At McGee Equine, we have a special love and respect for senior horses. We have had numerous retirees over the years, and currently have a 29 year old mare of our own. We strongly feel that age is not a disease, and our veterinarians take great pride in working together with owners to help extend both the quantity and quality of life for our seniors. Let’s face it: Your older horse wouldn’t have stayed at your place this long if you didn’t love them. These horses may be the “bomb-proof” kids’ horse, or the one that really takes care of you on a trail ride, or your first pony from childhood. Whatever the story, our senior friends need special care, that we enjoy providing.
One of our biggest practice philosophies is that “An once of prevention is worth a pound of cure”. This is especially true with our senior horses, and we believe that all senior horses should have a wellness physical exam once per year. This is an opportunity for us to examine your horse from head to tail, and pick up on subtle changes that may indicate an underlying issue. Our wellness examinations are a thorough physical examination including listening to the heart, lungs, and GI tract, taking a body condition score, checking lymph nodes, taking the temperature, examining the skin, teeth and eyes, palpating the limbs and flexing joints, feeling the digital pulses and examining the hooves.
You might be asking, “Why does my horse need an exam like this? He seems perfectly healthy.” For the same reasons that your physician recommends a yearly examination for you, your horse (and sheep, goat, and camelid too!) should be examined at least once yearly by a vet, even if nothing seems to be the matter. In our opinion, it’s even more important for your animals to receive this routine exam than it is for you! Our domestic animals don’t live as long as humans, which means they age faster than we do. More things change from year to year, making an annual exam even more crucial. Not to mention, our animals can’t tell us in words what might be troubling them – finding an abnormality on a physical exam might be the first sign of disease. We can start treatment earlier in a disease process, before it becomes chronic in nature or more advanced and severe.
One of the biggest challenges facing our senior horses is maintaining a healthy weight. Often, these guys can drop weight seemingly overnight, whereas it feels like it can take months to put the weight back on. A huge component of maintaining a healthy weight involves dental healthcare. We are firm believers that all medical conditions are easier to treat when caught early, and this is especially so for our older horses. We suggest that every 6 months we perform a thorough dental examination of your horse with a mouth speculum, lights, mirrors and dental probes.
Because horse teeth are continually erupting, if the horse lives long enough, he will eventually run out of tooth root. We liken this to running out of lead in your mechanical pencil. When the horse runs out of roots, he will often start loosing teeth. These teeth may fall out on their own (you can sometimes find them in his grain bucket), or more problematically they can become displaced in the mouth, often with the sharp roots poking the horse in the gums, cheeks, or roof of the mouth. This can cause pain on chewing, and can lead to trouble eating, drooling, weight loss, or infections and odor from the mouth or nose.
Another dental diseases that we commonly see in our seniors is diastema formation. As the tooth runs out of root, the root of the tooth narrows relative to the crown. Because of this, gaps (Diastemas) can develop between the teeth that are narrower at the crown than the root. This essentially creates a one way valve for feed to get in, but not out. This allows feed to pack between the teeth, which can cause pain, but is also a source of infection. Diastemas can be managed by out veterinarians by widening the channel between teeth, to allow feed to move out of the gap again.
EOTRH is another dental disease that can be seen in seniors; no one knows why EOTRH occurs, but it is a very painful condition. EOTHR is short for Equine Odontoclastic Tooth Resorption and Hypercementosis, which is a very painful dental disease that occurs in older horses when their body resorbs the bone and tissue surrounding the incisor (and sometimes canine) roots. Sometime cementum—the enamel-like material that covers the horse’s tooth—proliferates near the gumline, which is believed to be the body’s way of trying to stabilize the tooth as the normal structures deteriorate. Feed can accumulate, followed by infection in the gingival pockets, and the teeth can even fracture.
Signs of EOTRH may include horses being unable or unwilling to grasp hard treats, such as apples or carrots, using their lips instead of their teeth to grasp hay and grass, or spending an abnormal amount of time mouthing at their water bucket. Some horses exhibit a “smiling” behavior, pulling the lips back at both rest and work, whereas other show nonspecific signs of dental pain, such as headshaking, resistance to the bit, hypersalivation, poor appetite, and weight loss.
This condition mainly occurs in horses older than 15, and warmbloods and Thoroughbreds are more commonly affected than other breeds. Horses with a history of dental care performed by a lay dentist or those that have undergone aggressive procedures such as incisor reduction were more than five times more likely to develop EOTRH. Horses with limited pasture access or consuming feedstuffs that did not require a lot of chewing, such as those on alfalfa-based diets, were also at risk. Finally, horses with certain medical conditions, such as Cushing’s, are more likely to develop EOTRH than healthy horses.
