Search Our Website

By Nora Grenager , VMD Published in Bay Area Equestrian Network December 2007 Introduction Colic. To some, it is a term that is unfortunately all together too familiar; to others, it is a word that causes fear with little understanding of what it is. While it is a situation we would all like to avoid, it is important to have a knowledge of what colic is, some of its causes, potential ways to minimize its occurrence, and how your veterinarian may deal with it. Causes Approximately 4 to 6% of horses in the United States will suffer from colic each year. This is a difficult statistic to interpret, because many mild episodes of colic likely go unnoticed. Of that percentage, only a very small amount require surgery. “Colic” is just a term that encompasses any abdominal pain – it is a clinical sign, not a specific disease. Horses have very extensive gastrointestinal tracts, and there are numerous possible causes of colic. There are many ways to categorize the causes of colic. One is to divide the causes into those that can be resolved by medical treatment alone versus those that require surgical intervention. Most horses with colic respond to medical treatment, and only a very small percentage have a cause that will not get better without surgery. A second useful way to categorize the causes of colic is based on whether the small intestine or large intestine is the source of the pain. This is beneficial because sometimes the veterinarian can differentiate between these two locations during the exam, and treatment and prognosis tend to depend on which part of the intestine is involved. A third way to categorize colic is based on whether it is a one-time occurrence or whether the horse has had multiple episodes of colic over time (i.e. it is a chronic situation). To list the specific causes of colic is beyond the scope of this article. Clinical Signs Colicky horse looking at side, showing signs of rolling The clinical signs (a.k.a. “symptoms”) of colic vary from horse to horse, and can range from very mild to very severe. Some mild signs include a horse not being as interested in feed as normal, having decreased number of manure piles, or quietly laying down more than normal (or at an abnormal time, such as feeding time). A colicky horse may be looking at its side and showing evidence of having rolled (is covered in shavings). Moderate signs may include pawing, lifting the upper lip, looking at the flank, kicking at the belly, or stretching out. Severe signs can include repeated rolling or thrashing and sweating. Every horse is different, so knowing what behavior is normal for your horse is important so you can tell when something is amiss. Also, some horses are extremely stoic whereas others are very are more sensitive and quick to show signs of discomfort, which can make interpretation of signs tricky. It is therefore important to remember that the severity of colic signs you see may not always correlate very well with the severity of the underlying cause. What to Do While Waiting for the Vet If you are concerned that your horse is showing colic signs, you need to call your veterinarian immediately. If you are comfortable doing it, and the horse’s signs aren’t so severe as to prevent it, taking a heart rate and rectal temperature and evaluating the gums prior to calling your veterinarian may be helpful so you have more information for the phone call (ask your vet — (s)he may have a preference as to whether you do this or not). Next time your vet is out, have him or her show you how to take your horse’s heart rate and rectal temperature, and evaluate the gums. Normally a horse’s heart rate should be between 30 and 40 beats per minute. A normal rectal temperature is between 99°F and 101.5°F. The gums provide insight about how well hydrated the horse is and should be pink and moist. When you call your vet, (s)he may ask about the duration of colic signs, if the horse has colicked in the past, how uncomfortable the horse is, and if the horse is passing any manure. There are different opinions on whether to walk a horse while waiting for the vet to arrive. If the horse is rolling and extremely uncomfortable, walking may help keep it quiet. Walking may help alleviate some gas, which can be a cause of colic. A horse should not be forced to walk, and laying quietly is generally okay. Most veterinarians prefer that you do not administer any medications to a colicky horse unless they advise you to do so when you call. This is because a dose of Banamine or dipyrone (or whichever painkillers you have) can make evaluating the horse difficult for the vet. The horse may temporarily look better while the vet is there, only to become colicky again later; thus postponing necessary treatment by the vet and potentially making the situation worse. Situations in which the vet may advise you to administer medication are if it is going to be a long time prior to the vet seeing the horse, or if the horse is dangerously uncomfortable. What to Expect from the Vet Listening to gastrointestinal sounds Once the vet arrives, (s)he will likely examine the horse (take heart rate and respiratory rate, take the rectal temperature, evaluate the gums, and listen to the gastrointestinal sounds). If your horse is extremely uncomfortable, this exam may be brief and the vet will administer intravenous sedation/pain relief quickly. (S)he will then likely ask you a few more questions about duration of colic signs, any previous colic episodes, any recent changes in feed or management, or other medications recently given. The most common initial workup for a colicking horse is for the vet to perform includes abdominal palpation per rectum and passing a nasogastric tube. The horse will likely be sedated for these procedures. Abdominal palpation per rectum (a.k.a. “the rectal exam”) gives the vet information as to whether there is manure passing through, the appearance of that manure, and allows palpation of about the back third of the abdomen. Obviously horses are very large animals, and it is not possible to feel everything in the abdomen. However intestinal distention or impaction and some intestinal displacements can be palpated, so this is very informative. Sometimes this is not done if either the colic is very mild, or if the veterinarian does not feel safe doing the exam. There is obviously a degree of risk in standing