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Veterinarian Technician August 2009 (Vol 30, No 8)

Equine Essentials — Geriatric Horses — Maintaining a Good Quality of Life

by Carreen McCarthy, CVT

    Due to advances in veterinary care and nutrition, many horses are living into their twenties, thirties, or even forties. These animals fall into the category of a geriatric horse, defined as a horse greater than 20 years old. A recent study indicates about 7.5% of the equine population consists of horses over 20 years of age.1 Consequently, more and more owners are seeking veterinary care for elderly horses. As veterinary technicians, we are important members of the veterinary team caring for these special equine patients.

    General Care

    Elderly horses need special care and attention in order to provide them with a safe and comfortable environment. Subjects that we, as veterinary technicians, need to take into consideration when dealing with aged horses include: nutrition and feeding protocols, pasture environment, ambient temperature and grooming care, parasite control, dental care, common diseases of the geriatric horse, and euthanasia (see also Bentz AI, Bach C. Fare Thee Well: how to help owners (and yourself) deal with the death of a horse. Compendium Equine 2009; 4 (6): 267-273).

    Nutrition and Feeding Protocols

    The most important component of caring for geriatric horses is maintaining their body condition. Older horses often lose weight due to poor dentition, disease, parasites or due to competition with other pasture mates. It is important to take older horses' special needs into consideration to ensure they receive a well-balanced diet. An older horse may need special attention and supplemental feeding during months when there is less grass in the pasture. Geriatric horses also tend to suffer from osteoarthritis (OA), inhibiting them from grazing freely and thus reducing their intake of forage2 (Figure 1). It can be helpful to place hay in the pasture near the horses, so they may eat more easily. Sometimes the geriatric horse needs to be separated from the herd and fed in a stall to eliminate herd competition for food.

    It is important to note the overall body condition of an aged horse, and score the horse's body condition (see The Equine Scale). Body condition scoring is based on a scale from 1 to 9: 1 is extremely emaciated and 9 is extremely overweight (Figure 2). Horses that are either too thin or obese are prone to develop secondary diseases, such as hepatic lipidosis, when inappetant due to any reason. This condition is caused by a decrease in caloric intake causing fat to mobilize and accumulate in the liver. Horses with hepatic lipidosis may show clinical signs of lethargy, weakness, anorexia, decreased water intake, and diarrhea. Treatment is aimed at correcting the negative energy balance in the horse. This usually consists of administering intravenous (IV) fluids, nutritional support, and correcting the underlying disease (e.g., neoplasia). In addition, older horses will generally lose body condition in the winter or summer months when grazing is sparse. A careful history and examination of the feedstuffs will help delineate the cause of the horse's loss of body condition and identify ways to supplement energy intake.

    Aged horses may also have lost some of their teeth, have sharp edges on their teeth or a "wave mouth," leading to an impaired ability to chew hay, grain, or hay cubes. Specific dental conditions are discussed below; however, frequent teeth floating by a veterinarian will ensure good oral health and correct any defects that may impact a horse's ability to chew.

    Because of an increased parasite burden in the geriatric horse, decreased digestive efficiency and compromised chewing ability due to lack of teeth, we need to take special care when developing a feeding program for the aged horse. In general their feed should be palatable, easy to eat, and full of nutrients. Geriatric horses should be fed a senior diet giving small amounts of feed at a time. For example, small feedings three times a day is ideal. Senior feeds offer the horse increased protein, minerals, and vitamins. In addition to the senior feed, a ¼ to ½ cup of corn or vegetable oil may be added daily as an extra source of calories. Older horses are prone to weight loss, especially in the colder months, and require more calories to maintain their body condition. Soaked alfalfa cubes or pellets are also a good feed to offer older horses. Dengie hay is a good choice for older horses because it is less dusty, thereby minimizing any flare-ups of heaves, a disease that will be discussed later in this article.

    Pasture Environment

    As horses age, they often lose their place in the herd hierarchy and may be bullied by younger horses in the pasture. Therefore, it is a good idea to allow them time in the pasture alone or with another older horse. This will eliminate stress on the horse and allow them proper grazing time. Adequate pasture time is vital to minimize orthopedic issues and stiffness.

