Farm-Wise Equine Parasite Control Strategies

Each horse has his own individual needs when it comes to parasite control. But when you’re responsible for deworming a number of horses on one property, how do you meet each one’s needs?
Farm-Wise Equine Parasite Control Strategies

When you’ve got a barn full of horses with different parasite burdens, fecal egg count testing can help you deworm each one properly

Change can be hard, especially for horse owners. We follow the seemingly indisputable rules of horse care and management that have been handed down to us from generations past. And we can be taken aback when someone dares question our decades-old practices.

One tradition that must be bucked, however, is deworming horses at regular intervals. Blanket parasite control strategies have led to widespread drug resistance in many parasite populations. And if farm and boarding barn owners don’t transition to a more targeted approach, then the resistance of all parasite populations to all drugs on the market could very soon become a reality.

Each horse has his own individual needs when it comes to parasite control. But when you’re responsible for deworming a number of horses on one property, how do you meet each one’s needs? The answer lies in collecting a fecal sample prior to deworming and calculating the number of parasite eggs within it.

“There’s really no way to build a parasite control program without using fecal egg counts (FEC),” says Martin Nielsen, DVM, PhD, Dipl. ACVM, associate professor of parasitology at the University of Kentucky’s Maxwell H. Gluck Equine Research Center, in Lexington. Nielsen is one of the foremost experts in the field of equine parasitology and chair of the American Association of Equine Practitioners (AAEP) Parasite Control Guidelines ( committee.

Horse owners that don’t use egg counts can have a false sense of security; they might assume the anthelmintic (deworming) products they are using are working when, in reality, they have no way of knowing. “I feel like I spend all my time advocating for this, but these habits are slow to change,” he says.

Fecal Egg Count Cheat Sheet

John Haffner, DVM, associate professor at Middle Tennessee State University’s School of Agribusiness and ­Agriscience, in Murfreesboro, oversees the deworming program for the university’s 50-horse herd. “When I started practice years ago, we dewormed every horse as often as we could,” he says. “Some horses got wormed monthly. It may have been necessary back then, but with the advent of (the anthelmintic) ivermectin and the decline of large strongyles, it doesn’t make sense to deworm horses like that anymore. All horses aren’t suffering from heavy parasite burdens.”

“It’s not just that you might be spending money on a drug that isn’t working, but with a (parasite) population that is resistant to that class of drug, you can actually increase the intensity of resistance in that population by using a drug that doesn’t work anymore,” says Craig Reinemeyer, DVM, PhD, president of East Tennessee Clinical Research Inc., in Rockwood, and another leading equine parasitology expert.

So, with these veterinarians’ help, let’s find out how to craft an appropriate deworming program for every horse in your barn.

It’s All About Resistance

Horse owners currently use three drug classes to fight parasites: benzimidazoles (e.g., fenbendazole and oxibendazole), pyrimidines (pyrantel salts such as pyrantel pamoate and pyrantel tartrate), and macrocyclic lactones (e.g., ivermectin and moxidectin alone or combined with praziquantel).

These drugs’ efficacy, which Reinemeyer says was at least 95% when they were first approved, has changed over the past few decades.

“There’s no big broad-spectrum, ­umbrella-type product anymore that we can just give and know it gets everything in the horse,” says Nielsen. “There’s also not any product that we can just discard and kick out and never use anymore. Each of the products currently available has some resistance issues in some equine parasites, but each of them still has a use for some parasites infecting horses.”

For instance, Nielsen says, small strongyles (cyathostomins, the parasite of most concern in adult horses) show widespread resistance against all benzimidazoles and pyrantel salts and the beginnings of resistance against the macrocyclic lactones. In fact, he says he’d be surprised to find a farm that doesn’t have resistance issues against those first two drug classes.

In many places, moxidectin and ivermectin only suppress strongyle egg production (by paralyzing and killing internal parasites) for three to five weeks before counts return to pretreatment levels, he says. This is in contrast to the typical egg reappearance periods we used to see of three months for moxidectin and six to eight weeks for ivermectin. 

Reinemeyer adds that veterinarians are finding ivermectin resistance in most ascarid (roundworm, which is prevalent in foals) and some pinworm populations in the United States. And we might also start seeing more widespread ascarid resistance to the pyrantel salts, he says.

These resistance issues concern Nielsen because they’re only likely to increase in all drug classes. “Even the cheapest dewormer becomes expensive if it doesn’t work at all,” he says. And wasted money is one thing; the health risk that you’re running with your horses is another.

While Nielsen and others have been working to develop new anthelmintic products (read about these at, they’re not out of the research phase yet.

Developing a Strategy

The goal of any parasite control program, says Nielsen, is to reduce the level of egg shedding in your herd to, in turn, reduce pasture contamination and parasite infection. Before developing a deworming strategy for your farm, consider your area’s active grazing season and the age of each horse.

Then measure each horse’s fecal egg count to determine his shedding status. Low shedders pass no more than 200 eggs per gram of feces; moderate ­shedders pass 200-500 eggs per gram; and high shedders pass 500 or more eggs per gram, says Reinemeyer. This is crucial to know, he explains, because only 20% of your horse population passes about 80% of all parasite eggs on your property. Once you’ve tested a mature horse several times to determine his shedding status, his classification is unlikely to change.