directly behind a horse and performing a rectal exam, which is why at veterinary clinics this procedure is preferentially performed in the stocks. Nasogastric tube passed to check for nasogastric reflux Passage of a nasogastric tube has two distinct purposes. First, horses cannot vomit, so if the stomach is very full due to an obstruction of the intestine, it can get very distended. This is not only extremely painful, but it is fatal if the stomach ruptures. The quantity and quality of the reflux is useful information; it can help differentiate between small intestinal and large intestinal causes of colic. A normal horse may have 1 to 2 liters of nasogastric reflux, versus a horse with a small intestinal obstruction can have upwards of 20 liters of reflux. Second, a nasogastric tube is an excellent way to administer fluids and electrolytes to help rehydrate the horse. Horses with colic generally have some degree of dehydration. Additionally, your vet may add either mineral oil or detergent or epsom salts to the fluid to help soften the bowel contents. If your horse becomes colicky again once the sedation and pain medications have worn off, or the initial colic is severe, your vet may recommend intravenous fluids and additional treatment. Depending on the horse’s condition, the vet’s preference, and the available facilities, this may be done at the farm or (s)he may advise taking your horse to a referral veterinary clinic. At the Clinic If your horse is referred to a veterinary clinic (or some vets may have resources to do some of this in the field), diagnostics such as abdominal ultrasound, abdominal radiographs, abdominocentesis (a.k.a., “the belly tap”), or gastroscopy may be performed. These are four different ways to evaluate different parts of the gastrointestinal tract and gather more information. While every attempt is made to determine the cause of colic, the horse’s level of pain is the single most important deciding factor as to whether surgery is necessary. If a horse is repeatedly uncomfortable in spite of adequate pain medication and hydration, the cause of the colic is very likely something that is not going to resolve without surgery. If surgery is indicated, the vet will discuss with you his or her thoughts on the possible causes, tell you about the surgical procedure, and talk about the costs. Possible Preventative Measures Colic can be frustrating because, in a lot of situations, a reason for the colic episode is not determined. Possible causes that often are discussed include weather change (so the horse is not drinking enough water), change in feed, poor dentition, and parasites. While it is probably not possible to prevent all episodes of colic, there are certainly some things owners can do to minimize the risk. Regular feeding schedules are very important for gastrointestinal health. If any feeding changes are to be made, they should be done slowly over a week or two. Horses were also designed to graze and therefore they are suited to more frequent smaller feedings when possible. It is important to make sure there is always access to fresh, clean water. Note how much water your horse drinks, and be cognizant of decreases if there is a weather change and try supplementing water in other ways at those times. For example, feeding a soupy mash or adding a few tablespoons of apple juice or Gatorade to the water to tempt the horse (obviously always have available both plain and flavored water). Horses living on sandy soil should be fed in feeders with rubber mats underneath to minimize the amount of sand they ingest. Additionally, horses in sandy areas should be on a preventive psyllium program to help clear them of sand they take in. Studies have shown that horses in California (in particular, Arabians) that eat alfalfa are more likely to have enteroliths (stones that form in the colon that can cause colic and have to be removed surgically). Therefore, while alfalfa is a great feed source, it may be recommended to not feed it for more than 50% of your horse’s diet. Routine deworming is important for many reasons, and can help decrease the incidence of some types of colic. Routine dental care is critical, not only in older horses, because poor dentition can increase risk of impaction colics. Conclusion Certainly there are numerous causes of colic, but some of these can be avoided with routine good horse care and by being well-informed. Being armed with a little more information about colic can hopefully help to decrease the preventable risks and make a colic event less scary.

Steinbeck Peninsula Equine veterinarians recommend administering spring vaccinations for horses, mules, and donkeys in advance of warming weather. Our veterinarians will custom-tailor a risk-based vaccine recommendation to meet your animal’s specific healthcare needs. Dr. Hailey Everett encouraging her equine patient to relax while performing a draw for annual, routine bloodwork Download t his PDF to print and share. Bundle Spring Vaccinations with Important Routine Healthcare When our mobile veterinarians call on you at your facility or you and your equine companion visit our clinic for spring vaccinations, it is also an excellent opportunity to have blood drawn for routine bloodwork and to provide a manure sample for a fecal egg count (FEC). Ask about our special "bundle pricing." Why is annual bloodwork  important? Routine bloodwork can help detect signs of infection, as well as issues with organ systems. For example, horses on long-term medications such as Banamine, Bute, or Equioxx are at increased risk of kidney and gut issues. Early detection and treatment can be invaluable in these cases. Routine bloodwork also offers a baseline, which we can use as a comparison in case of illness in the future. Why should you get a fecal egg count?   Due to the high incidence of parasite resistance, the strategic use of de-wormers is key. De-worming based on the results of a fecal egg count (FEC) is the current gold standard for effective equine parasite control. Plus, programs that offer colic treatment insurance typically require an annual FEC. Learn how to collect manure for an FEC... The Great Vaccination Debate If you're unsure whether or not to vaccinate or want to learn more about the pros and cons, check out this article  by Steinbeck Peninsula Equine Clinics Internal Medicine Director, Dr. Laramie Winfield.

