between 12 and 24 lbs of hay each day

    Together, the horses need between 22 and 44 lbs of hay each day. If you’re putting out a 40 lb bale twice a day, on the surface, this sounds like twice as much as your horses need (i.e. 80 lbs of hay a day). HOWEVER, there are several factors that can change the basic math or contribute to more hay being required to maintain a healthy weight:

    1. Thoroughbreds are known to be “hard keepers” with a metabolism that can burn up calories quickly, so it doesn’t surprise me that two Thoroughbreds can put away this much hay

    2. As horses age (and yours are in their mid-teens), some begin to lose their digestive efficiency, requiring more calories and other nutrients just to stay at the same weight and energy level.

    3. Extra hay is exactly the right thing to give to help horses stay warm in the winter, so during the cold months, additional flakes are an excellent idea.

    4. Horses in work require additional calories and reaching for hay to provide these is another great strategy.

    Now, 80 lbs of hay/day between two horses still seems a little on the high side to me, especially as part of the hay is alfalfa (what we call “ice cream” for horses in the Midwest!) and is not to be fed free-choice. Only grass hay should be available ad lib or 24/7. Are the horses wasting a lot of it? If so, then you may want to invest in an all-day hay bag or some kind of hay feeder that both protects the hay from being stepped on/laid on/defecated or urinated on AND slows down the rate of eating. There are more and more small hole hay nets and other devices to choose from every day. Just be sure to select one that is safe for unsupervised horses turned out in a group situation, like it sounds yours are.

    My final word on the subject is: don’t be pigeon-holed by the numbers. If your horses look great and feel great on the amount of hay you’re giving them, then ignore what the textbooks say as long as their body condition score is close to the ideal of 5, you’re confident their diet is otherwise complete and balanced, and their annual veterinary exam pronounces them in great health! Lydia Gray, DVM, MA, SmartPak Equine

  5. I have a 6-year-old grey Quarter horse gelding that I have recently found is homozygous PSSM2, and heterozygous P3 and Px based on hair analysis by Equiseq. I have changed his diet to approximately 5 lbs. Re-Leve, tri-aminos, vitamin -E (from Smartpack), and he gets magnesium. He is on free choice pasture and grass hay (we grow ourselves), and is moderately fleshy. His symptoms are exaggerated head tossing, rubbing of his nose, grunting, and lack of energy occasionally. Not only that, but he also has very sensitive skin when it comes to flies and fungus; fly sheets and masks get destroyed. I cannot seem to get any of his symptoms under control, and it is very difficult to exercise him. What am I missing in his diet, or what else can I do to help him? (View Answer)

    First, there is no scientifically validated genetic test for PSSM2, only PSSM1, so it is not accurate at this time to speak in terms of homozygous or heterozygous Polysaccharide Storage Myopathy that is not Type 1. And that is exactly the terminology that Dr. Stephanie Valberg, the Mary Anne McPhail Dressage Chair in Equine Sports Medicine and director of the Neuromuscular Diagnostic Laboratory in the Michigan State University Department of Large Animal Clinical Sciences calls PSSM2: “that which is not Type 1.” Taken directly from the website (which I suggest you visit):

    In 2008, a mutation in the glycogen synthase 1 gene was found to be highly associated with one form of abnormal storage of polysaccharide in muscle. Genetic testing of hundreds of horses previously diagnosed with PSSM showed that not all horses diagnosed with PSSM have this genetic mutation. This suggested that there are at least two forms of PSSM. For clarity, the form of PSSM caused by a glycogen synthase 1 (GYS1) gene mutation is now termed type 1 (PSSM1) whereas the form or forms of PSSM that are not caused by the GYS1 mutation and whose origin is yet unknown are now termed type 2 (PSSM2). In essence, a diagnosis of PSSM2 represents those horses in which a muscle biopsy shows clumping of muscle glycogen yet they do not have type 1 PSSM based on genetic testing. We do not know what causes PSSM2 and for the most part recommendations for type 2 PSSM have been the same as those for type 1 PSSM. We believe that there are probably several causes of PSSM2 and the best approach to managing PSSM2 may be to look at this in a breed specific manner.