Elizabeth Houtsma and her husband, Greg Houtsma, DVM, own Hillside H Ranch, a small Warmblood breeding farm in Warrensburg, Missouri, as well as Midwest Performance Equine and Warrensburg Animal Hospital. They switched from a traditional rotational dewormer schedule and began using FEC testing in 2005 due to parasite resistance concerns.

“Because of our fecal egg count testing, we’ve been able to determine which horses are high shedders and which horses are not,” says Elizabeth Houtsma, adding that she and her husband test any horse new to their property before deworming, after deworming, and periodically through the first year to determine its shedding level. They only test longtime residents once a year or every other year, unless they suspect a ­problem. They test horses under 2 and seniors more frequently.

For adult horses in your herd, perform FECs during your region’s active grazing period—typically once in the spring and again in the fall after worms have ­accumulated all year—and deworm as needed.

Juvenile horses require an alternate approach, says Nielsen, because foals, yearlings, and young horses have different parasites and higher burdens and are more susceptible to disease. “It’s like two different species of animals,” he says, adding that a young horse’s age is particularly important; as his immune system develops, it’s better equipped to eradicate parasites.

Around four to six months of age, horses’ immune systems develop to a point they’re able to kick out the ascarids; this is when strongyles start increasing in number, says Nielsen. Fecal egg counts at weaning time can help reveal if a young horse has reached this point, and what type of parasites he has, so you can administer the appropriate dewormer.

Horses that are being transported, competing, or in training tend to have higher egg counts, but not necessarily due to higher parasite burdens, says Nielsen. More likely, these horses have weaker immune responses due to stress, which allows the parasites they already have to produce more eggs. Therefore, run FECs on any transient horse or horse in training at least twice a year. If one becomes a high shedder, you can change his treatment regimen.

“It’s just nice to make sure you get those horses treated so they’re not shedding and contaminating the environment everywhere they go and after they come home,” says Nielsen.

Older horses and those with pituitary pars intermedia dysfunction (PPID or equine Cushing’s disease), equine metabolic syndrome, or that are immunocompromised also have special parasite control needs. Researchers have shown that horses over 20 are significantly more likely to have high egg counts than middle-aged horses. Elizabeth Houstma says she’s seen this in her own population of mares: The geriatric ones are typically high ­shedders.

Nielsen says these horses might need an additional treatment a month to six weeks after the initial one because eggs might start reappearing sooner.

Deworming Tips

As we’ve discussed, a horse’s shedding status dictates how frequently he should be dewormed. However, our sources say adult horses, regardless of fecal egg count, should be dewormed once or twice a year, usually in the spring and fall, to help eradicate small strongyles, tapeworms, and sometimes pinworms—the three worm species of most concern for adult horses.

If you experience winter where you live, you won’t need to deworm during that season because the cold prevents parasites from developing into an infective stage, says Nielsen.

Because FECs only identify small strongyle and ascarid burdens, owners should administer a dewormer against tapeworms (e.g., praziquantel or pyrantel pamoate) at least once a year to control them. If you notice bot eggs on horses’ legs or around their manes, you can administer an effective drug class (ivermectin and moxidectin) to help prevent the larvae from making their way into the horse’s mouth and gastrointestinal tract. 

Testing Your Anthelmintics

To evaluate the efficacy of a drug class on your property, also be sure to perform fecal egg count reduction tests (there’s an acronym for that, too: FECRT). Have your veterinarian perform an FEC on each horse before treatment, deworm that horse as necessary, test a subsequent fecal sample from the same animal roughly 10 to 14 days later, and compare the two.

“You need to do it for every group of horses or class of anthelmintic that you use on the farm,” says Reinemeyer. “You should get at least a 98% reduction of egg counts post-treatment with ivermectin and moxidectin and at least 90% with the other dewormers. If you’re not getting that now, then it means that the worms have changed. If you demonstrate that a particular class is worthless on your farm, you should never use it again,” for routine deworming. That drug, however, might still be useful against other parasites.

For those drug classes that are effective, recheck them about every two years, he adds.

Not all horses need an FECRT. You can determine a product’s efficacy by testing about six horses in a herd that are known to have moderate to high egg counts, says Nielsen. If results come back showing any positives, the parasites on your property are resistant to that product.

Take-Home Message

Thanks to current widespread drug resistance in many parasite populations, it’s important for horse owners to understand that each horse has individual deworming needs. Those needs depend on the horse’s parasite shedding status and the farm’s drug resistance status, both of which can be determined using fecal egg counts.

To develop a parasite control program for your farm, review the AAEP’s guidelines and talk to your veterinarian. Our sources agree that all facility managers and farm owners should adopt these protocols to avoid ending up with a world in which equine parasites are ­uncontrollable.

Do Snorts Suggest Horses are Happy?

New evidence suggesting that horses produce more snorts in favorable situations could improve animal welfare practices, researchers say.
Snorts suggest horses are happy

New evidence suggesting that horses reliably produce more snorts in favorable situations could help improve animal welfare practices, according to a recently published study by Mathilde Stomp, PhD, and colleagues from the Université de Rennes, in France.

Assessing positive emotions is important for improving animal welfare, but it has been challenging to identify reliable indicators. Physiological markers often give contradictory results, and many behavioral signals can be ambiguous. In particular, few studies have examined acoustic indicators of positive emotions.