By Laramie Winfield , DVM, DACVIM, cVA, CVMMP Annual vaccinations are a large part of our preventative health strategy here at Steinbeck Peninsula Equine Clinics. As your veterinarians, we are happy to be one of your main sources of information concerning your horse’s health and vaccines. However, we also realize that many owners would like additional opinions and sources of information. While there are many excellent sources of information available to you on the internet, there are also many sources of information that are misleading, incorrect, and full of misguided advice. The American Association of Equine Practitioners (AAEP) provides a compendium of sound information and Guidelines for Equine Vaccination . Should you vaccinate your horse or not? An article from Horse & Rider titled " Vaccine Wars: The Great Debate " does an excellent job of answering many of the common questions we hear about vaccination and if it is necessary for your horse. We do recognize that some horses are very sensitive to vaccination and alternative vaccine forms and schedules may be best for those horses. Each horse and situation may benefit from a different protocol and we are happy to develop an individual plan for you and your horse. Rabies is a fatal disease that can be transmitted to humans. Given the severity and significance of rabies infection it is included in the core vaccines recommended for horses. The UC Davis School of Veterinary Medicine offers more information in the article " Do Horses Need Annual Rabies Vaccination? " West Nile is a mosquito born viral disease transmitted to horses causing neurologic signs, fever, and in 30% of horses is fatal. Given that available vaccines are highly effective at preventing disease and safe to administer we strongly support the administration of vaccines to protect against West Nile Virus. The California state government monitors new cases an offers a website with updates and more information on West Nile virus .

Steinbeck Peninsula Equine Clinics Veterinary Assistant Annabelle Arthur shows us some of what's typically on our mobile services trucks when our equine veterinarians make ranch calls.

By Kayla Dykstra, DVM, cVA Foaling can happen fast. Being well prepared helps keep your mare, foal, and care-givers safe and stress-free. Preparation = Peace of Mind When you ascertain that your mare has become pregnant, download, print, and implement this Pre-Foaling Checklist . Take Care of Maternity Health Care Pre-foaling vet-check appointment   Vaccinations up to date  Deworming plan followed Prepare Foaling Area Clean, disinfected stall Deep, clean bedding (straw preferred) Good lighting and ventilation No sharp edges or hazards Veterinarian contact info posted Assemble Foaling Kit Supplies Clean towels Gloves Tail wrap Antiseptic solution Thermometer Flashlight Notebook and pen Be Ready for an Emergency Veterinarian contact saved in phone Phone charged Emergency transport plan in place Before Foaling: Monitor Your Mare Perform daily checks as the due date nears, progressing to every few hours overnight: Watch for udder changes and relaxation Note behavioral changes Most mares foal without issues but knowing what’s normal — and when to call the vet — can make all the difference. After Foaling: Follow the “1-2-3” Rule If any  of these three time-markers are not met, contact a veterinarian immediately! Foal should stand within 1   hour. Foal should nurse within 2 hours. Mare should pass placenta within 3 hours. Steinbeck Peninsula Equine offers foaling out services, so if having your mare foal out under the experienced care of our veterinarians makes your life more stress-free, contact us any time.

