Why Does a Horse Lie Down?

Find out about equine sleep patterns from an equine behavior expert, and learn how to tell if the amount of time your horse spends lying down is normal.

Why Does a Horse Lie Down?

QUESTION:    Why do horses lie down?

ANSWER:     Lying down behavior in horses is a completely normal part of sleep. Horses are polyphasic sleepers, which means they have multiple, discrete sleep episodes in a 24-hour period. Time budgets show that horses spend one to three hours (adding up all sleep episodes) in a 24 hour period lying down, in both sternal (upright) and lateral (flat on side) recumbency. Differences are seen according to feeding and turnout management (horses tend to lie down less in constant turnout). We also know that foals spend more time recumbent and that gradually decreases as they age.

A horse can rest or doze in a standing position because of the stay apparatus in both the front and hind limbs, which allows their legs to “lock” in place. Horses lie down during deeper sleep states. Rapid eye movement (REM) sleep absolutely requires a horse to lie down. During REM sleep, while brain activity is actually increased, muscle tone is greatly diminished. Because of this loss of muscle tone, REM sleep in horses only occurs during lateral recumbency, or when a horse can lie in sternal and lean heavily against something. Horses spend only about a total of an hour in REM sleep over a 24 hour period.

Horses that don’t lie down and aren’t experiencing deep sleep might exhibit signs of sleep deprivation. A sleep deprived horse could repeatedly get very drowsy then collapse to his knees and suddenly wake back up (Dr. Joe Bertone [DVM, MS, Dipl. ACVIM] has studied this). Owners might not witness this behavior, but they might see unusual trauma to the knees and ankles. Some horses that are in musculoskeletal pain seem to resist lying down. We believe this is because of the additional pain or stress on legs with getting up and down. A horse might not lie down because he’s uncomfortable or insecure in his surroundings—lying down is a much more susceptible position for a prey animal. A new social situation or an unsatisfactory surface underfoot might also make a horse reluctant to lie down.

Alternatively, when a horse lies down for an excessive amount of time he could be suffering from a physical abnormality. Colic episodes can include a lot of rolling, but I have seen many colicky horses that just lie quietly. Musculoskeletal pain also might cause a horse to lie down. In my experience this is not with a single leg lameness but rather something more profound that affects multiple limbs, such as laminitis. Generalized weakness and incoordination associated with some neurologic conditions might also cause a horse to lie down excessive.

If you believe your horse is lying down too much or not enough, it might pay to put him under surveillance. You can review a 24-hour recording on high-speed and slow the video down during all his sleep episodes and get qualitative and quantitative data to compare to what’s normal or expected. Just be aware that if you must change your management for recording purposes you might also cause a change in rest and sleep behavior.

What sleep behaviors have you observed in your horses?


Prior to attending veterinary school, Dr. Nancy Diehl completed a master’s degree in animal science while studying stallion sexual behavior. Later, she completed a residency in large animal internal medicine at the University of Pennsylvania’s New Bolton Center and worked in equine practices in Missouri and Pennsylvania. Diehl also spent six years on faculty at Penn State, where she taught equine science and behavior courses and advised graduate students completing equine behavior research. Additionally, Diehl has co-authored scientific papers on stallion behavior, early intensive handling of foals, and feral horse contraception. Currently she is a practicing veterinarian in central Pennsylvania.

Early Stage Equine OA: Vets Consider 2.5% Polyacrylamide Gel Treatment

Researcher: Horses with osteoarthritis could one day benefit from a preventive approach using PAAG.

Early-Stage Equine OA: Vets Consider 2.5% Polyacrylamide Gel Treatment

In a “new uses for old things” twist, an equine veterinarian in Qatar has reported that a 2.5% hydrogel originally designed as a cosmetic filler can help horses with early stage to chronic osteoarthritis (OA) and could even one day be used to help prevent joint damage.

Florent David, DVM, MS, Dipl. ACVS & ECVS, Dipl. ACVSMR, ECVDI Assoc., specialist in Surgery, Sports Medicine & Rehabilitation, and Diagnostic Imaging at the Equine Veterinary Medical Center, in Doha, described what he found in published research on the product at the 2019 Northeast Association of Equine Practitioners Symposium, held Sept. 25-27 in Saratoga Springs, New York.

David began by explaining that there are two polyacrylamide gels designed for horses—Noltrex Vet (4%) and Arthramid Vet (2.5%). He said he has been involved with clinical research on both and hasn’t received renumeration or benefits from either company. More recently he’s conducted research on Arthramid Vet, which he focused on primarily in the current research review.

At the time of this presentation, scientists had not compared the two drugs directly but had completed and published individual research studies in peer-reviewed journals.

Doctors use a variety of hydrogels for cosmetology, and “they’re actually very different,” David said. “Polyacrylamide hydrogels are not all the same, and we should be aware of that.”

He said researchers in Denmark have reported the 2.5% gel is nontoxic, biocompatible, and stable with great tissue integration in joints from various species, including horses. “It’s a gel, produced by a patented technology, that’s basically made of a 3D network of cross-linked polyacrylamide polymers. During the manufacturing process water molecules are forced between the polyacrylamide chains, generating a porous biomaterial with great molecular stability and ability to maintain its viscoelastic properties in situ. The lightly bound water molecules in the gel can easily interchange with water from the surrounding tissue.”

The product is approved for use in New Zealand, he explained, and it’s awaiting approval for use in many other countries. David said scientists speculate that the gel works by improving the joint capsule elasticity lost during the osteoarthritic process. The gel might also protect the joint surfaces from exposure to cytokines, which are inflammatory molecules the immune system produces.

“The facts are little, I would say,” he added. “We know that the gel is integrated (into the joint), produces synovial hyperplasia, and this appears to give the joint a stabilizing effect on the joint capsule and synovium (lining) with a subsequent increase in elasticity and tensile strength. There may be more undiscovered effects, as well.”

David acknowledged that most of the 2.5% PAAG clinical studies have been uncontrolled, usually in cases that didn’t respond to typical intra-articular (IA) joint injections. Here are the studies he reviewed:

  • In 2012 Janssen et al. used 2.5% PAAG to treat 12 horses that had been lame for three or more months due to coffin joint OA. The veterinarians had diagnosed the horses using clinical signs, IA anesthesia (joint blocking), radiographs (X rays), and MRI, and all horses had been treated previously with triamcinolone acetonide and sodium hyaluronan, and/or autologous conditioned serum. The scientists injected the horses’ coffin joints with 1 milliliter of the 2.5% PAAG. They saw no side effects in any of the horses. Six months after the injections, eight horses (67%) were lameness-free, two were improved, and two hadn’t responded to treatment.
  • In 2014 Tnibar et al. conducted a controlled trial on the efficacy of 2.5% PAAG in fetlock joint OA. Forty sport horses were enrolled in the study—20 in each group. Veterinarians diagnosed OA using IA anesthesia, radiographs, and MRI and treated one group with 2 milliliters 2.5% PAAG and the other with 10 milligrams triamcinolone acetonide plus 20 milligrams sodium hyaluronate (TA-HA). Clinicians blinded to the treatment assessed lameness at one, three, and six months post-injection. “It outperformed triamcinolone at every time point,” said David, with 55% of horses in the PAAG group sound versus 15% in the TA-HA group at one month; 65% vs 40% at three months; and 75% vs. 35% at six months.
  • In 2015 Tnibar et al. studied 43 horses (65% sport horses, 19% racing, 16% others) with single-joint OA: 63% of the joints were in the forelimb, 93% were fetlocks, and 86% had undergone previous OA treatment. Clinicians performed a blinded assessment of lameness. At one, three, six, 12, and 24 months after injection with 2 milliliters 2.5% PAAG, 59%, 69%, 79%, 81%, and 82.5% of horses were lameness-free, respectively. He added that 78% of the horses had no joint effusion (fluid swelling) at the final time point.
  • Bathe et al. performed a prospective study in 20 sport horses with proximal/distal interphalangeal joint (pastern or coffin joint) OA-associated lameness in 2016. Veterinarians diagnosed all horses on MRI, and all horses were persistently lame after previous corticosteroid treatment for an average of 15-plus months. Horses were 3/10 lame on Day 0 and received IA injections of 1 milliliter 2.5% PAAG. Of 18 horses available for follow-up a median of 12 months later, 12 had returned to full function, three to a lower level, and three failed to improve.
  • In 2019 Clifford et al. (David’s research team) performed a pilot study in 89 painful joints in 49 flat-racing Thoroughbreds. Of those joints, 88% were mid-carpal (knee) and 12% fetlock, and none had received IA medication in the two months prior to the study. Lameness grades prior to injection were mainly 2/5 and 3/5 lame, with radiological scores of 0/3 and 1/3 in most cases; this indicated “no-to-mild OA changes on the radiographs,” said David. The clinician assessing lameness was blinded to what treatment the horses received; veterinarians injected 2 milliliters of 2.5% PAAG IA. There were no side effects or adverse reactions in any of the treated joints, and the percentage of lameness-free horses included:
    • 0% at one week;
    • 43% (21/49) at four weeks;
    • 3% (33/49) at 12 weeks; and
    • 3% (32/49) at 24 weeks (one horse regressed).

He explained that a further 14.3% (7/49) improved enough to remain in race training. “The largest reduction in lameness scores occurred at four weeks, with some taking up to 12 weeks after treatment to respond, and no further improvement in lameness between 12 and 24 weeks was observed,” he said.

“We came back with a single-site double-blinded prospective study on the comparative efficacy of 2.5% PAAG with intercarpal joint lameness,” he said.

They performed the study in 33 flat-racing Thoroughbreds with confirmed intercarpal (knee) joint pain based on clinical findings that included lameness, joint effusion, and reaction to flexion, along with IA anesthesia and radiographic assessment.

The team studied three treatment groups: The first received 2 milliliters 2.5% PAAG, the second 10 milligrams triamcinolone acetonide, and the third, 20 milligrams sodium hyaluronan IA, followed by two 40 milligrams intravenous (IV) injections at weekly intervals. The horses rested for 48 hours after the injection and resumed an unaltered training regimen. Clinicians examined the horses at two, four, and six weeks and continued to examine the 2.5% PAAG group through to 12 weeks. They based treatment success on whether the horse was sound.

“It definitively outperformed the other treatments, even in the early phase of joint pain/OA,” he said. “We looked at them at 12 weeks, (and) the horses that were lame-free at six weeks were still lame-free at 12 weeks with the 2.5% PAAG.”

Finally, David reviewed one uncontrolled, unblinded study on 4% PAAG, in which McClure and Wang (2017) noted a significant decrease in lameness score in 23 of 28 (82%) treated horses at Day 45 after treatment and 21 of 28 (75%) horses at Day 90, compared to baseline. He said there was “regrettably no data on the number of lameness-free horses in this study.”

“If you can improve your quality of life, that’s a different story,” he said. “If we are to look at something with those products, better to look at the lame-free, because this is what our industry is a lot about.”

Expectations and Moving Forward

David said veterinarians initially used PAAG for chronic OA cases, but he’s beginning to think it’s better to apply it earlier as a first-intention therapy.

“Some people are even talking prophylactic (preventive) use,” he said, “but we’re far from having data to support this.”

Here are some things he said veterinarians and researchers need to consider as they move forward in understanding and using PAAG:

  • Before treating a joint, it’s important to “prove the painful joint is really the painful joint.” Don’t pursue treatment unless you’re sure.
  • “(The PAAGs) are not miracle products, we need to be realistic of what to expect of them. Intra-articular fractures or osteochondral chips should still be treated surgically (fracture repair and arthroscopic chip removal) when indicated, and PAAGs are not made to replace surgery.” he said.
  • “There is anecdotal evidence suggesting PAAGs could be taking a share in the successful management of subchondral bone cysts, but proper data are lacking currently.”
  • “We should not wait to fire the PAAG bullet until we have obvious evidence of OA on the radiographs (before deciding to treat),” he said. “There is now evidence that early in the disease process PAAGs perform better than corticosteroids or hyaluronic acid.”
  • David broached whether veterinarians can combine the drug with other medications, noting that they might one day consider administering it along with bisphosphonates. “It’s better to give the drug on its own, but let’s say the horse is not responding,” he said, adding that there’s “no proof … at the moment.”
  • Veterinarians and horse owners need to keep in mind the delayed response to PAAG treatment—David says this delay is normal, but it’s not what clients are accustomed to with joint treatment. “PAAGs take three to four weeks, and sometimes up to six weeks, to take effect,” he said. “They are not anti-inflammatory drugs or painkillers and, as a result, it requires a different mindset of the trainer and owner expectations, compared to traditional therapies.”

He said the main and most important question today is how much to inject in each joint, a question he answered with a list of suggested doses (see sidebar). Post-injection protocols range from horses resting for 24 to 48 hours only before returning to training to four weeks of exercise restriction (swimming, water treadmill, hand/saddle walking) before return to proper exercise.

“There’s evidence to suggest a dose-dependent response,” he said. In other words, the smaller the dose, the less the response.

“Reassess the horses between three and six weeks. A second dose should be considered for ‘partial responders,’ especially if a low volume was injected first,” he said, noting that repeat doses can be given at six to 12 months, only if needed.

Overall, David is encouraged about the possibilities 2.5% PAAG presents veterinarians and lame horses.

“There is mounting evidence that these new products are a game changer in the management of joint pain in osteoarthritis, and I’m very glad we have those products available,” he said. “A lot of everything has been tried on the horses I usually see. I’m very happy to have this medication available, despite the high price. I’ve been able to return a large number of athletes of all kinds, struggling with their careers, to the sport.

“Based on their mechanism of action and their relatively slow integration in the synovial membrane to obtain benefits on the joint capsule elasticity and joint pain, PAAGs are not products that are under the radar from a doping point of view as painkillers and corticosteroids would be.

“It is a very, very safe product,” he added. “I’ve never had to go and flush a joint after hundreds of joints injected up to now. I sometimes get a mild flare, as you can get with any IA medication, but this is about it. In my hands, Arthramid Vet has been a very safe product to use.”


Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

Horse Feeding Basics

Confused about your horse’s diet? We’re here to help. Here’s how to craft the proper hay and grain ration.

Horse Feeding Basics

 Learn how to properly craft your horse’s diet

Providing a properly balanced equine diet is one of the most crucial parts of horse ownership, yet its complexity means it is frequently misunderstood or even overlooked. Whether you’re the only one who cares for your horse or you rely on boarding facility staff to help, you should have a basic understanding of proper horse feeding to be sure your horse is on an acceptable nutritional plane. If you need help developing a diet to meet your horse’s individual needs, your veterinarian, an equine nutritionist, and/or an extension specialist can be great resources.

For this article we’ve called on four equine nutritionists and extension specialists for their best feeding advice.

Evaluating Body Condition

The first step in crafting a horse’s diet, says Rhonda Hoffman, PhD, PAS, Dipl. ACAN, professor of horse science at Middle Tennessee State University, in Murfreesboro, is knowing whether he is healthy. “First, and most importantly, horse owners must be able to look at their horse and assess whether it is at a healthy weight or too fat or too thin,” she says. “The eye of the feeder fattens (or thins) the horse.”

Horse owners should acquaint themselves with the Henneke Body Condition scoring system that ranges from 1 (emaciated) to 9 (obese). The ideal body condition score is from 4 to 6.

“Five is ideal, and (these horses) should have moderate fat cover over the crest of the neck, behind the shoulders, over the ribs, and over the loin and tailhead,” says Carey Williams, PhD, associate professor and associate extension specialist at Rutgers, the State University of New Jersey, in New Brunswick. “Ribs should be easily felt but not seen. This will help the horse owner determine if the horse needs to gain or lose weight.”  

Understanding the Math

Next, you will need to know how much your horse weighs to calculate how much to feed him and what. Unless you take your horse to a facility that has a large-enough scale, such as a veterinary clinic or commercial farm, you will need to calculate his estimated weight using a weight tape. The formula differs depending on whether a horse is a young growing horse, a pony or draft breed, lactating or pregnant, in heavy work, underweight, or overweight. However, the general calculation for the average light horse breed is:

Body weight in pounds = (Heart girth in inches x Length in inches*) / 330

*Length of the horse is measured from the point of the shoulder blade to the point of the rump.

“A weight tape placed moderately tight (you should still be able to fit a few fingers under the tape) around the highest point of the withers around the girth area will give you a weight estimate plus or minus 50 pounds,” says Williams. Taking a measurement every two weeks should reflect any weight changes.

Bob Coleman, PhD, BSc, assistant professor and extension horse specialist at the University of Kentucky, in Lexington, suggests using technology to determine a horse’s weight. “There are a number of formulas, and more recently the University of Minnesota released an app called the ‘Healthy Horse,’” he said. “This allows horse owners a means to measure their horse and get an estimate of what it currently weighs and then an estimate of the horse’s ideal weight. That tells the owner where they are at and if the horse needs to gain, lose, or stay the same.”

Weight, along with age, amount of exercise, climate, body condition, reproductive status, type of horse (light horse, for example), etc., all affect a horse’s energy and nutrient requirements—the amount of calories, protein, fat, vitamins, and minerals he needs to consume.  

Start with Forage

Coleman and Williams suggest that horses consume 1.5-2.5% of their body weight daily in forage, with “easy keepers” on the lower end of that range (the “air ferns” of the horse world) and “hard keepers” (those who have trouble keeping on weight) on the higher end.

“Forage is the basis of all feeding programs, as this is a primary source of the basic nutrients needed,” Coleman explains. “Now, with that said, one can provide more than the horse needs, say with good pasture when a horse is at maintenance. The pasture intake is hard to limit unless you either restrict access to the pasture or use a grazing muzzle.”

So how do you know how much your horse is eating when he is out to pasture? Williams says a 1,000-pound horse in light work can consume 20 pounds of forage—grass and hay—per day. “You can assume that if they are out (to pasture) for eight hours, they will eat approximately one-third of their daily intake, so the remaining two-thirds of the day they are in the stall, they could eat the remaining, roughly 13-14 pounds.”  

Offer as much as possible of this remaining amount as other forms of forage, such as hay, and then only add grain if your horse needs it to meet his energy needs.  

Laurie Lawrence, PhD, professor in the Department of Animal Sciences at the University of Kentucky, says owners should remember that pastured horses are subject to dietary changes associated with pasture availability. Therefore, additional hay might be necessary if pasture quality declines.

If a horse is accustomed to always being on pasture, Hoffman says the owner will need to introduce any supplemental hay and/or grain into the diet gradually. The same is true for returning horses to pasture in the spring as well as in the fall after a frost: Do so gradually, as sugar levels in grasses increase during these times, which can, in turn, increase a horse’s colic or laminitis risk. In these situations, “start with a couple of hours at a time for two to three days, and then increase that by two hours every three days until the horse is out as long as you wish it to be,” Hoffman suggests. This also allows the microbial population in the horse’s gut that aids in food digestion to adjust to the pasture.

Feeding high-quality hay free-choice in addition to pasture could exceed some horses’ nutrient requirements, warns Coleman. He recommends owners learn about the nutrients that different forage types provide. For instance, a legume hay, such as alfalfa, is higher in calories, protein, and calcium than grass hay of a similar maturity. Grass hay usually provides all of the calories the “average” horse needs.

Hoffman suggests owners enlist their hay or feed dealer or local extension specialist to perform a nutrient analysis on their hay. “This $20-30 investment is small compared to the price of hay and feed, and it can help you better understand what sort of feed to buy to balance the nutrients in the hay,” she says. “If your hay is nutrient-rich, you can likely save money (by feeding) a less-expensive grain. As well, it is easier to justify a higher calorie, higher protein, more expensive grain concentrate if your hay is lower in nutrients.”

Horse owners all have their own hay preferences, but Coleman says his top choice is a mixed alfalfa-grass hay that meets many different horse classes’ requirements, from growing to performance to senior horses. Williams prefers a grass hay that meets the needs of a horse in maintenance, which includes 8-10% protein and adequate levels of vitamins and minerals.  

Regardless of your choice, know how much hay you’re feeding by weight, not volume, says Williams. Feeding hay by volume (e.g., two flakes per feeding) can result in inconsistencies, because flakes can weigh different amounts. Also inspect hay for brown, black, gray, or white spots, which are indicative of mold. Quality hay should be pale to medium green and not smell dusty, dank, or moldy, Hoffman says.

Does Your Horse Need Grain?

As mentioned, if your horse is not getting all the nutrients he needs from forage, then you might need to add a concentrate feed to his diet.

“Exercise increases the amount of calories a horse needs,” says Lawrence. “Growing horses have comparatively higher needs for calories, amino acids, minerals, and vitamins than most mature horses. Nutrient requirements also increase during gestation and lactation. Diets for pregnant and lactating mares must contain adequate nutrition or the mare will rob her own body stores to some extent to support fetal growth or milk production.”

Lawrence adds that good-quality commercial feeds usually contain adequate amounts of vitamins and minerals for the class of horse the label specifies. Again, feed by weight.  