Anecdotal reports have indicated that horses frequently produce snorts in positive situations. So Stomp and colleagues evaluated how frequently 48 horses—which lived either in restricted conditions (i.e., riding school horses that spent much of their time in individual stalls) or naturalistic conditions (i.e., stable groups of horses always in pasture)—snorted.

The researchers found that snort production was significantly associated with positive situations and with a positive internal state, as indicated by ears positioned forward or sideways. For example, riding school horses produced twice as many snorts in pasture than when they were in stalls. Further, they found that horses living in natural conditions emitted significantly more snorts than riding school horses in comparable contexts. Taken together, the findings suggest that snorts are reliable indicators of positive emotions in horses, the team said.

“The snort, a nonvocal signal produced by the air expiration through the nostrils, is associated with more positive contexts (in pasture, while feeding) and states (with ears on forward position) in horses,” Stomp said. “Moreover, it is less frequent in horses showing an altered welfare. These results provide a potential important tool as snorts appear as a possible reliable indicator of positive emotions which could help identify situations appreciated by horses.”

The study, “An unexpected acoustic indicator of positive emotions in horses,” was published in PLOS ONE.

Transporting Horses Post-Joint Injection

Transporting Horses Post-Joint Injection

Q: I ship my mare to a clinic for her joint injections. How long do I need to wait after sedation and the injections before putting her back on the trailer and taking her home?

Sean, Maryland

A: You can ship immediately after joint injections as long as the horse is stable while standing still. Traveling will not cause harm to the newly injected joints. Veterinarians use different doses of various medications, depending on personal preference, but if your mare is very wobbly and could fall when you turn a corner, you might want to wait about 30 minutes after the injections. Generally, if she can walk and load easily, she can ship. It is fine for her to ship mildly sedated; however, you might want to pull her hay so she doesn’t choke. If the joints that were injected are on the lower limbs, you could also ask your vet to apply bandages to protect them from trauma and contamination during the journey.

Journey Through the Equine GI Tract

Learn about special characteristics of each part of the horse’s digestive tract and different medical conditions that can develop there
Journey Through the Equine GI Tract

Follow fodder’s fate through a horse’s digestive tract

When someone mentions the equine gastrointestinal (GI) tract, what do you think of first? Maybe you immediately picture the abdomen, where the bulk of this body system lies, moving ingesta along through its twists and turns of intestine. Or, your mind might roam to the mouth, responsible for consuming the forages, concentrates, and supplements you have worked hard to source. Conversely, you consider the hind end, producer of the mounds of manure you spend hours mucking, picking, and transporting from one place to another. 

Unlike some organ systems, the GI tract changes immensely from one section to the next, with each segment aimed at one specific goal: providing energy (calories) for the horse’s body. In this article we’ll explain how each part of the equine GI tract is designed to break down plant products to produce energy. We’ll also describe each region’s special characteristics and the medical conditions that can develop there. Note that all measurements included here refer to an average 500-kg (1,100-lb) horse.

Head First

Horses use their lips to painstakingly procure food, sifting through this plant and that to pick the perfect stem or leaf with their lips and incisors to deliver to the oral cavity. Once the plant or feed is within the mouth, enzymes in the saliva begin to break down its tough cell walls while simultaneously wetting and lubricating it for the upcoming voyage. The molars and premolars also assist by physically breaking down the plants to create a moist, semidegraded food bolus the horse then swallows.

Health Risks

  • Dentition Because teeth play such an integral role in preparing forages for the remainder of the digestion process, be sure to have them examined at least annually. Don’t wait for quidding (when horses drop chunks of partially chewed feedstuffs) or weight loss to develop before having the veterinarian out.
  • Salivary gland issues Although rare, several conditions can impair the salivary glands. Foreign bodies, such as awns from plants, can puncture the glands or ducts or block saliva flow. Salivary stones (sialoliths) can develop in the glands or ducts, also blocking flow. Head trauma can damage ducts, and tumors such as melanomas and sarcomas can develop there. Infections of the glands and ducts can also occur, most notably due to the rabies virus and the bacterium Streptococcus equi that causes strangles.
  • Temporomandibular joint (TMJ) problems Some horses develop pain or arthritis in this joint at the junction of the upper and lower jaws, which can negatively impact mastication (chewing).

Down the Hatch

Once the horse swallows the neatly packaged food bolus, it travels down the length of the muscular, tubelike esophagus, which begins at the epiglottis at the back of the oral cavity near the larynx. The esophagus simply serves as a conduit to funnel food from mouth to stomach. Peristalsis—regular, rhythmic muscular contractions—propel the food in a timely manner. No further feedstuff breakdown occurs here because the esophagus is largely devoid of salivary glands, but it does house mucous glands that help lubricate the potentially rough food bolus as it travels. When the bolus reaches the end of the esophagus, it pops through the muscular ring between the esophagus and stomach known as the esophageal sphincter. 

Health Risks

  • Choke An esophageal obstruction can cause discomfort, excessive drooling, lethargy, and malaise, as well as more serious long-term complications. For instance, a bolus of food stuck in the esophagus can damage the esophageal lining. As a result, scars can develop, causing the esophagus to contract, or a rent can form (a tear that causes diverticulitis).
Journey Through the Equine GI Tract

The Bulky, Brawny Abdomen


Once dispelled from the esophagus, the food bolus hits the stomach. The equine stomach only holds 8-15 liters (picture eight milk cartons), accounting for a mere 9% of the GI tract. Alternatively, the human stomach makes up about 17% and typically holds about 1 liter, though it can expand to hold up to 4.