By Timothy G. Eastman , DVM, DACVS, MPVM, published in Bay Area Equestrian Network July 2006 Veterinarians are frequently called upon to help horse owners control the estrus behavior (“heat”) in mares used as performance horses or as show animals. When some mares come in heat, the hormonal and behavioral shifts that takes place distracts from their ability to perform their sport. Mares have a 21 day heat cycle. They are in “estrus” for about 1 week and then in “diestrus” (out of heat) for approximately 2 weeks. While in estrus, the ovaries produce large quantities of estrogen that is responsible for the changes in behavior. After they ovulate, the ovary produces the overriding hormone progesterone, which is responsible for suppressing the estrus behavior. Before deciding to manipulate your mare’s hormones, you should consult with your veterinarian. Sometimes a mare’s history can be suggestive of a hormonal problem. For example, a mare with a granulosa theca cell tumor of one of her ovaries often displays stallion like behavior. There are several ways to maintain a high level of progesterone in mares thereby suppressing estrus behavior. The most reliable and the most common method is to administer an oral form of progesterone known as Regu-Mate®. This is the only method of progesterone supplementation in mares that has been approved by the Food and Drug Administration. Regu-mate works very well at suppressing estrus behavior, is easy to administer, and does not have any long term adverse effects associated with its use. The down side is it is relatively expensive (about $4.00/day) and can cause menstrual cramps in women if it comes in contact with their skin. If administering this drug you should make sure you have one of the dosing “guns” they sell for safer delivery. There are also intramuscular shots of progesterone available that provide the desired effect in some mares. The down side is the need to administer shots on a regular basis, expense involved, off label drug use, and reduced efficacy. For many years, veterinarians would use cattle progesterone implants placed under the skin of horses to prevent estrus. This involved a minor surgical procedure and off-label use of the product. Research has shown that this method of progesterone supplementation is largely ineffective in horses and has been abandoned by many. One of the newest methods of estrus suppression was suggested at a fairly recent meeting of the American Association of Equine Practitioners and involves placing a Uterine Glass Ball (UGB) in a mare’s uterus at the end of her heat cycle. Uterine glass ball is just a little more medical sounding than marble, which is what it is. We get them at the toy store and they need to be 35mm in diameter (a “shooter”). Nobody has proven why this can be effective but some feel that the marble signals the uterus similar to a pregnancy. Our experience has been that this technique is effective in about 50% of mares which is similar to the published data. The marble should be removed towards the fall when mares typically stop cycling. Another way to suppress estrus behavior that often goes overlooked is spaying. People think of spaying oftentimes as a procedure for just dogs and cats but it can be a very feasible option for owners of performance mares with no plans to ever breed. Spaying mares has had a precarious past as it used to involve a dangerous procedure with a scary complication rate. The widespread use of laparoscopy in horses has revolutionized spaying of mares. There are many laparoscopic techniques available to do this, and all have advantages and disadvantages. Dr. Tom Yarbrough, a boarded surgeon from the Sacramento area has developed an exciting technique that is probably the least traumatic way to spay a mare yet. One of the main issues with spaying a mare by any means is how to control bleeding where the ovary is removed. Laparoscopic sutures can be difficult to place and laparoscopic stapling equipment is very expensive. Dr. Yarbrough found that if you occlude the blood supply of mare’s ovaries, you do not have to remove them. Left in place and with no blood supply, the ovaries appear to turn to fat and not produce anymore hormones. This is accomplished with a “zip-tie,” yes the thousand-and-one use zip ties you have in your kitchen drawer. The zip-tie is introduced into the mare’s abdomen through a laparoscopic instrument. The ovary is manipulated through the loop which is carefully tightened and the free end cut short. The procedure has been effective at reducing or eliminating estrus behavior in about 100 test mares. To get a feel for the behavioral changes you can expect, try a several week course of Regu-Mate first. Once spayed, the mare’s behavior should be close to what it was like while on Regu-Mate. Mares are held a gradually decreasing diet for several days before surgery because it is important to have their intestines as empty as possible prior to surgery to aid in visualization. The procedure generally takes about an hour and leaves two stitches on either side of the abdomen which are removed in several weeks. While other procedures to spay mares oftentimes cause abdominal discomfort for several days, mares undergoing the laparoscopic zip-tie procedure generally are back on full feed that night. Hospitalization is typically for about 4 days and they go back to work in several weeks.

By Alexandra Eastman , DVM, MS, published in Bay Area Equestrian Network November 2007 It’s never too soon to start thinking about next year. Planning ahead can make breeding your mare less stressful and more fruitful. Many broodmare owners can run through breeding programs in their sleep, but for those new at the game, the following may be helpful in demystifying the process of breeding your mare. More than Two Months Before Breeding Discuss with your veterinarian the pros and cons of breeding your mare. There are many things to consider. How is your mare’s general health? Healthy mares that are not over or underweight tend to be most fertile. How old is your mare? Does she have any congenital problems that you would not want to pass on? Because of love they feel for their mare, many people overlook the consequences of breeding mares with undesirable heritable traits. Is she reproductively sound? A breeding soundness exam can help evaluate the reproductive health of your mare. If done early, it can help by identifying problems that may need treatment before you are trying to breed. During this time you may also want to research prospective stallions. You will want to establish a breeding contract ahead of time with the stallion owner. This is a time for you to familiarize yourself with the details of the contract. You may want to ask about the pregnancy rates of the stallion, the fees you will incur during the process, the