“If you obtained a commercially manufactured sweet feed and looked closely, it will probably contain some pellets,” explains Lawrence. “In many cases these pellets contain the nutrient fortification in the diet, particularly in vitamins and minerals. This pelleted material is often referred to as a ‘balancer,’ because it is used to provide a balanced nutrient profile in the feed. Some feed companies sell this type of pellet alone and call it a ‘ration balancer.’ If a horse is getting all the calories he needs from forage alone, feeding a small amount of the ration balancer will ensure that he gets all of the minerals and vitamins as well.” Coleman recommends feeding one to two pounds daily if using a pelleted balancer, based on the horse’s body condition and nutrient needs.

As for the choice of grain, Hoffman suggests horse owners choose a commercially mixed and balanced grain concentrate rather than feeding basic grains, such as oats, or trying to mix your own feed to save a few bucks. Without a nutritionist’s help, chances are you’re going to end up with a feed that does not provide balanced nutrition or that your horse must eat more of to get enough nutrients.

“As a general rule where grain is concerned, you get what you pay for,” Lawrence adds, suggesting that you might have to purchase a mid-range to above-average priced feed to get the best balance between cost and quality ingredients and nutrients.

Horse rations should contain 1.6-1.8g of salt per kg of dry feed matter.

Water and Salt

Due to their size, horses must consume a large volume of water to keep their bodies functioning normally. A mature average-sized horse will drink 5 to 10 gallons per day. Of course, factors such as exercise, hot temperatures, humidity, sweating, pregnancy or nursing, and increased hay intake multiply the amount of water a horse needs, sometimes up to three or four times the normal amount.

Make sure your horse always has free access to plenty of fresh water. Without enough water, impaction colic becomes a big risk, and an extended time without water can even result in kidney failure, brain damage, or organ shutdown.  

“Horses will typically drink two quarts (half a gallon) of water for every pound of hay they consume,” says Williams.  

Nutritionists also recommend that horse rations contain 1.6-1.8 grams of salt (sodium chloride) per kilogram of dry feed matter (what feed would weigh if all of the moisture were to be removed). Owners can provide additional salt through a mixture of one-third trace mineral or plain salt top-dressed on feed and two-thirds free-choice dicalcium phosphate (e.g., a salt block). This allows horses to meet their calcium and phosphorus needs as well, because these nutrients are not included in trace mineral salt blocks.  

Take-Home Message

If you are new to feeding horses, check with your veterinarian or an equine nutritionist to make sure his diet offers the nutrients he needs. Otherwise, he could develop serious health problems.


Sarah Evers Conrad has a bachelor’s of arts in journalism and equine science from Western Kentucky University. As a lifelong horse lover and equestrian, Conrad started her career at The Horse: Your Guide to Equine Health Care magazine. She has also worked for the United States Equestrian Federation as the managing editor of Equestrian magazine and director of e-communications and served as content manager/travel writer for a Caribbean travel agency. When she isn’t freelancing, Conrad spends her free time enjoying her family, reading, practicing photography, traveling, crocheting, and being around animals in her Lexington, Kentucky, home.

Opossums: The Scourge of a Horse Owner’s Existence?

Opossums are the culprits that transmit the causative parasite of EPM to horses. Dr. Dan Howe of the University of Kentucky recommends making an effort to keep them out of the barn and away from the food and water supplies.

Opossums: The Scourge of a Horse Owner’s Existence?

QUESTION:     Can you explain more about opossums and equine protozoal myeloencephalitis (EPM)? At one time we were all told that opossums are a host of EPM and help spread the causative parasite, but with the prevalence of opossums and horses in Kentucky, shouldn’t it be an epidemic? Can you share insight into EPM, how it is contracted, and if opossums are, indeed, the scourge of a horse owner’s existence? Is there any truth to the hypothesis that cats can spread it, too? And do we absolutely have to hate and wage war on opossums lest they cross our horses’ fields and infect them? I know they have some benefits to our world since they eat so many ticks and almost never carry rabies due to their low body temp. I am tired of everyone I meet hating opossums and wanting to kill each one they encounter. Any information pro or con would be appreciated; maybe I am not as anti-opossum as I need to be.

ANSWER:      You are correct that opossums (not cats) are the host animal that transmits Sarcocystis neurona, the protozoan parasite that causes EPM. You are also correct that opossums are everywhere in the Bluegrass region, and they’re not very selective in where they defecate (the mode of parasite transmission). So, it’s not too surprising that many horses in this area (>75%) have been infected by S. neurona, as revealed by the presence of antibodies against the parasite circulating in their blood.

The disease is not an epidemic, however, because most horses are apparently able to control the infection. It would seem that there is a small subpopulation of horses that are susceptible to the disease. Unfortunately, we don’t understand what factor(s) make horses more likely to progress to full-blown EPM when exposed to the parasite. It could be something intrinsic in the horse (for instance, its genetics), or it could be some external factor that causes the horse to be more susceptible (environment, nutrition, co-infection with a virus, etc.) Logically, a more complete understanding of this aspect of the disease would help us better control it, either through preventive measures (change in environment/nutrition), prophylactic treatment with a drug, or (ideally) with a logically designed vaccine.

Bottom line: Yes, opossums are the culprit that transmits the causative parasite of EPM to horses. While efforts to remove opossums will reduce the risk of infection on a farm, “nature abhors a vacuum,” as they say, and new opossums are bound to migrate into areas where the population has been reduced. Thus, I don’t think it’s feasible to completely stop horses from getting infected. I can acquire several different pathogens from my dog and cat, but I don’t intend to get rid of them because of it (although the cat does get on my nerves sometimes!). I do, however, keep the cat’s litter box far from where food is stored, and I think the same logic applies to opossums. Make an effort to keep them out of the barn and away from the food and water supplies. You won’t completely prevent a horse from being exposed to the parasite, but perhaps less frequent exposure will also reduce the likelihood of EPM occurring.

Daniel K. Howe, PhD, UK Gluck Equine Research Center
University of Kentucky

Understanding Gene Expression and Physiology During Equine Pregnancy

Understanding Gene Expression and Physiology During Equine Pregnancy
A recently published study has resulted in a significant step forward in understanding the physiology of pregnancy. Shavahn Loux, PhD, a postdoctoral scholar within the University of Kentucky Gluck Equine Research Center, conducted this work in conjunction with fellow Gluck Center researchers and scholars Pouya Dini, DVM, PhD, Dipl. ECAR, ACT; Hossam El-Sheikh Ali, PhD; Theodore Kalbfleisch, PhD; and Barry Ball, PhD, DVM, PhD, Dipl. ACT, Albert G. Clay Endowed Chair in Equine Reproduction.The study, titled, “Characterization of the placental transcriptome through mid to late gestation in the mare,” resulted in several notable firsts.

“This paper represents the first comprehensive look at gene expression in the placenta (fetal and maternal) in the middle to late time points of pregnancy and should provide researchers with vital information about the interaction occurring at the feto-maternal interface as pregnancy progresses,” Loux said. “By better understanding the gene expression landscape during pregnancy, this work provides a significant step toward understanding the physiology of pregnancy, thereby aiding the identification of novel drug targets and reducing the incidence of late-term abortions.”