Veterinarians estimate it takes only 12 minutes for food to move through the stomach, which explains how horses can graze for so many hours each day (approximately 17 hours in a 24-hour period with free access to pasture). The hydrochloric acid produced in the stomach’s glandular region (the lower half) breaks the food bolus down into small pieces. In addition, some enzymes begin the actual digestion process.

Digestion involves breaking down protein and simple water-soluble (also known as nonstructural) carbohydrates into amino acids and individual sugar molecules, respectively.

Once the small, partially digested pieces of food pass from the stomach into the small intestine (not to be confused with the small colon we’ll discuss later), things start to get interesting. Much like a marble run game, the partially digested feed materials course through the abdomen, twisting and turning through coiled loops of intestine.

The first section of small intestine is called the duodenum. Enzymes released into it continue the digestion process initiated in the oral cavity and stomach. Thanks again to peristalsis, partially digested food travels along the duodenum before passing seamlessly into the longest section of the small intestine, the jejunum. Here, enzymatic digestion of feedstuffs continues to produce additional amino acids and sugars and other nutrients that are absorbed in the latter regions of the jejunum. The ileum, the third and final section of the small intestine, also helps absorb digested nutrients.

The entire trip down the 22-meter-long (60-65-foot) small intestine is remarkably fast—up to 0.3 meters (1 foot) per minute. Compare this to the human small intestine, which measures 6 meters (10 feet) and moves at a rate of about 0.04 meters per minute (0.13 feet).


Most feedstuffs are composed of structural carbohydrates that cannot be digested efficiently and must instead be fermented. To review, digestion requires enzymes to break down feed and produce amino acids and simple sugars, along with small fat particles. Fermentation, on the other hand, uses microorganisms such as bacteria, fungi (including yeast), and protozoa to break down feed materials. The process produces volatile fatty acids (VFAs, such as butyric and acetic acid) that are absorbed into the bloodstream and used to fulfill most of the horse’s energy requirements. Fermentation provides far more energy to horses than does digestion, which is the opposite of what happens in humans. This explains why horses fall into the “hindgut fermenter” category, along with rhinos and rabbits.

The collection of microorganisms responsible for fermentation is referred to as the hindgut’s microbiome. Research into this microbiome continues at a furious rate, and an improved understanding of it has the potential to maximize horse health from the inside out, says Shannon Pratt Phillips, MSc, PhD, an associate professor in North Carolina State University’s Department of Animal Science.

The cecum and large intestine make up the bulk of the GI tract and contain millions of these microbes that ferment food materials to produce VFAs. The voluminous cecum serves as the gateway to the large intestine. It has a capacity of approximately 30 liters—almost triple what the stomach can hold. The food bolus of undigestible but fermentable material passes from the ileum through a tiny hole, or ileocecal orifice, into the cecum where fermentation begins. Essentially, the cecum is a muscular sac, equivalent to a human’s tiny 3-4-cm appendix that serves as a venue for initiating fermentation. After about seven hours of fermentation, feed passes into the large intestine for additional fermentation.

The 12-foot-long large intestine (often referred to as the large colon), although relatively short compared to the small intestine, boasts an impressive volume—a whopping 75 liters (20 gallons). This is equivalent to the amount of fuel required to fill a minivan’s or large SUV’s gas tank. From the cecum, the large intestine becomes somewhat of a whirling dervish, yet still not as circuitous as the looping small intestine. The large intestine courses up the right side of the abdomen toward the diaphragm, which separates the thoracic (which contains the lungs) and abdominal cavities, before turning left and traveling down the left side of the abdominal wall. These two sections of the large intestine are referred to as the right and left ventral colons, respectively. Next, the large intestine doubles back on itself in the pelvic region, at a location referred to as the pelvic flexure, and becomes markedly narrower. The left dorsal colon continues back toward the diaphragm, becoming the right dorsal colon before crossing into the middle of the abdomen as the transverse colon and finally racing toward the rectum.

“In my opinion, the cecum/large colon is the most delicate part of the GI tract,” says Pratt Phillips. “It is a wonder of evolutionary development to suit what horses were consuming throughout history compared to ruminant species, for example. But it also causes issues in modern horses with its twists and turns and changing diameters.”

Health Risks

Entire textbooks are devoted to the list of things that can go wrong in this part of the horse’s body. The intestinal tract’s massive length, volume, and continual change in diameter and direction beg for disaster at every section.   

  • Gastric ulcers Almost all performance horses and even some pleasure horses suffer from painful ulcers caused by splashing hydrochloric acid in the stomach’s squamous and glandular regions.
  • Colic A fancy way of saying abdominal pain, colic can strike at any time. As you can guess from the seemingly haphazard way that the intestines appear stuffed in the equine abdomen and their sudden changes in size, especially in the large intestine, blockages and twists aren’t uncommon.
  • Internal parasites Roundworm (asacarid) and small strongyle (cyathostomin) infections can occur in adult horses, with the latter being the most concerning. A less common but more serious condition is larval cyathostominosis, caused by mass eruption of encysted larvae.
  • Diarrhea A potentially life-threatening condition, diarrhea has a variety of causes, including bacterial infections, such as Clostridium difficile or Salmonella spp, and diet changes.
  • Hindgut acidosisA sudden decrease in pH—often tied to large amounts of rich concentrate feeds—can make the large intestine’s contents more acidic than normal. This will alter the population of microorganisms in the large intestine, interfering with fermentation and potentially causing ulceration of the lining of the cecum and large intestine, as well as diarrhea.

