The pituitary gland is a normal part of the typical mammalian brain, sitting at the base of the brain just above the two optic nerves (one from each eye). There are three lobes in the pituitary gland – one of which is the “pars intermedia.” For reasons unknown, the cells in this region begin to increase in size, increase in number, and/or change into a benign tumor – called an adenoma. This underlying change seems to be the primary contributor to Cushing’s disease in the horse, which is different from, say, a dog, who may develop Cushing’s due to a problem in the pituitary gland or the adrenal gland.  The pituitary gland, in both species, regulates the adrenal glands’ production of cortisol (commonly known as adrenaline). It is primarily the effects of cortisol that result in the symptoms seen with PPID.

Symptoms of PPID can vary based on the stage of the disease and specific proteins that are being overproduced by the horse’s pituitary gland. The average age is 20 years, but horses 7 years or older can develop the disease. Ponies and Morgans have a high incidence of the disease. The most commonly recognized sign of PPID in horses is a long, curly hair coat with abnormal shedding patterns.  Another common sign is excessive drinking (considered >25-30L (8-10 gallons) in the normal horse) and/or urination.  Bulging eyes, abnormally located fat deposits, inappropriate lactation, muscle atrophy, and/or weight loss may also be seen. Related problems that can occur in horses with PPID include laminitis, fertility problems, chronic infections or recurrent hoof abscesses, and blindness.  Blindness in horses may occur when growth of the pituitary gland results in compression of the optic nerves.

There is more than one way to diagnose Cushing’s disease in your horse. The “gold standard” test is called the Dexamethasone Suppression Test – it is considered the most reliable.   The horse is given an injection of dexamethasone, a type of steroid.  Then a blood sample is taken approximately 18-20 hours later.  If the horse is not able to reduce his own level of cortisol in response to the steroid we injected (“doesn’t suppress”), he is considered positive for Equine PPID.  This test can be performed with the horse in-hospital overnight, or with two farm call visits. The other test for Equine Cushing’s is a baseline ACTH measurement (a hormone that is produced by the normal and abnormal pituitary). If, at rest, the ACTH is above a certain level, it can be presumed that the excess production is a result of PPID.  These are the two most reliable and commonly performed diagnostic tests for Equine PPID.

While treatment of PPID is not curative, it can significantly improve your horse’s quality of life, ability to fight off infections, and potentially fertility in older broodmares. The most effective treatment for Equine PPID is pergolide powder, given by mouth as a top-dress to feed or via syringe once daily. Sometimes the initial dose of pergolide must be adjusted to fit your horse’s disease severity and response – repeating the above diagnostic tests once your horse is started on pergolide treatment can help determine if the given dose is appropriate. Pergolide treatment costs about $80 per month, and is given for the remainder of the horse’s lifetime. While expensive, it may reduce your horse’s future discomfort, and your future medical expenses related to management of laminitis, chronic infections, or infertility. Other treatment options include cyproheptadine, which is generally less expensive, but seems to show less consistent benefits than what has been seen in studies when compared with pergolide. It has been used in combination with pergolide for the purpose of improving its efficacy. Other important aspects of treatment and management of PPID in horses include a good preventative medicine program (vaccines, deworming, dentals), clipping of the long hair coat in summer, management of infections with antibiotics, corrective farriery for laminitis and hoof abscesses, and maintaining a good body condition with an appropriate feeding schedule.

If you suspect your horse may be affected with Equine PPID, and are interested in diagnostic testing and/or treatment, please contact the office to schedule an appointment. For any further questions about this newsletter, feel free to contact Dr. Lacher or Dr. King by phone or email.

The defnition of senior or geriatric horse is very individual dependent.  Some of our patients are slowing way down at 18 to 19 years, others are being ridden 3-4 times per week and even still showing in to their late 20s.  Many factors determine how your horse handles the years but diet, exercise history and genetics are very strong components.