She said the study also helps establish the horse as a valuable model for investigating biological communication between the developing fetus and the mother, or feto-maternal communication. The study demonstrated the ability to effectively separate maternal and fetal components of the placenta, with only a minimal amount of chorioallantoic (fetal membrane) contamination in the endometrium.

“The placenta is a dynamic organ which undergoes extensive remodeling throughout pregnancy to support, protect, and nourish the developing fetus,” the study abtract reads. “Despite the importance of the placenta, very little is known about patterns of gene expression in placental cells beyond very early in pregnancy and after birth (postpartum).”

“I used a technique called RNA-sequencing to analyze gene expression in the fetal (chorioallantois) and maternal (endometrium) aspects of the placenta at multiple gestational ages (4 months, 6 months, 10 months, and 11 months),” Loux said.

She and her collaborators found that within the maternal endometrium, 47% of genes changed throughout pregnancy, while in the fetal chorioallantois, 29% of genes underwent significant changes in expression. Through bioinformatic analyses, the researchers found that tissues were more similar than different, with about 95% of genes expressed in both tissues and high similarities between the most highly expressed genes. Genes expressed at the highest levels fell into a few broad categories, including endocrine and immune-related transcripts, iron-binding proteins, extracellular matrix proteins, transport proteins, and antioxidants.

“Overall, these data represent the first large-scale characterization of placental gene expression in any species and include time points from multiple mid- to late-gestational stages, helping further our understanding of gestational physiology,” Loux said.

To see the published research article in its entirety, visit https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0224497.

Holly Wiemers, MA, APR, is the communications director for UK Ag Equine Programs.

Sugars and Peppermints: Not Safe Treats for All Horses

Horses with certain health conditions should skip sweet treats. Find out if your horse is one.

Sugars and Peppermints: Not Safe Treats for All Horses
QUESTION   : Is it okay to feed my horse peppermints and sugar cubes? I’m concerned about the amount of sugar they contain. If it is okay, how many is too many?ANSWER:   Simple sugars, such as the sucrose found in peppermints and sugar cubes, are absorbed by the horse’s small intestine as glucose and fructose. Glucose causes release of insulin to facilitate the entry of glucose in to cells. Fructose (not to be confused with fructans) is metabolized differently. Only metabolized in the liver, fructose is more lipogenic than glucose, meaning that it’s more likely to lead to production of fat.

Most concern about sugar and starch intake has stemmed from our increasing knowledge about insulin resistance (IR), laminitis, polysaccharide storage myopathies (PSSM), and equine gastric ulcer syndrome (EGUS). Horses with IR release more insulin than is normal in order to remove glucose from their blood stream. As a result, while circulating glucose tends to be normal, circulating insulin is elevated. High circulating insulin creates an increased risk for developing laminitis. Horses with PSSM store glycogen (the storage form of glucose) abnormally in their muscle tissue, and diets high in starch and sugar cause increased production of volatile fatty acids in the gastric stomach causing a more acidic environment and a greater likelihood of a horse developing EGUS

I think it’s important to put the questions of sugar in treats in perspective of a horse’s typical daily non-structural carbohydrate consumption. If we assume a 1,200-pound horse eating 2% of body weight as dry matter from hay a day, and that the hay contains 10% moisture and 10 % nonstructural carbohydrate (NSC) on a dry-matter basis (a value often used as the recommended upper NSC level for horses with metabolic issues, such as IR and PSSM), this horse is consuming 1,090 grams of NSC (starch and simple sugars) per day.

A pure sugar cube weighing about 4 grams is 100% sucrose. The popular round, red-and-white peppermint candies have a human serving size of three pieces (about 15 grams) and of that between 8 and 10 grams are sugar. Traditional peppermint candy canes are heavier at 18 grams and provide about 12 to 14 grams of sugar. You can see that in the context of the above horse’s daily diet these are tiny intakes of sugar. However, there are some important considerations.

When feeding a horse hay, you’re also feeding it proteins and minerals that help buffer stomach acid. Additionally, hay’s fiber component impacts the rate at which the NSC reaches the small intestine and is absorbed. The sugar in sugar cubes dissolves quickly and will move with the liquid fraction of the digesta, which moves more rapidly than larger fibrous particles. This means that that the sugar will likely be absorbed relatively soon after it is fed. This makes it potentially more likely to cause a spike in blood glucose than the NSC contained within hay.

Feeding a healthy horse three or four sugar cubes is unlikely to cause a significant glucose spike; however, for a horse with uncontrolled IR, PSSM, or a laminitis history, feeding sugar cubes isn’t a risk worth taking. Skip the sugary treats, too, if your horse is overweight, especially if he has a cresty neck. After all, every calorie counts and calories from treats mean feeding fewer calories from “real” food. Human research shows that tissues in insulin resistant people are more sensitive to insulin after exercise. This may or may not be the case in horses, but if it is, then your horse might be better able to handle the sugar in these treats when they are given shortly after work.

For the otherwise healthy horse, consuming a candy cane or a few peppermint candies is unlikely to have any major impact.


Clair Thunes, PhD, is an equine nutritionist who owns Summit Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club.

Ideal Feed Frequency for Horses

How often should you feed your horses each day? Our nutrition expert weighs in with advice.

Ideal Feed Frequency for Horses

QUESTION  . I’m considering moving my horse to a barn where he will get some turnout. I have found several possibilities, and some have more amenities than others. I’m noticing a difference between barns in number of meals per day and time between feedings. At our current barn he gets fed forage twice a day, but I’m wondering what the ideal length of time between forage meals is when a horse isn’t continuously grazing?

ANSWER:  Horses in their natural setting spend most of their time eating. As a result, they secrete stomach acid constantly, which is buffered by the saliva released while they chew their food. Conversely, many horses today are kept in stables for at least some or all of the day and are fed discrete meals. Most commonly, horses receive two meals a day, although some barns with the ability to do so will feed three or more times a day.

Obviously, the more frequently a horse receives forage, the more similar his environment becomes to the way horses evolved. The risk for conditions such as gastric ulcers and colic lowers, as do stereotypic behaviors linked to boredom and stress, such as weaving and cribbing. The horse’s stomach is mostly empty about six hours after being fed, with nearly all the larger fibrous particles passing within 12 hours.

Therefore, it’s ideal to ensure horses are fed forage at no more than six-hour intervals. While this might be doable during the day, it’s unlikely to be feasible to feed very late at night or in the very early hours of the morning. To keep some forage in the stomach, I would ensure that horses are fed breakfast no more than 12 hours after being fed dinner.

A possible feeding schedule would be along the lines of 7 a.m. breakfast, 3 p.m. lunch, and 11 p.m. dinner. While this schedule spaces meals out nicely at eight-hour intervals, it is not very realistic, except perhaps for those keeping horses at home or with very small boarding barns. More realistic would be to feed meals at 6 a.m., 1 p.m., and 6 p.m. with the possibility of a fourth meal at, say, 10 p.m. This would provide forage at no more than eight-hour intervals.