The Final Few Feet

The small colon descends from the transverse colon, terminating at the rectum and anus. Here, fecal balls form, and excess water is absorbed before manure is expelled. Thankfully, once we reach this portion of the GI tract, we are home free, with few worries.

Health Risks

  • Melanomas These tumors can develop in the horse’s anal region. In some cases, melanomas grow so large as to block manure passage. Gray horses are particularly susceptible, with approximately 80% affected.

Take-Home Message

Having a clear understanding of equine GI tract structure and function maximizes an owner’s ability to recognize the wide array of digestive conditions that can threaten horse health. For anyone who has suffered through the roller coaster of colic or battled with gastric ulcers, chronic choke, hindgut acidosis, and more, the balance between GI clockwork and ticking time bomb is tenuous. Assess horses daily, maintain a consistent forage-based diet, integrate feed changes slowly to allow the microorganisms in the fermentation vat to adapt to those alterations, and consult a veterinarian immediately if you discover any abnormality.

“Horses should have plenty of forage in front of them at all times, unless they are overweight,” says Pratt Phillips. “The fiber within helps keep food moving through the gut and helps maintain the microbial ecosystem.”

About The Author


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.

4 Misconceptions About Alfalfa

Does alfalfa cause kidney or respiratory problems or make horses hyper? Specialists shed light on these myths and more.

Despite all the science-backed suggestions about feeding alfalfa, it remains a misunderstood forage. The following are a few misconceptions worth clarifying.

Myth: An alfalfa-rich diet causes kidney problems.

“A normal, healthy horse can metabolize and excrete the extra protein in alfalfa just fine, if the horse has adequate water,” says Ray Smith, PhD, forage extension specialist at the University of Kentucky, in Lexington. Horses with kidney disease shouldn’t consume a high-protein diet (such as alfalfa), but the alfalfa itself won’t cause kidney disease.

Myth: Alfalfa makes horses hyper.

“I don’t think there is any scientific basis for this,” says Krishona Martinson, PhD, associate professor and equine extension specialist at the University of Minnesota’s Department of Animal Science, in Falcon Heights. “Alfalfa does have more energy compared to grass hay of similar maturity, so perhaps a horse eating a lot of alfalfa in the absence of exercise may have more energy. The biggest issue with alfalfa, however, is weight gain in horses that don’t have adequate exercise.”

Myth: Alfalfa has high nonstructural carbohydrate (NSC) levels.

“Cool-season grasses like timothy, bromegrass, and orchardgrass actually have higher nonstructural carbohydrate content and sugars than legumes,” says Martinson. “Horses with carbohydrate sensitivity (e.g., obese horses, those with laminitis, equine metabolic syndrome, equine Cushing’s disease, or polysaccharide storage myopathy) need their diet carefully monitored for nonstructural carbohydrates and can benefit from including some alfalfa rather than grain or cool-season grasses.”

Myth: Alfalfa aggravates respiratory problems in horses with heaves.

Some horses tend to cough more when fed alfalfa, but this is due to irritants such as dust and mold rather than the alfalfa itself. Alfalfa can be dustier than grass hay when moisture conditions at baling are less-than-ideal. Alfalfa leaves also tend to shatter when too dry, creating more dust particles.

“Mold formation is also related to moisture content when baling,” says Martinson. “One issue with alfalfa—which tends to have more stem than grass—is that the stem takes longer to dry. Alfalfa might take 12 to 24 hours longer to dry than a grass crop, simply because it has more stems. Moldy grass hay or moldy alfalfa hay both cause airway irritation when mold dust is inhaled.”

Take-Home Message

The horse industry is full of misconceptions about alfalfa. Before dismissing this nutrient-rich forage, contact your veterinarian or equine nutritionist to develop a feeding program that’s right for your horse.

About The Author


Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey’s Guide to Raising Horses and Storey’s Guide to Training Horses. Besides having her own blog,, she writes a biweekly blog at that comes out on Tuesdays.

Protein and Equine Ration Balancers: Let’s Do the Math

Nutritionist Dr. Clair Thunes explains why ration-balancer protein contents might seem high but aren’t.
Equine Ration Balancers

Q. I have been reading several of your commentaries and see that you recommend feeding equine ration balancers on predominantly forage diets. When I looked at ration balancers at my feed store I notice that they tend to be high in protein, often around 30%. Isn’t that too much protein? I thought mature horses only need about 10-12% protein in their diet. What am I missing?

Via e-mail

A. This is a question I get asked quite often, and at first glance you are quite right. But if we delve a bit deeper I think you will see why the ration balancer doesn’t, in fact, offer too much protein.