collection days, and breeding season. Which stallion you choose may effect how your mare will be bred. Mares are bred by natural cover or by artificial insemination (AI). If your mare is to be bred by natural cover, you will probably transport your mare to the stallion for breeding. If she is to be bred by AI and the stallion ships well, it is possible for her to be bred with transported semen. Transported semen comes in one of two forms: cooled or frozen. There are advantages and disadvantages to each method. Pregnancy rates are highest in mares bred by live cover or artificially inseminated immediately after collection. However, transporting the mare to the stallion may not be practical or desirable. In most cases cooled semen has higher pregnancy rates than frozen semen but cooled semen must be ordered and shipped for each breeding. Depending on the collection schedule and shipping methods offered by the stallion owner, this can be difficult to orchestrate with the actual ovulation of the mare. Frozen semen is nice because it sits in the tank waiting for the mare but the conception rates are lower and the timing must be more precise so the mares need to be checked more frequently by a veterinarian. Breed registries have differing rules regarding AI and transported semen. If you intend to register your foal, you should check the rules of your specific breed association. Two Months Before Breeding Mares are seasonal breeders. They cycle, produce and release ova from follicles, during the months with the longest day length. During the winter they enter a period of diestrus and stop cycling. As mares begin to cycle in the early spring, they enter a period of transition. During this time the mares may show signs of being in heat but their cycles tend to be unpredictable making it difficult to achieve good pregnancy rates during this time. Without any intervention the ideal time to breed mares in the northern hemisphere is May through August. During this stretch of time, the mares are usually cycling consistently and are most fertile. The length of gestation is extremely variable but pregnancy usually lasts about 340 days. For many breeds the foals have an automatic birthday of January 1 st. Foals destined for age group competitions will have an advantage if they have an actual birth date early in the year. For owners hoping for birthdays early in the calendar year, May through August is usually considered too late to be acceptable breeding dates. The simplest and most effective method to get a mare to cycle earlier in the year, is to increase her “day length” 60 days before you want her to start cycling. For most mares this means adding light to their stall starting on December 1st. The most common method is to add light at the end of the day before dusk making the mare’s day length 15-16 hours/ day. This can be most easily achieved by placing the lights on timers to light the stall from around 4:30 pm to 10-11pm each day. Leaving the lights on all night or skipping days will negate the effect. The lights do not have to be overly bright. The rule of thumb is that you should be able to comfortably read a newspaper. One Month Before Breeding If possible, start teasing your mare to determine her heat cycle. Mares that are in estrus (heat) usually stand calmly, squat and wink the labia of the vulva in the presence of a stallion. They often raise their tail and urinate. Mares that are not in estrus tend to be more agitated in the presence of a stallion. They are restless and may lay their ears back, squeal and kick. Some mares will tease to geldings or other mares when they are in heat. Other mares will not overtly show signs of estrus even when teased with a stallion. Many mares with foals are so protective of the foals that they won’t show estrus behavior. Teasing is not always possible. Your veterinarian can determine the stage of estrus by examination of the ovaries, uterus and cervix of the mare. If your mare is to be bred with transported semen, contact your veterinarian to determine when they would like to start following your mare’s cycle. If your mare is going to travel to the stallion farm, contact the breeding manager or stallion owner to determine when they would like you to bring your mare. If your mare is to travel out of state, be sure to check with your veterinarian about the timing and requirements for an interstate health certificate and Coggins testing for the state in question. Desired Breeding Time Arrange for breeding either by your veterinarian or the stallion manager. The attending veterinarian will probably want to check your mare after breeding to ensure that she has ovulated and that she did not acquire any post breeding fluid within her uterus. Even with the use of drugs to induce ovulation, some mares do not ovulate when expected. If this is noted on a post-breeding exam, there may be a chance to order more semen. Many mares, especially older mares, will have difficulty clearing fluid from their uterus after breeding. If this happens, it can provide an inhospitable environment for the embryo and the pregnancy will be lost prior to implantation. Oxytocin with or without uterine lavage can greatly increase the chances of a viable pregnancy Pregnancy Exams Pregnancy can usually be diagnosed by ultrasound 14 days after ovulation. A fetal heartbeat can usually be detected ultrasonographically at day 24 or beyond. At the heartbeat check be sure to discuss with your veterinarian protocols for vaccination (most veterinarians recommend EHV-4 vaccination at 5, 7, and 9 months of gestation as well as core vaccinations 1 month prior to foaling). Specific recommendations may vary between veterinarians or by region. It is very nice when everything goes as planned. You find a stallion, your mare comes into heat, she is bred in a timely fashion and she takes the first time. This does happen sometimes. However, like it or not, mares are individuals and they don’t always come into heat when you expect them to, ovulate when they should, or they have trouble with post breeding fluid. Sometimes the semen misses the connecting flight or the stallion is collected Monday, Wednesday and Friday and they only ship FedEx and you really need the semen on Monday and you are out of luck. Generally the most effective tool in a successful breeding season is good communication. If you have all of your questions answered ahead of time by your veterinarian and by the stallion manager and you are kept up to date as the process unfolds you shouldn’t have too many surprises.

Learn about the prevalence of equine gastric ulcers, what clinical signs suggest horses may have them, how they are diagnosed, and how they can be prevented and treated, in this Equine Gastric Ulcers presentation by Steinbeck Peninsula Equine veterinarian Jen Williams .