Of course, barns can make hay last longer and reduce the time between meals by using hay slow feeders such as small-holed haynets. This can make a forage meal that a horse would normally consume in an hour last several hours. Automatic pellet dispensers also exist that you can use to feed hay pellets at predetermined times such as the middle of the night. These can be particularly helpful when you do have longer periods between hay meals.

While some barns offer horses continuous forage access, this might not be appropriate for all horses if the quantity consumed is not controlled. Easy keepers will balloon in this scenario, gaining undesirable amounts of weight. Again, small-holed haynets can be very useful in these situations, as they allow for a controlled amount of total forage consumed while making that consumption last longer.

I commend you for taking feeding frequency into consideration as you shop for a new boarding situation for your horse. While things such as arena access, footing, availability of trails, etc. are important factors to us as riders, your horse likely doesn’t care about most of these things. He will likely be much happier is a situation where he gets fed frequently when not on turnout. You yourself might see the benefits of reduced colic and gastric ulcer risk.

About The Author


Clair Thunes, PhD, is an equine nutritionist who owns Summit Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club.


Hoof Radiographs: More Than Meets the Eye

Something on the X rays looks a bit off–is it significant or of no consequence? It depends on what you find.

Hoof Radiographs: More Than Meets the Eye

Something on the X rays looks a bit off—is it significant or of no consequence?

The signs are subtle and they’ve come on slowly, but it’s become quite clear that your mare is lame. She shifts right to left and back again, like ocean waves lapping the shore, making it difficult to know exactly what hurts. Just about the only thing you can grasp from watching the changing tides of her lameness is which foot is affected.

You call your veterinarian, who conducts a complete examination that includes radiographs (X rays) of your mare’s foot. The resulting images are far from textbook, but which structural changes are causing her pain? And which ones are likely little reason for concern?  

“An X ray might be black and white, but interpreting those X rays and deciphering what ‘abnormalities’ are important and which aren’t are definitely filled with shades of gray,” says Tracy Turner, DVM, MS, Dipl. ACVS, ACVSMR, of Anoka Equine Veterinary Services, in Elk River, Minnesota.

In this article we will delve deeper into the radiographic changes that owners and veterinarians might (or might not) find on the X rays of chronically lame, acutely lame, acutely lame due to wounds or trauma, and even nonlame “healthy” horses.  

Considering the Chronically Lame

Onset of chronic lameness is typically slow or on-again-off-again—you might spend months wondering if you actually need to call the vet. Ongoing or recurrent lameness in horses commonly stems from two conditions. One is navicular disease/syndrome, which is forelimb lameness associated with pain in the navicular bone, which lies at the back of the horse’s hoof capsule, and related structures. The other is laminitis, which happens when the tissues that suspend the coffin bone, or third phalanx, inside the hoof fail. Veterinarians can use radiographs to diagnose the disease responsible for a horse’s chronic lameness, as well as follow its progression.

Expected findings

Horses with navicular disease typically have “classic” radiograph findings, making diagnosis fairly straightforward. Veterinarians recommend taking a minimum of five views—X rays captured from different angles—to diagnose or evaluate navicular disease. On those radiographs you might see:  

  • “Lollipop” or “cone” shapes that aren’t as white as the normal surrounding bone at the distal (lower) border of the navicular bone;
  • Calcification, the formation of excess mineral deposits that eventually harden to bone, which causes the proximal (upper) or distal borders of the navicular bone to appear more white than normal;
  • Bone loss or changes along the flexor surface of the navicular bone (the underside, around which the deep digital flexor tendon, or DDFT, runs to meet the coffin bone); and
  • In some cases, “holes” (bone lysis/destruction) or cysts in the navicular bone, which again appear less white than normal.   

For horses with chronic laminitis, common radiographic findings include “sinking” or “rotation” of the coffin bone. You might also see bone loss or remodeling of the coffin bone.

Unexpected findings

Rarely, veterinarians find cystlike lesions in the coffin bone, bi- or tripartite navicular bones (i.e., the bones are not completely calcified and appear to be fractured in two or three pieces, but aren’t), and distal border fragments of the navicular bone. These cause pain in some horses but are inconsequential for others.

“In some Warmbloods, distal border fragments of the navicular bone show up frequently, with or without any associated lameness,” notes Turner.

If your veterinarian notes any of these on radiographs, he or she might recommend additional diagnostic imaging techniques, such as MRI and ultrasonography, or even referral to a specialist to help determine if those uncommon findings are contributing to foot pain.  

Assessing the Acutely Lame Horse

Aside from trauma or injury, a variety of conditions can cause acute, or sudden and severe, lameness. Many soft tissues in the foot, including the DDFT and distal sesamoidean impar ligament, can be damaged. An abscess or bruised sole can cause a rapid-onset lameness so severe it looks like the horse has fractured a bone. It is important to note that soft-tissue injuries, abscesses, and bruises don’t always (or even typically) manifest radiographically because there isn’t enough contrast between those tissues to “distinguish” what is wrong.

Expected findings

“In an acute severe lameness, my differentials are abscess (of the soft tissue structures of the foot) or fracture of either the coffin or navicular bone,” says Turner. “The collateral cartilage (located on either side of the coffin bone, thought to function in hoof expansion/shock absorption) can fracture, but this is rare. More often, people see a calcified collateral that is incompletely calcified (on the X rays), and it looks like a fracture but is not.” This would be diagnosed as sidebone.

It’s important to note that a fracture can take 10 to 14 days to reveal itself because the hoof capsule does not allow obvious bone displacement. Rather, space between fractured pieces of bone is what veterinarians observe on X ray to help diagnose a fracture.

Foot abscesses might be visible on radiographs, but only if gas (produced by bacteria in the abscess) provides contrast between the pus and the hoof tissues and delineates abscess location. Luckily, Turner says, “The new digital radiographic systems are better at finding abscesses because they give you better contrast changes in the soft tissues compared to traditional systems.”  

Unexpected findings

Veterinarians that anticipate a fracture of some kind in an acutely lame horse might also stumble across other “hitchhiking” radiographic lesions. These freeloaders include virtually any conceivable sort of chronic change due to degeneration or osteoarthritis, navicular changes, etc. Although the term “chronic” implies long-standing, be aware that these changes can occur even in young horses that have undergone musculoskeletal stress.  

Although laminitis does not usually occur unilaterally (in one foot only), the practitioner should not rule it out completely in an acutely lame horse. A horse can develop unilateral laminitis if he is sufficiently lame on the complementary limb, resulting in more weight bearing on the uninjured limb. As a result, the once-sound limb is now the primary problem, a condition commonly referred to “supporting-limb laminitis.”

Wounds and Trauma: Imaging the Acutely Injured

Sure, horses might seem lithe and graceful, but they are ridiculously accident-prone, with their feet frequently falling victim to trauma and/or injury. Again, veterinarians are unlikely to note soft-tissue injuries via radiography, but they can use X rays to rule out bone and/or joint involvement in injured horses, such as those with wounds or blunt trauma from a horse kicking a stall wall, for instance.

