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August 2019 - Equine Nutrition

With so many supplements and grain options, how should you know what to feed? Join us this month as our expert, Dr. Alison Cornwall answers your questions concerning equine nutrition.



Click here to read this month's questions and answers.

Upper Airway Concerns


  1. I am concerned that my 12-year-old horse may have a sinus infection. I have been administering him penicillin for the last five days. At first, he had drainage from one side of the nose that ran clear and then both sides began running like water. He would not eat or drink. Then it became green discharge from both sides, which eventually cleared, but now it is white and yellow. He is eating a little hay and feed, but he seems to have a problem chewing. I don’t know if it’s sinus or tooth related and unfortunately, I cannot afford a veterinarian bill. (View Answer)

    Thank you for your question! Sounds like your horse is having a little bit of a rough start to the new year.

    Dental issues in horses can certainly cause some of the symptoms that you describe. Fractured or infected teeth can cause poor appetite, difficulty chewing, and/or sinusitis (infected sinus) that would result in nasal discharge. They could also cause excessive salivation or bloody discharge from the mouth. However, the nasal discharge in these cases is more commonly only from one side, unless there are multiple teeth on both sides of the mouth that are affected. The best way to begin investigating for dental issues would be a thorough oral examination by your veterinarian using an oral speculum, which would allow the veterinarian to see the entirety of the mouth. If any broken or infected teeth were identified, they would need to be removed.

    Sinusitis, or a sinus infection, can occur secondarily to dental issues as discussed above, or be primary as a result of an upper respiratory infection. Again, the nasal discharge in these cases is typically only from one side of the nose, and swelling or deformity of the horse’s face on the affected side may be seen as well. Endoscopic examination of the respiratory tract and percussion of the sinuses (tapping them to listen to the sound produced over each sinus – they should be filled with air!) are some of the primary ways that a veterinarian could begin to determine if your horse has a sinusitis. If this were the case, culture of the sinuses to determine an appropriate antibiotic therapy and flushing of the sinus would be the treatment.

    A bacterial upper respiratory infection, particularly one involving the guttural pouches, can also cause the symptoms that you describe, and is more likely to cause discharge from both nostrils rather than just one. It could also cause depression, poor appetite, and/or fever, depending on the case.  Endoscopy of the upper airway, including the guttural pouches, would be the best way to diagnose this. If this is the case, culture to determine the infecting bacterium and the best antibiotic choice would be the next step. However, if there is infection in the guttural pouches, it often needs to be addressed directly with flushing and/or instilling penicillin gel directly into the pouches. Some causes of guttural pouch infection, such as streptococcus equi equi (commonly known as strangles), can be very contagious between horses, so it is important to try to avoid contact between your horse and other horses (both directly and indirectly, such as on your hands, clothes, or buckets) until a diagnosis is made.

    Although I understand that you were trying to help your horse feel better, it is generally a good rule of thumb to not administer antibiotics to your horse without consulting with your veterinarian first. It is important to make sure that the condition you are treating is one that actually requires antibiotics (generally speaking, a bacterial infection), and if so, that an appropriate antibiotic is used for a full course of treatment so that the condition resolves completely. Using antibiotics unnecessarily or for incomplete courses of treatment can not only mean your horse doesn’t get better, but can contribute to the problem of antibiotic resistance, leading to more difficult to treat infections down the road.

    You mentioned being unable to afford a veterinary bill at the moment. As a horse owner myself, I can certainly sympathize with that! Unfortunately, there are several things that could cause the symptoms you describe, and some degree of diagnostics (beginning with a thorough physical exam) will be required to determine what the cause is, and therefore what course of treatment is best. Sometimes, attempting a variety of treatments without first doing the diagnostics to determine the root cause of the problem can end up costing you more money at the end of the day if the treatments do not work. If you are unable to pay with cash or check, many veterinarians accept credit cards these days. If a standard credit card is not an option, CareCredit and Scratchpay both allow you to apply for payment plans specifically for veterinary expenses and may be better for your situation. Another option would be to ask a friend or family member for a loan.

    Best of luck with your horse and I hope that you and your veterinarian are able to get him feeling better soon! Elizabeth Weber, DVM, Ocala, FL

  2. How can a thoroughbred race horse “scope” perfectly and still have breathing problems? (View Answer)

    There are two possible reasons why a horse may have a “clean” or “perfect” scope reported, and yet be found to have breathing issues. The first is that a scope, much like a pre-purchase exam, is only one snapshot in time. While certain types of breathing issues may be congenital (present from birth), others may develop over time, due to factors such as illness, injury, or inflammation. So, the results can change on a horse from one scope to the next. For example, a horse with a traumatic injury to the recurrent laryngeal nerve could show paralysis of one arytenoid cartilage, even if his arytenoid function was entirely normal the week prior. Likewise, a horse with an upper respiratory infection may intermittently displace his soft palate due to inflammation, even if he showed no evidence of displacement on previous scopes. Medications, especially sedatives and tranquilizers, can influence how a horse scopes as well. So, a perfect scope today does not guarantee the same result tomorrow!