Learn about equine NSAIDs (non-steroidal anti inflammatory drugs), their appropriate use and ongoing management, risks, and potential adverse effects for horses, ponies, mules, and donkeys, in this Responsible Equine NSAID Use presentation by Steinbeck Peninsula Equine veterinarian Dr. Andrea Frei .

This Equine Winter Wellness presentation by Steinbeck Peninsula Equine veterinarian Dr. Zöe Davidson will help you make sure your horse, pony, mule, or donkey is well prepared for chilly winter weather.

Pituitary pars intermedia dysfunction (PPID) — also known as equine Cushing's disease — is an age-related, slowly progressive, degenerative disease that affects many horses. Typical signs that your horse may have PPID include a long, wavy hair coat that doesn’t shed, excessive thirst and urination, muscle wasting, and increased susceptibility to infections and laminitis. If you suspect that your horse may have pre-Cushing’s or Cushing’s disease, it’s important to discuss this with your veterinarian and begin a treatment plan that may include medication as well as dietary management and general wellness care to promote longevity and ensure a good quality of life. The Equine Endocrinology Group (EEG) is composed of experts who provide advice in the form of written guidelines to help veterinary practitioners diagnose and manage equine endocrine disorders. Guidelines are updated every two years. Here are the most recent guidelines, released in October 2025: Learn more: https://www.bicanadaequine.ca/ppid/ppid-symptoms

By Nora Grenager, VMD Updated in 2020 (originally published in Bay Area Equestrian Network September 2006) Example of severe chronic laminitis The two main endocrinologic concerns in horses are equine Cushing’s disease (also known as pituitary pars intermedia dysfunction) and equine metabolic syndrome (also known as “insulin dysregulation” or, formerly, “insulin resistance”). These disorders are increasing in prevalence as our equine population is better cared for and living longer, and improved diagnostics are available. There are two main similarities between these conditions: 1) insulin dysregulation, and 2) the potentially devastating possibility of laminitis. While it is an area of much research, there are numerous theories as to why these horses are predisposed to laminitis, and it is beyond the scope of this article to discuss them all. However, laminitis is likely related to insulin dysregulation, which is a reduced ability of the body to respond appropriately to insulin released by the pancreas after eating a meal. It is important to understand the signs of insulin dysregulation and be able to effectively manage these horses to decrease the risk of laminitis. Equine Cushing’s Disease Very hirsute horse The cause of equine Cushing’s disease is a benign tumor, likely caused by oxidative stress, in a part of the horse’s brain called the pituitary gland. It is not a typical neoplastic tumor, rather a lack of regulation of hormone secretion due to alterations in local factors in that region of the brain. This alteration (namely, a decrease in local dopamine production) leads to unregulated hormone secretion by the pituitary gland, enlarging this area such that it forms a tumor. This tumor secretes a variety of hormones, including one called adrenocorticotropic hormone (ACTH) that causes the adrenal gland (in the abdomen) to release increased amounts of steroid (cortisol). Other secreted hormones include α-MSH, POMC, and β-endorphin. The increased levels of these circulating hormones cause the typical clinical signs , including: a long, wavy hair coat that does not completely shed out; abnormal fat distribution, such as a cresty neck or fat pads above the tailhead; weight loss, especially over the ribs; muscle loss, along the top line or leading to a pot belly; recurrent laminitis; lethargy and exercise intolerance; increased sweating, increased water intake and urination; and immune system suppression or recurrent infections. Many horses with Cushing’s disease also have chronic insulin dysregulation. The most common clinical signs are the abnormal, long hair coat (called “hirsutism”) and chronic laminitis. However, it is important to remember that horses with milder disease can have milder signs, and a long haircoat may not be seen in all horses with Cushing’s. Equine Cushing’s disease is more common in older horses (in their late teens to 20s), but can be seen in horses as young as 7 years old. There are some breeds that seem to be more predisposed, and ponies also seem to be predisposed to the condition. Example of a cresty neck Definitive diagnosis of equine Cushing’s disease can be challenging. It is relatively easy to diagnose in an older horse with more severe disease and typical clinical signs, such as a long hair coat and laminitis. In these cases, in which the horse has the typical clinical signs of equine Cushing’s disease, diagnostic tests are sometimes skipped because the signs are so suggestive. Remember, though, that having lab values to monitor is very helpful so testing should be done when possible. Yet sometimes a “diagnostic therapeutic” challenge is used, in which we try treating a horse for 30-60 days and monitor the response; the treatment for Cushing’s (pergolide) is so effective and safe that we have our answer if the horse improves on medication. There are several tests available. The difficulty with all the available tests is that they can be negative in horses with early Cushing’s disease; thus, if the index of suspicion is very high, we may still opt to treat the horse even if the test is negative. The first recommended test is measurement of the resting levels of ACTH, one of the hormones that is overproduced by the tumor in the pituitary. This test requires one blood sample. While it is fairly accurate, it still can have false negatives (i.e., about 30% of the time horse with Cushing’s disease has a negative test