Expected findings

Veterinarians must look for foreign bodies, fractures, and soft-tissue injuries in injured horses. In addition to “plain” radiographs, practitioners can use a commercial contrast agent that shows up on X rays to help analyze wounds (e.g., whether a wound enters a joint space) along with bursas (fluid-filled structures near joints) and other structures. Turner encourages veterinarians and owners to explore this option, saying, “Contrast agents can give important insight into surrounding soft tissues.”

Unexpected findings

Surprise findings can crop up when radiographing an injured horse with no previous history of lameness.  

“For me, any chronic changes or OCD (osteochondritis dissecans) fragments, etc., are unexpected and must be assessed and explained as to their relation to the lameness,” says Turner.

The Prepurchase Picture

Many seemingly healthy, sound horses undergo routine prepurchase exams before sale. Just to be thorough, most veterinarians recommend taking radiographs of the foot (and frequently other joints, such as the stifles, hocks, fetlocks, or knees, depending on breed). In some cases the prepurchase examination can be an “angst-ridden procedure for the vendor, purchaser, and the examining veterinarian!” says Sarah E. Powell, MA, VetMB, MRCVS, partner at Rossdales Equine Diagnostic Centre, in Newmarket, U.K.

The purpose of the prepurchase examination is to determine if the horse is “fit for purpose,” like in the decision tree below, which can be easier said than done.

“During a prepurchase examination it is not uncommon to identify radiographic abnormalities, especially in a sport horse or racehorse,” she says. “Experience is necessary for determining the relevance (of the radiographic findings) to that particular individual. Not all horses with abnormal X rays will go on to develop lameness. Conversely, a horse which shows lameness during the examination may have normal X rays.”

Expected findings

Powell explains that what you might expect to find in an apparently sound horse’s foot varies, depending on age and how many miles are on the clock. “As a horse ages, the bones and joints, particularly of the lower limbs, accumulate signs of wear and tear due to repetitive loading stresses,” she says.  

Stress-caused damage detectable on radiographs includes:

  1. Increased bone density sclerosis (see sidebar, page 39), which appears whiter on radiographs than normal bone.
  2. Remodeling changes, particularly around joint margins. These can represent either adaptive changes, which are necessary to strengthen bone, or maladaptive changes (harmful ones such as bone bruising). A proportion of horses with maladaptive changes might either be lame at the time of examination or at risk of developing lameness.  

It’s important to recognize that breed differences can affect what you see on foot radiographs, whether the horse is sound or unsound: “Heavier horses and draft breeds, for example, can have quite dramatic bone remodeling surrounding the (high-load-bearing) pastern joint, which should not be confused with osteoarthrosis,” Powell says. “They can also have quite dramatic modeling of the bony attachments of the collateral ligaments of the coffin joint. In a fine-limbed breed that latter change could be a sign of ligament disease, and there would be a greater cause for concern.”

Unexpected findings

“We occasionally get a surprise when taking radiographs of a sound horse with no previous history of lameness, including large subchondral (located just under the cartilage surface within a joint) bone cysts or bone fragments either at the margins of joints or at the site of the major soft-tissue attachments within the foot,” Powell notes.  

In a small number of yearlings undergoing presale radiographs, she and her colleagues have seen bi-partite navicular bones, which she says are congenital (present at birth). “Both of these types of findings may be a real concern for future soundness, particularly when seen in young, unproven horses,” she says.  

Be aware that degenerative changes, such as sidebone or the chips off the navicular bone mentioned earlier, might also appear on X rays.  

“These changes do not just occur in older horses, as they have little to nothing to do with age,” says Turner. “Although ‘arthritic’ changes frequently occur with age, we also see age-related remodeling of both the coffin bone and navicular bones, which are more accurately considered degenerative changes.”  

Again, these degenerative changes might or might not be clinically relevant, and your veterinarian must interpret them based on physical exam findings and the horse’s history.

Which Findings are Relevant?

So now that we know what various expected and unexpected findings might crop up on a foot radiograph, its time to ask: Which ones are causing lameness, or is it something else entirely?

“A thorough clinical examination is extremely important, of course, which gives invaluable information as to the foot shape, conformation, and quality of the hoof horn, etc.,” Powell says. “A small region of bone resorption in the margin of the pedal bone (coffin bone) can indicate a number of things, but if a crack is present in the hoof at this level, and the crack is painful when hoof testers are applied, then this has added relevance.”

In some instances the presentation of the lameness itself gives clues as to the underlying cause or renders certain radiographic findings more significant than others. For example, a veterinarian examining the horse will piece together the radiographic information with observations such as whether the lameness is worse on hard or soft ground or if it’s worse with the affected limb on the inside or outside when circling.

To complicate matters more, poor-quality radiographs and not quite catching the “right” angle can also impact a veterinarian’s ability to interpret X rays. These factors can cause radiographic “artifacts,” or abnormalities due to poor technique, patient movement, etc. These can be misleading during diagnosis.

So, how do you know if your rads are rad or if you are being had?  

Renate Weller, DVM, PhD, MSc, Vet Ed, MRCVS, professor of comparative imaging and biomechanics at the Royal Veterinary College in Hertfordshire, U.K, says it’s quite simple: Can you see everything you are interested in?

One of the best ways to minimize radiographic artifacts is to prepare the horse’s foot properly for the procedure.

“Although there are exceptions to the following ‘rules,’ it is preferable to remove the horse’s shoes, trim the foot with hoof knives to remove loose horn and dirt, pack the foot with Play-Doh, and place a metal marker on the dorsal hoof wall (the front of the hoof) and a pin in the Play-Doh in the front of the frog,” Weller says.  

Yes, movement of either the horse or the person holding the plate during the radiograph can blur the image. What makes the “clinical picture” blurry, however, is when the veterinarian identifies more than one abnormality.  

Always entertain the idea that more than one issue can be the cause of any lameness, says Mathieu Spriet, DVM, MS, Dipl. ACVR, Dipl. ECVDI, associate professor of Clinical Surgical and Radiological Sciences at the UC Davis School of Veterinary Medicine.  

“If we consider that multiple abnormalities could be contributing to the lameness, we will ultimately have more success treating foot pain,” he says. “For example, horses can injure both the deep digital flexor tendon and the distal sesamoidean impar ligament simultaneously. In turn, those injuries can cause resorption or breakdown of the coffin bone and promote the formation of cystlike lesions of the bone.”

Take-Home Message

There’s more to capturing and interpreting foot radiographs than shooting a few views of a horse’s feet, watching him trot, and calling it XYZ condition. Careful preparation of the horse and good-quality X rays will help practitioners obtain as much information as possible. In complex cases, additional diagnostic imaging approaches might be beneficial.


Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she’s worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

Racehorse Breakdowns: Prosecutor’s Probe Finds No Wrongdoing at Santa Anita

After an investigation, the Los Angeles County district attorney found no evidence of wrongdoing by Santa Anita Park operators in connection with a series of racehorse deaths there.

Racehorse Breakdowns: Prosecutor's Probe Finds No Wrongdoing at Santa Anita
After an investigation, Los Angeles County District Attorney Jackie Lacey found no evidence of wrongdoing by Santa Anita Park operators in connection with a series of racehorse deaths at the Arcadia, California, track.Between July 1, 2018, and November 30, 2019, 56 horses either died or were euthanized as the result of injuries sustained while training or racing at Santa Anita Park.