Our veterinarians can confirm an EOTRH diagnosis based on both a physical examination of the teeth and intra-oral radiographs (X rays), which are essential to revealing the extent of the destructive process hidden beneath the gumlines. Based on the X-ray images, and the clinical picture of your horse, we may recommend antibiotic treatment to help prevent excessive bacteria accumulation and local infection contributing to the resorption and damage. However, in most cases we recommend that extracting the affected teeth. Removing the teeth relieves the pain associated with each tooth and might even prevent the process from expanding to nearby incisors. While incisor extraction might seem like a radical procedure, these horses do very well afterward. They feel so much better when these painful teeth are removed! These horses learn to use their lips and their tongue to prehend grass and hay, and because incisors were never intended to grind food in the first place, these horses are still able to eat hard feeds.
Equine Cushing’s disease is a fairly common in the horse industry; that’s because 1 out of 5 horses over the age of 15 have the disorder! The term Equine Cushing’s Disease was coined for the similarity to the syndrome in humans and dogs; Cushing’s disease in humans was originally described by a neurosurgeon at Johns Hopkins University named Harvey Cushing. In humans and dogs, Cushing’s is most commonly caused by either 1) an adrenal tumor or 2) a tumor in the anterior lobe of the pituitary gland which causes excessive growth of the adrenal gland. Both of these cause an increase in cortisol (a steroid). In horses, Cushing’s is primarily due to a tumor in the intermediate lobe of the pituitary gland, but there is no associated growth of the adrenal gland. That’s why the technical name of it is Pituitary Pars Intermedia Dysfunction (PPID). Similar to Cushing’s disease in humans but affecting a different area of the pituitary gland, PPID is associated with elevated levels of hormones in the blood. Horses with the condition often have a wide range of clinical signs depending on the stage of the disease, from loss of energy to muscle wasting, and the condition is more common in older horses.
As the pituitary tumor grows, it secretes a hormone called ACTH (Adreno-CorticoTrophic Hormone) This hormone signals the adrenal gland to secrete cortisol, also known as a “stress hormone”. The chronically increased level of steroids in the body wreaks havoc on the balance that the system usually tries to attain. This is what leads to the common signs of PPID, including loss of energy, excessive hair growth, slow or incomplete shedding, or abnormal patches of hair, lethargy, weight loss/muscle wasting, recurrent infections (such as hoof abscesses and sinus infections), chronic laminitis, pot-bellied appearance, or development of fat pads over the eyes. If we see horses with these signs, we will recommend further testing.
In order to definitively diagnose Cushing’s we will perform a test called Thyrotropin Releasing Hormone Stimulation test (TRH Stimulation for short), which is the test currently recommended by the Equine Endocrinology Group, a group of veterinarians specializing in PPID. TRH causes the pituitary gland to release more hormones and ACTH concentrations increase to a higher level in horses with PPID, compared to horses without PPID. This gives us a very reliable test to determine the presence or absence of Cushing’s disease and has been shown to be more reliable than a baseline ACTH. This test is easily performed on the farm by injecting TRH intravenously, and collecting a blood sample 10 minutes later. The blood sample is then centrifuged on the farm, and sent to the laboratory for testing.
Treatment for Cushing’s disease includes a combination of medical therapy as well as management. Currently, the only approved drug for Cushing’s Disease is Prascend® (pergolide). This is a daily medication that will need to be given for the remainder of the horse’s life. This drug aims to reduce the amount of circulating ACTH, thereby decreasing cortisol levels. We often see a quick turnaround with horses once we start them on Prascend – owners will often comment that their horse seems to have “dropped 10 years” a month or so after treatment starts. Once a horse is started on Prascend, we will perform recheck a TRH stimulation test in 30 days to ensure that he is on the correct dose of medication. The other aspect of treating Cushing’s is management. Appropriate foot care is important, to reduce the incidence of hoof abscesses and laminitis, and horses with Cushing’s disease should always be managed more carefully with regards to wounds and parasite control, since their immune system is often not 100% normal due to the effects of cortisol, so they will always be prone to chronic infection, non-healing wounds, or higher parasite burdens. While Cushing’s disease is common and incurable, it can be very successfully managed. Horses that have well managed Cushing’s can continue their performance careers and live happy and relatively healthy lives for many years to come.