result). If the resting ACTH levels are normal, the next recommended test is called the thyrotropin releasing hormone stimulation test (the TRH stim test). This test is slightly more sensitive (i.e., more likely to correctly diagnose the horse with Cushing’s), but requires two blood samples, taken 10 minutes apart, and intravenous administration of TRH. The test is very safe but is obviously a bit more expensive than just measuring the resting ACTH once. The dexamethasone suppression test is another test that is slowly falling out of favor as the ACTH testing has been shown to be more reliable. This test requires two veterinary visits: at the first visit, blood is drawn to measure the cortisol level and a dose of dexamethasone is given. At the second visit, about a day later, blood is drawn to again measure the cortisol level. The test relies on a normal endocrine negative feedback loop. In a normal horse, a dose of dexamethasone (steroid) suppresses the pituitary gland, telling the gland that it is unnecessary to make more cortisol (steroid made by the body) because some has just been given. Therefore the second sampled blood level of cortisol is very low in a normal horse. In a horse with Cushing’s, the tumor in the pituitary gland results in production of cortisol no matter what levels of steroid are in the body, so it does not respond to the dexamethasone the veterinarian administers; therefore the second level of cortisol is not significantly different from the first, pre-dexamethasone, level. This test can also have false positive or false negative results. There are two potential drawbacks: first, it necessitates two visits from your veterinarian, which increases cost. Second, it involves the administration of steroid to a horse that is already possibly predisposed to laminitis. Therefore there is a very low risk of precipitating a bout of laminitis. Most practitioners feel, however, that the benefits of knowing the test results often outweigh the risks. It has recently been shown that the tests for equine Cushing’s disease are even more sensitive in the late summer/early fall (i.e., mid-August through mid-October); therefore, veterinarians may recommend testing at that time. A variety of other tests exist, and there is ongoing research to develop even more sensitive and specific ways to diagnose equine Cushing’s disease in those horses in which the diagnosis is difficult. The astute reader may be asking why we do not just measure cortisol levels, since the overproduction of that hormone is a hallmark of the disease. Unfortunately, the daily variations in cortisol levels render this measurement useless. Evaluation for insulin dysregulation should always be performed with with tests for Cushing’s disease since many horses with Cushing’s have concurrent insulin dysregulation. Discussion on the diagnosis of insulin dysregulation is in the following section. Treatment is advocated because of the possibly devastating effects of laminitis and immune suppression. Fortunately, there is a highly effective specific treatment for equine Cushing’s disease called “pergolide.” Pergolide acts like dopamine and works on the pituitary gland to prevent the release of excess hormones from the tumor. It is given as a tablet once daily for the rest of the horse’s life. Most of the time a beneficial response is seen in 4–6 weeks, but sometimes the dose needs to be increased or decreased. Pergolide has virtually no known side effects in horses at appropriate dosing levels; some horses will become mildly inappetant when the medication is first started. The appetite returns in these horses when they are started on a lower dose and it is gradually increased. Often bloodwork is repeated to help monitor response to treatment, and generally the response to treatment is easily seen. The trade name for pergolide is “Prascend®”—while there are compounded versions of pergolide that are less expensive, they are considerably less reliable and effective, so in the long run end up costing more for less effect. Several other drugs (such as cyproheptadine and trilostane) have been used to treat equine Cushing’s disease, but none have been shown to have the efficacy of pergolide. Occasionally one of those drugs is added to pergolide treatment in severe cases that need additional therapeutic help. Many nutritional or herbal supplements are also available (often including magnesium and chromium or chasteberry), and may have variable efficacy; however, none have been proven to be safe and effective. Often these horses also have insulin dysfunction, so treatment for that will be similar to what is described in the next section. The proper treatment of Cushing’s disease with pergolide eventually alleviates many of the signs of insulin dysregulation since the underlying cause is being treated. In addition to daily medication, some feed and management changes should be considered. These horses need regular farrier care, good dental care (immune suppression and older age make them prone to dental problems and secondary sinus infections), routine preventive veterinary care including fecal egg counts, and good quality feed. Some horses may need to be clipped to help prevent hyperthermia. High starch/sugar feeds should be avoided in the horses that have insulin dysregulation to help minimize fluctuations in glucose levels. More about nutrition for horses with insulin dysregulation is written in the following section on metabolic syndrome. Horses with Cushing’s that do not have documented insulin dysregulation but suffer from weight loss will have different dietary needs. Equine Metabolic Syndrome Equine Metabolic Syndrome is defined as chronic insulin dysregulation, obesity or abnormal fat distribution (e.g., a cresty neck; fat pads over the tailhead, eyes, and withers), and increased risk of laminitis in horses that do not have equine Cushing’s disease. This is a relatively newly recognized condition, and