Most equine ration balancers have a recommended daily intake of 1-2 pounds (0.45 to 0.9 kilograms) per day. Where the crude protein content is 30% this means that 0.3 pounds (136 grams) of protein are supplied when feeding a pound and 0.6 pounds (273 g) of protein if feeding two pounds.

Let’s say that your horse weighs 1,100 pounds (500 kilograms) and that you feed an average grass hay with a crude protein of 11% at a rate of 2% of body weight per day. This equates to 22 pounds (10 kilograms) of hay that provides 2.42 pounds (1.1 kg) of protein (we reach this number by multiplying 22 pounds by 0.11 [which represents 11%] for the protein content). As you can see the hay is providing far more protein than the ration balancer. The ration balancer has a high protein content but a small serving size so its total contribution is small.

If we assume that this horse is in moderate work, per National Research Council guidelines, he needs 768 grams (or 0.768 kilograms) of protein a day. To convert this to pounds we multiply the amount in kilos by 2.2, because there are 2.2 pounds to a kilo. This gives us a daily protein requirement of 1.69 pounds. In this example the hay is meeting the horse’s protein requirement; however, if the horse was fed less than 2% of body weight per day because he’s an easy keeper, his requirement might not be being met. Similarly, if the hay actually had a lower crude protein content or the horse was in heavier work, the same might also be true.

Considering Easy Keepers

Sometimes I see easy keepers being fed lower nutritional quality hays at lower amounts to reduce calorie intake. For example, a stemmy grass hay with a crude protein of 8% fed at 1.5% of this horse’s body weight would yield only 1.32 pounds (0.6 kilograms) of protein, which is not enough to meet requirement. Adding 1.5 pounds (0.68 kilograms) of ration balancer with 0.45 pounds (0.2 kilograms) of protein would bring the ration protein intake to 1.77 pounds (0.8 kilograms) of protein, which meets his requirement.

Beyond just meeting requirement there is the issue of protein quality and even a grass hay that provides adequate crude protein might lack adequate levels of some essential amino acids. Or the protein might not be fully available if bound up with indigestible structural carbohydrates. Equine ration balancers not only provide crude protein, they tend to provide guaranteed levels of the most limiting essential amino acids, such as lysine and methionine, that are vital for your horse’s health. So, they’re a good insurance policy even if on paper it looks like protein intake from the forage should be adequate.

Equine Ration Balancers vs. Performance Feeds

Another comparison I often see people make is between ration balancers and performance feeds. Most performance feeds have crude protein levels around 12% and a daily recommended intake upwards of 5 pounds per day. At 5 pounds (2.25 kilograms) per day this would provide 0.6 pounds (0.27 kilograms) of protein (5 x 0.12) the same as two pounds of the 30% ration balancer. In fact, performance feeds given at the upper ends of the recommended feeding levels provide far more protein a day than the ration balancer, even though the previous only contain only 12% protein.

The Alfalfa Exception

There are times when you might not want or need the additional protein coming from a 30% ration balancer, and one of these is if you are feeding a lot of alfalfa. Alfalfa provides considerably more protein than required and also tends to have a slightly better amino acid profile than grass hay, so you might decide the protein in the ration balancer is unwarranted. I tend to find that horses   fed 25-30% of their forage ration as alfalfa do just fine on the high-protein ration balancer; however, you might have other options.

A few companies make ration balancers specifically for horses being fed alfalfa and these have a protein content of around 12%. They still guarantee the necessary essential amino acid levels but do so without feeding unnecessary crude protein. They also have lower calcium, because alfalfa provides considerable calcium to the ration.

Take-Home Message

When comparing the protein contents of feeds at your feed store do not take the crude protein contents on face value. Make sure you understand the feeding directions and then consider the role of that feed within your horse’s total daily ration. You will likely find that the high-protein ration balancer is not contributing as much protein as you might at first think.

About The Author


Clair Thunes, PhD, is an independent equine nutrition consultant who owns Summit Equine Nutrition, based in Sacramento, California. She works with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses. 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 United Kingdom Pony Club. Today, she serves as the regional supervisor for the Sierra Pacific region of the United States Pony Clubs. As a nutritionist she works with all horses, from WEG competitors to Miniature Donkeys and everything in between.


Hormone Treatment Gets Mares Ready to Breed Rapidly

Mares receiving the synthetic hormone reFSH went from anestrus (not cycling) to ready to breed within about a week, researchers found in a recent study.
reFSH for horse breeding

Artificial lighting during the winter might get your mare cycling sooner for early breeding, but it won’t happen overnight. However, scientists testing a new hormone treatment have found that it leads to similar results and good pregnancy rates in a fraction of the time.

Mares receiving a synthetic hormone called recombinant equine FSH (reFSH) went from anestrus (not cycling) to ready to breed within about a week, researchers from the University of California, Davis (UC Davis), found in a recent study.

“Mares that were in deep anestrus, without lights, responded to reFSH by developing ovulatory follicles and ovulating after treatment with an ovulatory agent,” said Janet F. Roser, MS, PhD, professor emerita in the UC Davis Department of Animal Science. “There is no second guessing as to when the mares will respond, which allows for timed breedings and less monitoring compared to when mares are under lights.”

In their study, Roser and her fellow researchers administered reFSH intramuscularly to 20 mares in deep anestrus twice a day, every day, until their follicles reached 35 millimeters in diameter, which took five to seven days in the study mares.