    The second reason is due to the difference in circumstances between when the horse is scoped and when the horse is performing. Most endoscopies are performed at rest – when the horse is standing in the stall. Most of the time this is a good approximation of the horse’s airway function during work, especially if the scope is performed fairly soon after the horse is exercised, but there are cases in which the horse’s resting scope does not reflect how he breathes during work. As the horse breathes faster, airway dynamics cause an increase in negative airway pressures, which can affect function. Issues such as pharyngeal wall collapse are generally only seen under these conditions, and so are not observable on a resting scope. Additionally, studies have shown that airway dynamics can be influenced by head carriage, meaning that the way a horse is ridden can influence his airway function during work. So, a horse that shows no abnormalities with his head and neck relaxed in the stall could paint a very different picture when ridden in a tightly controlled frame.

    For horses that fall into the second category, with a normal resting endoscopy but signs of breathing issues during work (primarily, abnormal respiratory noise or poor performance), a dynamic scope may clarify the situation. During a dynamic scope, an endoscope is secured to the horse as it trains and video imaging is relayed to a screen, so that the veterinarian can evaluate the airway function under the conditions of training. This can be done with the horse on a treadmill in a clinic setting, or with the rider on board in the horse’s regular training environment, and may reveal issues that are not appreciable at rest.

    I hope that helps explain why you might find the apparent contradiction of a horse that was reported to have a normal scope, and yet seems to have breathing issues. I suspect you’re not the only person to wonder how this could occur! Elizabeth Weber, DVM, Ocala, FL

  3. What, in your opinion, is the leading cause of poor performance due to respiratory disease? (View Answer)

    Unfortunately, this is a question with no straightforward answer! While some respiratory problems are inherently more severe than others, effect on performance will depend on the type of performance in question, the population of horses looked at, and the degree of severity of the abnormality. In addition, some individuals tolerate certain respiratory issues better than others, in the same way that some can be more or less stoic about musculoskeletal issues.

    In many horse populations, recurrent airway obstruction (RAO, also often referred to as COPD or heaves), is a common performance-limiting respiratory issue, affecting approximately 12% of mature horses to varying degrees. RAO is an allergic respiratory disease in which common environmental allergens cause an inflammatory response in the lungs, resulting in coughing, nasal discharge, respiratory difficulty, and exercise intolerance. Treatment involves environmental management to reduce exposure to these allergens and medical therapy to treat the symptoms, but there is no cure for it. Due to both its widespread occurrence and the degree of effect on performance (due to coughing during exercise and exercise intolerance), in my opinion RAO is a leading cause of poor performance in show and pleasure horses. However, the average age of onset is 9 years, so while it is an important cause of poor performance in mature horses, it is of less concern in the younger horse population.

    In other populations of performance horses, laryngeal hemiplegia is a significant cause of poor performance, especially when it has progressed to complete paralysis. In a normal horse, the two arytenoid cartilages in the larynx are pulled upward and outward as the horse breathes in, opening the airway to allow air to flow through normally. With laryngeal hemiplegia, the nerve controlling one of these cartilages (nearly always the left side) does not function normally, and so the cartilage does not move as it should. The degree of severity can range from a mildly delayed opening to complete paralysis of the cartilage. When complete paralysis of one cartilage occurs, air has significantly less room to pass through the larynx, causing an increase in airway resistance and an increase in respiratory effort. In horses doing strenuous work, such as racehorses or high-level sport horses, this results in an abnormal respiratory noise and exercise intolerance, leading to poor performance in many cases. This condition can be addressed with surgery (prosthetic laryngoplasty, often referred to as a “tie-back”) and performance typically improves post-operatively, but these horses still do not generally reach their full performance potential.

    There are certainly other causes of poor performance related to the respiratory tract (exercise-induced pulmonary hemorrhage, dorsal displacement of the soft palate, epiglottic entrapment, and shipping fever, just to name a few), and severity of all issues can be variable. However, in my opinion, the above are two of the most significant due to the combination of their prevalence and their impact on normal respiration, leading to decreased performance. Elizabeth Weber, DVM, Ocala, FL