there is a lot of ongoing research about this disorder and our understanding of it continues to grow. Horses with this condition tend to be younger than horses with Cushing’s disease. These horses have documented insulin dysregulation and sometimes have increased circulating fat levels. Example of horse with metabolic syndrome. Note the cresty neck and excess fat by the tailhead. The cause of metabolic syndrome is not fully understood, but several theories are being closely considered. First, obesity leads to insulin dysregulation (much like people with Type II diabetes). Second, insulin dysregulation develops secondary to abnormal nutritional usage in genetically predisposed animals. Third, fat cells can be metabolically and hormonally active and alter insulin usage in a peripheral Cushinoid-type syndrome. It is logical to think that horses with metabolic syndrome will perhaps transition into equine Cushing’s disease as they age; however, this has not been proven. There are several ways to test for insulin dysregulation associated with metabolic syndrome (and for horses with Cushing’s disease). The most basic, first-line, test is to measure resting fasting glucose and insulin concentrations first thing in the morning before breakfast. Basically, a normal horse should have low insulin levels when glucose levels are normal. A horse with insulin dysregulation has increased levels of insulin (to try to make up for tissue resistance to it). The second, slightly more sensitive, test for insulin dysregulation involves administering a specific amount of light Karo syrup, then testing the blood a specific amount of time later (approximately 1 hour) to monitor the response. A third, more involved, test is the combined glucose-insulin test (CGIT), which is used when insulin dysregulation is suspected but the first two test results are normal. The CGIT involves placing an intravenous catheter, administering glucose and insulin, and measuring the body’s response to this at multiple time points. There is no one specific treatment available for equine metabolic syndrome regardless of whether it is definitively diagnosed or not. Treatment focuses on the management of the insulin dysregulation, including reducing the horse’s weight, dietary management, and increasing exercise. The most important goal of dietary management is to restrict the amount of soluble carbohydrates (often called “nonstructural carbohydrates”) in the feed, because they alter the insulin levels the most. Grazing should be discussed with your veterinarian and many owners use grazing muzzles or dry lots; however, it is not recommended to lock the horse in a stall. Hay can be analyzed (your vet can direct you to a company that will do this) for its soluble carbohydrate content; it is worth doing this if you purchase large amounts of hay at a time. Some types of grass hay have fairly low soluble carbohydrates, and should be fed at 1.5 to 2% of body weight, as directed by your veterinarian. Oat hay should be avoided. If the horse’s hay intake is tapered down to 1% of its body weight and it is still having difficulty losing weight, soaking the hay is a way to further decrease the soluble carbohydrates. It should be soaked in warm water for 20 minutes, or cold water for 60 minutes, immediately prior to feeding. A vitamin/mineral supplement should be fed, and if additional calories are needed they should be provided by sources high in fat and protein, rather than carbohydrates, such as corn oil or rice bran. Sweet feeds, apples, carrots, and high sugar treats should be minimized or, more often, completely removed from the diet. Most feed companies also make low-carbohydrate feeds specifically designed for horses with insulin dysregulation. Unless a horse is currently dealing with a bout of laminitis, increasing exercise is essential to reducing body fat. Some studies have shown that increased exercise also might help improve tissue insulin sensitivity. If a horse is on a good exercise program with a proper diet and still not losing weight, or is in a current bout of laminitis, thyroid hormone supplementation may be recommended by your veterinarian to improve insulin sensitivity. Many horses with insulin dysregulation used to be incorrectly categorized as “hypothyroid.” Further research has shown that very few horses are actually hypothyroid, however many horses with insulin resistance can have low measurable levels of thyroid hormone. However, their thyroid glands are working fine, and the insulin resistance is the main issue. In spite of this, supplementing with thyroid hormone can help boost the metabolism, improve insulin sensitivity, and get a horse to start losing weight. The thyroid hormone is typically given once daily for a couple of months and then tapered down and discontinued. A drug used to treat insulin resistance in humans, called “metformin,” is also used in horses with severe insulin dysregulation. It is typically given 30 minutes prior to feeding and can only be used for a few weeks at a time. Many other medications taken from the human medical field have also been evaluated and tried though many are cost prohibitive in the majority of cases at this time. Also, just as with equine Cushing’s disease, there are many herbal supplements advocated to treat equine metabolic syndrome. Again, there is little proof of efficacy or safety of these treatments, though anecdotally there are some that are beneficial. If you are concerned that your horse has signs of either metabolic syndrome or equine Cushing’s disease, set up an appointment with your veterinarian for an examination and discussion. It is not always easy to distinguish between these two conditions, and they can often be concurrent. Early recognition is critical to provide your horse with the best care and prevent the potentially devastating disease of laminitis. Ideally, endocrine testing would be part of the annual physical exam in all horses.