Once the follicle was mature, the researchers induced egg release with a second hormone (hCG) and bred the mare through artificial insemination. They found that 80% of the mares conceived, and 70% were still pregnant by Day 24 when a fetal heartbeat was observed by transrectal ultrasonography.

Interestingly, Roser said, all the mares continued to cycle spontaneously after the researchers induced abortion at Day 25. This indicates that the treatment has lasting effects on the cycling process and probably doesn’t need to be used more than once in a breeding season.

reFSH for horse breeding

She said using reFSH is less labor-intensive, not to mention much quicker, than applying lights every day.

“It takes 60 to 90 days for mares to start cycling using artificial lights,” she said. “Breeders need to make sure that lights go on in the evening for about six hours to extend the daylight period and that the mares are close enough to the lights to respond. Generally mares are brought in from pasture or paddocks to stalls every day at the end of the day. Lights in paddocks don’t always work, as mares could stand in a corner or have their head hang over the fence.”

Keeping mares in the stalls at night also raises farm expenses through labor, bedding, and electricity costs, Roser said. It could also compromise horse welfare by reducing their daily pasture time and isolating them in box stalls. With reFSH treatment, mares don’t need to be stalled, she said, and can remain at pasture.

She cautioned that reFHS treatment can increase the risk of multiple ovulation and, therefore, multiple pregnancies. As such, she added, skilled veterinarians should follow these mares carefully after insemination to reduce twin pregnancies if they occur.

ReFSH might also be a useful treatment for mares that have stopped ovulating for medical reasons, such as granulosa cell tumors, Roser said. Once the medical problem has been resolved (through surgery, for example), mares sometimes stay in anestrus. Lights don’t help in medical cases like this. However, reFSH could stimulate the other ovary to start functioning again. Another application for reFSH in mares is to superovulate them to increase the number of embryos for embryo transfer.

ReFSH is produced in a laboratory but has similar properties and biological activity to natural FSH, Roser said. Researchers didn’t use the natural hormone in their studies, however, because they would have had to harvest it from deceased mares. A synthetic version would allow them to produce it as necessary, with hopes of having it ready for the commercial market in 2019 or 2020.

The study, “Deep anestrous mares under natural photoperiod treated with recombinant equine FSH (reFSH) and LH (reLH) have fertile ovulations and become pregnant,” was published in Theriogenology.

About The Author


Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor’s in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

Fixing Horse Splint Bone Fractures With Absorbable Screws

Researchers have learned that fractured splint bone healing can be optimized by replacing metal screws with absorbable ones.
fixing horse splint bone fractures

Fractures in the proximal (upper) third of splint bones, close to the knee, can be career-ending injuries without treatment, but even fixation with metal implants to hold the bone in place isn’t a surefire fix. Metal screws have issues of their own, sometimes hindering healing and interfering with future diagnostic imaging. Fortunately, though, veterinarians have a new treatment method at their disposal. A recent study has shown that fractured splint bone healing can be optimized by replacing metal screws with absorbable ones.

“Bioabsorbable screws appear significantly more biocompatible with the natural tissues than metallic screws,” said Mahmoud Mageed, DrMedVet, of Tierklinik Lüsche GmbH Equine Hospital, in Bakum‐Lüsche, Germany.

Another advantage, Mageed said, is that the horse’s body does, in fact, absorb the screw material. As a result, the screw would likely not need to be removed via a second surgery, as is often the case with metal screws.

Fractures of the upper third splint bone are rare, but usually occur as a result of an external traumatic injury (such as a kick). Depending on the fracture’s location along the splint bone, different management options are possible—including conservative management with rest and medications. Fractures occurring near the top of the bone, close to the knee, usually require surgery to repair. Surgeons use screws to stabilize the broken fragment or the remnant of the fragment after removing part of it.

But metal screws are often associated with infection at the surgery site, Mageed said. Plus, the metal interferes with diagnostic imaging, which veterinarians use to evaluate the status of the bone, along with nearby tendons and ligaments.

“It’s fairly common to see a splint bone fracture combined with an injury of the surrounding soft tissue,” he said. “The use of bioabsorbable screws doesn’t hinder investigations by MRI or CT scans.”

fixing horse splint bone fractures

In their study, Mageed and colleagues reviewed medical records involving eight horses treated in their hospital with bioabsorbable implant screws. All the horses had fractured their proximal splint bones and received the bioabsorbable implants to repair them. Some of the horses had been injured for several months, and some had already had surgery to partially remove the fragmented bone without screw fixation. Seven of the horses had mild lameness (1 or 2 out of 5), and one had moderate (4 out of 5) lameness.

After surgery, the horses followed a gradual exercise program of two weeks of hand-walking and four weeks of turnout. The researchers continued to observe the horses’ progress for up to 18 months after surgery.

None of the horses had surgical complications, Mageed said. Six of the horses had returned to full work three months after surgery. Two remained mildly lame; those were the horses that had had previous surgery already, which could have affected the later surgery’s outcome, he said.

At 12 months after the operation, the screws were visible in radiographs as lucent cone shapes, but they did not interfere with imaging, said Mageed.

Bioabsorbable screws are far more expensive than metal screws (about €300, or $350 per screw, in their clinic, compared to only €10, or about $12, for a metal screw), he said. However, their use would prevent the additional costs of a second surgery to remove a metal screw, if necessary.