I drew from some human research to determine that the biggest reason we slow down as age is fat.  Young adult humans are at maximum muscle mass which slowly declines over the years and is replaced by fat.  Nerve conduction velocity decrease and we lose some ability to move oxygen from our lungs to our tissues.  But I said slow down, not stop.  This means many older horses can continue to compete, trail ride or whatever you wish.

The type and extent of conditioning primarily will depend on several factors, including the age of the horse, training history, body condition, and the main goal of the conditioning program. For example, the amount of training that is reasonable for a 15-year-old horse will likely be considerably greater than for a horse in his mid-20s. However, regardless of age, we need to consider the horse’s training history carefully. There are many eventers, show jumpers, and endurance horses which have sustained a high level of fitness throughout their teen years–those horses appear capable of training and competing at a level not far below that of a much younger horse. However, because they are well-schooled in their respective events, these seasoned campaigners often can remain competitive with a lower training volume. This helps reduce excessive wear and tear on the musculoskeletal system.

The situation will be much different for the middle-aged and older horse which has received little exercise for a number of years. A much more cautious approach to conditioning is required.  As well, there is an impression among riders and trainers that those horses take more time to attain fitness compared to the youngsters.  Therefore, you must start out very gradually, be patient, and closely monitor your horse for signs that indicate you are overdoing it.  For horses of any age, injury and lameness can occur when the training volume is increased rapidly.  Carefully palpate tendons and ligaments of the lower limbs for signs of heat, swelling, and pain.

Obviously, the level of training also will depend on whether or not you are aiming to compete your horse. This is a reasonable goal for the teenager, but (in most cases) less reasonable for the horse in his mid-20s. More realistic is a program of regular light exercise that helps maintain body condition and muscle tone, and allows the horse to be used for trail riding or similar tasks. This is a win-win situation–regular exercise will help prevent or even reverse some of the age-related changes in muscle mass and strength, and will also improve your horse’s quality of life. Daily turnout is another way to ensure that the horse receives regular exercise, and is certainly important for maintaining good spirits.

The most common limiting factor in older horses is chronic lameness.  It’s a good idea to have one our Doctors examine your older horse before putting the previously idle horse back into work. Lameness associated with foot pain is common in older horses, and some medication as well as special shoes might be necessary.  Pain associated with degenerative joint disease is common; again our Doctors will be able to identify these problems and make recommendations concerning pain relief and exercise programs.

It is advisable to schedule regular veterinary check-ups, particularly for horses in their 20s. Keep a close eye on the joints, tendons, and ligaments of the legs–any stiffness or swelling might signal the recurrence of an old problem and the need to moderate the conditioning program.

Start your conditioning program slow.  Monitor your horse’s response to increased work very closely.  As a guide, do not increase the weekly training distance by more than 5%. Three 10-15 minute sessions per week on the longe line or under saddle might be an appropriate place to begin–the length of these workouts can be increased over the next month. Then, you can add another weekly session and/or begin to increase the intensity of the workouts gradually by inserting some low-speed cantering. Try to vary the workouts as much as possible to maintain the horse’s interest. If possible, include a little hill training–this will help muscles strengthen.

Be cautious during the hot summer months, particularly when beginning training during the summer.  Older humans and animals are often less able to lose body heat during exercise, in part because of a decline in cardiovascular performance and a reduction in sweat gland function.  For that reason, it is wise to limit exercise on very hot days–either shorten the duration of work or reduce the intensity of exercise. In hot weather, actively cool the horse after exercise by applying cold water over the neck and body.  Also allow him to drink a moderate amount of water after exercise to replace fluid losses due to sweating.

Watch your older horse’s weight while increasing workloads.  Some older horses can have trouble absorbing nutrients from their feed.  If your horse is having trouble maintaining weight with an increased work load consider switching to a Senior diet.  With their easily digestible nutrients and higher fat content they are the perfect choice.  Additional fat in the form of vegetable oil can also be added to increase weight.

Hope these guidelines help you keep your older horse in work!

The defnition of senior or geriatric horse is very individual dependent.  Some of our patients are slowing way down at 18 to 19 years, others are being ridden 3-4 times per week and even still showing in to their late 20s.  Many factors determine how your horse handles the years but diet, exercise history and genetics are very strong components.