In response, track operators asked Mick Peterson, PhD, professor of biosystems and agricultural engineering at the University of Kentucky, to thoroughly examine the surface conditions at Santa Anita. The evaluation revealed no track-related link to the fatalities, Peterson said.

Meanwhile, the California Horse Racing Board (CHRB) launched its own investigation into the deaths and, in April, Lacey announced that her office had formed a task force to probe the incidents.

On Dec. 19 Lacey released a 17-page report absolving Santa Anita’s operators of wrongdoing in connection with the deaths.

“After a thorough investigation and review of the evidence, the district attorney’s task force did not find evidence of criminal animal cruelty or unlawful conduct relating to the equine fatalities at Santa Anita Park,” the report said.

In a written statement, Santa Anita Park operators, The Stronach Group, praised Lacey’s office for its “robust” investigation into the incidents and said it would continue to work with the CHRB and others to promote safety in California horseracing.

“We are all committed to the same thing—the highest level of equine safety and welfare—and we will continue to do everything possible to promote equine and rider health and safety.” the Stronach statement said.

Peterson praised the Stronach response.

“Now I think we see a commitment to be a leader in racing worldwide,” he said.

Meanwhile, Marty Irby, executive director of the equine advocacy group Animal Wellness Action, said the report underscores that reform is key to the future of horseracing nationwide.

“It’s time for an intervention,” Irby said, “and Congress must soon pass the Horseracing Integrity Act to reform the industry, or the public sentiment will continue to shift to eliminating horseracing itself.”


Pat Raia is a veteran journalist who enjoys covering equine welfare, industry, and news. In her spare time, she enjoys riding her Tennessee Walking Horse, Sonny.

Recipes for Success: Formulating Equine Diets

Does your horse need a dollop, dab, pinch, or peck? Learn to formulate a diet based on your horse’s age, body condition, and health status in this excerpt from the December 2019 issue of The Horse.

Recipes for Success: Formulating Equine Diets

Does your horse need a dollop, dab, pinch, or peck? Learn to formulate a diet based on age, body condition, and health status

Whether your adult horse is an average Joe, an easy or hard keeper, an athlete, a golden oldie, or has an underlying medical condition that requires a special diet, he has certain nutrient needs and calorie requirements you must factor into his daily rations.

“Diet is the foundation of equine health and welfare,” says Kathleen Crandell, PhD, a nutritionist with Kentucky Equine Research in Versailles. “This holds especially true now more than ever, considering the recent explosion of equine obesity and other nutrition-related diseases.”

In this article we’ll provide practical recipes for adult horses at various life stages and with specific medical conditions.

Even the best chefs in the world, however, can’t please every palate. You’ll likely need to fine-tune your horse’s diet based on his particular needs and preferences.

Maintenance Diet

Forage Feed 1.5-2% of body weight (BW) on a dry matter basis (including pasture or hay/haylage) per 24 hours. This is equivalent to 15-20 pounds of dried forage each day for a 1,000-pound horse.
Salt Offer a salt block (not a red mineral block) or top-dress feed with 1-2 tablespoons of table salt per day.
Water Provide ad-lib.


A maintenance diet is one that provides all the essential nutrients (vitamins, minerals, protein, fat, carbohydrates, etc.) a horse needs to maintain a healthy body weight. The maintenance diet is suitable for many pleasure horses without medical conditions, including horses in light work.

If your horse’s forage source is primarily hay, with minimal pasture, it becomes particularly important to weigh your hay rather than simply counting flakes.

“The National Research Council and recent research have shown that our modern-day forages are low in some essential nutrients,” says Crandell. “This is why equine nutritionists often promote a ration balancer or vitamin/mineral supplement for horses on pasture or hay alone.”

A ration balancer is designed to provide horses with all the nutrients they need that aren’t already met by quality forage.

You can easily modify this maintenance diet to meet the needs of easy keepers, defined as horses that easily maintain a body condition score (BCS) of 5-6 on the nine-point Henneke scale (TheHorse.com/137703). The major difference is you’ll need to restrict the number of calories they consume. Try decreasing the forage you feed to 1.4-1.7% of BW for easy keepers, and monitor body weight and BCS routinely to avoid obesity. In addition, consider adding more exercise. Several studies show that a combination of diet restriction and exercise achieves better results than instituting either change alone.

Hard Keepers

Forage Start by providing the maximal amount of high-quality forage. You can offer as much as 2.5% of BW in forage on a dry matter basis per day, some of which can be alfalfa. Replacing regular hay with 5-6 pounds of alfalfa can provide approximately 1,500 more calories per day.
Concentrate If your horse needs more calories than alfalfa alone can provide, add a concentrate. Start with a lower-starch concentrate rich in super fibers.
Fat To add calorie-laden fat, top-dress the concentrate with about ¼ cup of vegetable oil at each meal. Increase this amount to 1-2 cups at most over two to three weeks to allow the gastrointestinal tract to adjust.
Salt Offer a salt block or top-dress feed.
Water Provide ad-lib.


Hard keepers have difficulty maintaining a body condition of 5-6. They require additional calories either in the form of more forage, concentrates, and/or fat than that of the basic maintenance diet.

Performance Horses

Forage Offer 2-2.5% of BW in forage on a dry matter basis. High-quality hay and super fibers such as beet pulp and soy hulls ferment more efficiently in the large colon to produce energy.
Concentrate For additional calories that forage alone can’t provide, offer concentrate feeds specially formulated for performance horses.
Fat If your horse needs even more calories, offer vegetable oil (as described for hard keepers).
Salt Offer a salt block or top-dress feed.
Water Provide ad-lib.


Performance horses, like hard keepers, require extra calories to maintain appropriate condition. First, though, you need to be certain your horse is actually in heavy work before offering a high-calorie diet.

“According to the National Research Council’s Nutrient Requirements of Horses, examples of horses in heavy work include those involved in ranch work, polo ponies and show horses, low- to medium-level eventers, and horses in race training,” Crandell says. “These horses exercise about four to five hours per week with an approximate breakdown of 20% walking, 50% trotting, and 15% each of cantering, galloping, or other skills training.”

Performance horses require approximately 25% more calories than the basic maintenance diet provides. Further, be certain to include starch in performance horses’ diets to ensure they have enough energy and stamina for their jobs.

As an aside, says Crandell, “always add concentrates to the horse’s diet slowly at a maximum of 5 pounds per feeding or a maximum of 1.5% BW per day. Spread the concentrate out over several feedings rather than the traditional meals at breakfast and dinnertime.”

The Horse December 2019​This article continues in the December 2019 issue of The Horse: Your Guide to Equine Health Care. Subscribe now and get an immediate download of this issueincluding this in-depth article on on formulating your horse’s diet based on his age, body condition, and health status.

Already a magazine subscriber? Digital subscribers can access their December issue here. Domestic print subscribers who have not received their copy should email circulation@thehorse.com.


Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she’s worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.