While the study showed promise, it involved a small number of horses, Mageed said. As such, more research is needed before veterinarians recommend bioabsorbable screws.

The study, “Internal fixation of proximal fractures of the 2nd and 4th metacarpal and metatarsal bones using bioabsorbable screws,” was published in the Australian Veterinary Journal.

About The Author


Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor’s in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

Horse Hierarchy Test Doesn’t Always Agree With Pasture Pecking Order

The “bucket test” has its place but it can give significantly different results than an all-day field test of horses at pasture. That’s especially true for lower-ranking horses, researchers said.
Horse Hierarchy

You know your horse-feeding routine backward and forward and which horse will meet you at his bucket first or last. Jack always eats before Jenny, who eats before Andy, who eats before Sam. So you’ve got the dominance and the social design of your herd all worked out. Right?

Now try watching them at pasture all day. And think again.

Swiss researchers have learned that the “bucket test,” used to determine horse dominance, has its place, but it can give significantly different results than an all-day field test of horses at pasture. That’s especially true, they said, for the lower-ranking horses.

“We noted a rate of difference of 58% between a field observation test and a food dominance test in the hierarchy of our group of 12 study mares, with the greatest variations seen in the most dominated horses,” said Marie Roig-Pons, MSc candidate studying in association with Anja Zollinger, BSc, scientific collaborator the Agroscope national research center at the Swiss National Stud, in Avenches. Roig-Pons presented her group’s work at last year’s Swiss Equine Research Day.

“This leads us to question the reliability of the food dominance test method, especially for horses in the lowest ranks,” she said.

Horse Hierarchy

Roig-Pons and Zollinger tested 12 mares from the Swiss National Stud that already had an established social hierarchy and group stability. They first tested them by presenting a bucket of feed to two horses at a time until they’d tested all pairs, which gave the researchers a ranking order. They then observed the mares at pasture for 11 hours, taking note of all positive and negative interactions. They also recorded “nearest neighbors”—which horse stood closest to which—every 10 minutes of the 11-hour observation.

They found clear hierarchical structure in the pasture test, but it didn’t always agree with the ranking they found in the bucket test phase, Roig-Pons said.

They also recognized that many of the social interactions and actions weren’t necessarily related to hierarchy, she added.

“Our observations in the pasture revealed that the other behavioral parameters we observed, especially with regard to the level of aggression between individuals, their number of friendly interactions, and their nearest neighbor, cannot be explained by hierarchy status alone (regardless of the kind of test and calculation used),” Roig-Pons said. “Hierarchy is not the only way to describe social relationships within a group.”

Knowing a group’s hierarchy, and paying attention to it, can help owners and breeders create and/or maintain more harmonious groups, the researchers said.

This could not only reduce injury risk but also improve each individual horse’s welfare, they said.

About The Author


Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor’s in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

Training Aids: How Their Fit Could Help or Hinder Longeing Horses

Researchers know that, when used and fit properly, training aids can positively affect horses. However, improperly fitted equipment could squelch any benefits these systems offer.
horse training aids

Researchers know that, when used and fit properly, training aids, such as the Pessoa training aid, can be useful in longed horses and have positive effects. However, British researchers have confirmed that pressure from some training aids could prevent horses from improving their movement through these aids.

“Training aids are very useful for a variety of reasons, but the benefits of their use might be diluted when there are other pressures interfering,” said Russell Guire, a PhD candidate at the Royal Veterinary College, in London, and a researcher at Centaur Biomechanics in Warwickshire, both in the U.K. He presented his group’s study at the 2017 British Equine Veterinary Association Congress, held Sept. 13-16, in Liverpool.

In their study, Guire and his fellow researchers tested three training aids’ effects on 10 healthy, sound riding horses’ movement during longing. A single longer worked each horse in both directions, with four repetitions, each time fitted with either a surcingle (also called a training roller in the U.K.) alone or a training roller with a Pessoa system, a continual rope system, or side reins. The scientists equipped the horses with inertial measuring units to determine pelvic range of motion and movement symmetry during the tests.

Although the researchers found minor differences between the training aids compared to the training roller alone, there were no statistically significant differences in the studied movements at both trot and canter, Guire said.

So what does that mean for these aids’ use?

While science has already confirmed the usefulness of training aids like the Pessoa system and elastic bands, improperly fitted training rollers could be squelching any benefit these systems offer.

“We’ve noted significant pressure under the training roller that’s close to the pressure found during a sitting trot,” Guire said. “Most rollers don’t have trees, so when they’re tightened up, they put that pressure directly onto the horse’s spine at about the level of T12-T13 (thoracic vertebrae). We believe that this pressure could reduce any benefits the horse could have from the training aids.”

Previous studies by the same team have already indicated that pressure at T12-T13 inhibits locomotion, he added.

Their group is currently working on a study that should help give concrete recommendations about how to fit a training roller so as to let horses fully benefit from training aids on the longe, said Guire.

In the meantime, however, people can try longing with a training roller on top of the saddle or putting pads around the withers to ensure clearance under the training roller, he said.

The study, “Effect of Training Aids on Movement Symmetry, Pelvic Range of Motion and Rein Tension Pressures During Lunge Exercise,” was published in the Equine Veterinary Journal.

About The Author


Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor’s in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.