I drew from some human research to determine that the biggest reason we slow down as age is fat.  Young adult humans are at maximum muscle mass which slowly declines over the years and is replaced by fat.  Nerve conduction velocity decrease and we lose some ability to move oxygen from our lungs to our tissues.  But I said slow down, not stop.  This means many older horses can continue to compete, trail ride or whatever you wish.

The type and extent of conditioning primarily will depend on several factors, including the age of the horse, training history, body condition, and the main goal of the conditioning program. For example, the amount of training that is reasonable for a 15-year-old horse will likely be considerably greater than for a horse in his mid-20s. However, regardless of age, we need to consider the horse’s training history carefully. There are many eventers, show jumpers, and endurance horses which have sustained a high level of fitness throughout their teen years–those horses appear capable of training and competing at a level not far below that of a much younger horse. However, because they are well-schooled in their respective events, these seasoned campaigners often can remain competitive with a lower training volume. This helps reduce excessive wear and tear on the musculoskeletal system.

The situation will be much different for the middle-aged and older horse which has received little exercise for a number of years. A much more cautious approach to conditioning is required. As well, there is an impression among riders and trainers that those horses take more time to attain fitness compared to the youngsters. Therefore, you must start out very gradually, be patient, and closely monitor your horse for signs that indicate you are overdoing it. For horses of any age, injury and lameness can occur when the training volume is increased rapidly. Carefully palpate tendons and ligaments of the lower limbs for signs of heat, swelling, and pain.

Obviously, the level of training also will depend on whether or not you are aiming to compete your horse. This is a reasonable goal for the teenager, but (in most cases) less reasonable for the horse in his mid-20s. More realistic is a program of regular light exercise that helps maintain body condition and muscle tone, and allows the horse to be used for trail riding or similar tasks. This is a win-win situation–regular exercise will help prevent or even reverse some of the age-related changes in muscle mass and strength, and will also improve your horse’s quality of life. Daily turnout is another way to ensure that the horse receives regular exercise, and is certainly important for maintaining good spirits.

The most common limiting factor in older horses is chronic lameness.  It’s a good idea to have one our Doctors examine your older horse before putting the previously idle horse back into work. Lameness associated with foot pain is common in older horses, and some medication as well as special shoes might be necessary. Pain associated with degenerative joint disease is common; again our Doctors will be able to identify these problems and make recommendations concerning pain relief and exercise programs.

It is advisable to schedule regular veterinary check-ups, particularly for horses in their 20s. Keep a close eye on the joints, tendons, and ligaments of the legs–any stiffness or swelling might signal the recurrence of an old problem and the need to moderate the conditioning program.

Start your conditioning program slow.  Monitor your horse’s response to increased work very closely.  As a guide, do not increase the weekly training distance by more than 5%. Three 10-15 minute sessions per week on the longe line or under saddle might be an appropriate place to begin–the length of these workouts can be increased over the next month. Then, you can add another weekly session and/or begin to increase the intensity of the workouts gradually by inserting some low-speed cantering. Try to vary the workouts as much as possible to maintain the horse’s interest. If possible, include a little hill training–this will help muscles strengthen.

Be cautious during the hot summer months, particularly when beginning training during the summer. Older humans and animals are often less able to lose body heat during exercise, in part because of a decline in cardiovascular performance and a reduction in sweat gland function. For that reason, it is wise to limit exercise on very hot days–either shorten the duration of work or reduce the intensity of exercise. In hot weather, actively cool the horse after exercise by applying cold water over the neck and body. Also allow him to drink a moderate amount of water after exercise to replace fluid losses due to sweating.

Watch your older horse’s weight while increasing workloads.  Some older horses can have trouble absorbing nutrients from their feed.  If your horse is having trouble maintaining weight with an increased work load consider switching to a Senior diet.  With their easily digestible nutrients and higher fat content they are the perfect choice.  Additional fat in the form of vegetable oil can also be added to increase weight.

Hope these guidelines help you keep your older horse in work!