    Here's why a proper diagnosis is so important: the first few signs you describe (head tossing, rubbing of his nose, grunting) sound more to me like headshaking syndrome than Polysaccharide Storage Myopathy. Have you talked to your veterinarian? Until your horse has been accurately diagnosed, any nutritional, management, exercise, medical, or tack and equipment adjustments are just guesses. I encourage you to visit Dr. John Madigan’s site to learn more about this syndrome, which has all kinds of useful info that might really help you:

    “Because exercise is associated with pain in these horses, they may be reluctant to move forward as they have become conditioned to expect pain during exercise.” Lydia Gray, DVM, MA, SmartPak Equine

  6. My horse lives outside and is a very chunky monkey. Even with a muzzle, she is still a body score of 7 and I ride her for an hour 5 days a week. She only gets a minimum amount of pellets (Grow & Win). I can't find any actual studies but several claims that fish oil/fat supplements help prevent laminitis as it reduces overall inflammation. Is it worth it to supplement in her diet? or wishful thinking and money better put towards a gym membership for my mare? What about salt supplements for a muzzled horse? (View Answer)

    To my knowledge, the only study that directly speaks to the role of fat supplementation in laminitis is this one:

    Essential Fatty Acid Supplementation as a Preventative for Carbohydrate Overload-Induced Laminitis. Neelley KA and Herthel DJ. 43rd Annu Conv Am Assoc Equine Pract 1997;43:367-70. Essential fatty acid supplementation prevents laminitis in horses challenged with carbohydrate overload. Possible mechanisms that would explain these findings include the known effects that essential fatty acids have on inflammation, vasoconstriction, hypertension, and coagulation in laboratory animals and man.

    And here is a paper that looked at the effects of hops:

    Inhibition of fructan-fermenting equine faecal bacteria and Streptococcus bovis by hops (Humulus lupulus L.) β-acid. Harlow BE, Lawrence LM, Kagan IA, and Flythe MD.J Appl Microbiol. 2014 Aug;117(2):329–39. The goals of this study were to determine if β-acid from hops (Humulus lupulus L.) could be used to control fructan fermentation by equine hindgut micro-organisms, and to verify the antimicrobial mode of action on Streptococcus bovis, which has been implicated in fructan fermentation, hindgut acidosis and pasture-associated laminitis (PAL) in the horse.

    You may want to consider ingredients like these as well as chromium, magnesium, and others, but I would urge you to take additional steps to help lower your mare’s risk of developing laminitis.

    Step one: Has your veterinarian been consulted? It’s important to know if you’re dealing with Equine Metabolic Syndrome and its associated laminitis and insulin dysregulation.

    Step two: Re-evaluate the diet. Unfortunately, there are some horses who just aren’t compatible with ANY amount of grazing, regardless of species of grass, time of day, or presence of a muzzle. You may be faced with having to build a dry lot for her. If you do, I strongly suggest a small hole hay net to reduce her rate of intake.

    Step three: Be creative with her exercise program. Especially if you are going to restrict her movement in a dry lot, she may need to work harder, longer, daily, or more than once per day if that’s possible for you. Whether you or someone else rides trot sets up hills in the morning and ground drives over poles at night, keeping her feet moving is good medicine.

    Step four: Speak of medicine, ask your vet if there are any prescription medications that might be appropriate to either “kick start” her metabolism for a short period of time or influence her insulin sensitivity and glucose metabolism.

    I hope this has been some helpful food-for-thought (for you, not your horse, as she seems to already be getting enough food!) Lydia Gray, DVM, MA, SmartPak Equine

  7. I am wondering if there are any concerns with lime in a horse's diet or if it will interact with any medication or supplements. (View Answer)

    I’m not entirely clear if you’re asking about lime the citrus fruit or agricultural lime aka limestone, which is calcium carbonate. If the former, while there are compounds in grapefruit that are known to interact with certain medications in people, I am not aware of any specific concerns among lime, lemons, or oranges. If the latter, there are several different types of “ag lime” so you’ll want to make sure you’re using the right one (some are for use on pastures and in stalls and some are to complete and balance the diet). Either way, I recommend you speak with your veterinarian to make sure adding “lime” to your horse’s diet is appropriate. Lydia Gray, DVM, MA, SmartPak Equine

  8. I recently changed hay from Bermuda to alfalfa and noticed that I don't have as bad a fly problem any connection? (View Answer)

    I am not aware of any connection between the type of hay fed to horses and the incidence of flies. If anything, I would think there would be MORE flies when alfalfa hay is fed because it contains more protein, which may result in stronger-smelling urine, thus attracting flies. However, what you’ve noticed may simply be a coincidence or due to something else such as the weather, a change in fly control practices, or another element. Lydia Gray, DVM, MA, SmartPak Equine