    Additional considerations include placing older horses in a pasture with a flat surface and monitoring weather conditions; they often have significant OA and may have stiffness and weakness in the hind-end, predisposing them to fall in slippery conditions such as severe rain, snow, or ice.

    Ambient Temperature and Grooming Care

    Geriatric horses are more sensitive to extreme weather conditions than younger horses.2 Older horses often have hirsutism (an overlong haircoat) and are often not able to thermoregulate correctly. They may also have areas of patchy sweating. Therefore, it is important to clip them, use blankets in colder weather, and to provide a cool environment during hot months. To improve circulation, daily brushing is advisable.

    Parasite Control

    Deworming and pasture management are important topics that veterinary technicians can address with owners. Implementing an effective deworming program is essential for proper barn management. Rotating dewormers ensures that various species and stages of parasites are killed. While geographic locations may differ in optimal deworming programs, deworming is generally recommended every 8 weeks. False negative results from fecal exams may be misleading, and while fecal egg counts are an important part of parasite control, they do not always detect encysted larvae, which can be detrimental to older horses. Using the proper larvicidal dewormer to kill encysted parasites and help maintain a good body condition in an older horse is important to overall good health of the horse. It is also important to remove manure routinely (e.g., once a week) and maintain a low stocking density of horses in the pasture.

    Dental Care

    Some of the dental abnormalities that affect geriatric horses include tooth loss, wave mouth, sharp points, hooks and broken or infected teeth (Figure 3). Wave mouth occurs when there is substantial difference in the height of several teeth. It should be easily seen or palpated on a dental exam, especially if the horse is sedated and an oral speculum is used. Geriatric horses also may suffer from smooth mouth, a condition where the occlusal surfaces of the teeth are smooth. These dental abnormalities can cause poor body condition because the horse is not able to chew properly. Horses with dental abnormalities will often drop grain or hay from their mouths while chewing, also known as quidding. Dental exams and teeth floating should be performed on geriatric horses every 6 to 12 months to be able to correct these conditions if necessary.

    Common Diseases of the Geriatric Horse

    The following overview addresses clinical signs, diagnosis and treatment of the six most common conditions affecting geriatric horses (see box).

    Pituitary Pars Intermedia Dysfunction (Equine Cushing's disease)

    With an increasing number of aged horses in the population today, there has been an increased awareness of diagnostic testing and treatment for Pituitary Pars Intermedia Dysfunction (PPID), commonly called Equine Cushing's-like disease. PPID is common in older horses and is caused by a malfunction of the pituitary gland, resulting in a tumor or enlarged gland.3 This leads to an increased secretion of pro-opiomelanocortin (POMC)-derived peptides and ultimately to the clinical signs listed below.

    A unique and consistent clinical sign of advanced PPID is the long, curly hair coat that does not shed or shed fully (hirsutism). Other clinical signs of horses with PPID include laminitis, muscle atrophy along the dorsum, fat accumulation, polydipsia, polyuria, secondary infections, lethargy, infertility, persistent lactation, hyperhidrosis, and metabolic abnormalities including hyperglycemia.3 Diagnosis is based on clinical signs and one of three tests: Dexamethasone-suppression test to assess cortisol response; serial measurements of ACTH, insulin, and dextrose; and thyrotropin-releasing hormone stimulation. However, none of these diagnostic tests are 100% accurate and while results are usually helpful, occasionally a false negative or false positive result can occur. Therefore, if the horse is older and exhibits these clinical signs listed above, PPID should be considered. Treatment is administration of pergolide PO q 24h for the remainder of the horse's life. In addition, careful management is vital to maintaining the horse's health, including clipping the haircoat and using a blanket during the winter months, and frequent trimming of the feet (e.g., every 4 weeks) (Figure 1).

    Laminitis

    Another disease that occurs in geriatric horses is laminitis, also known as founder. Laminitis is an inflammation of the laminae, causing degeneration and necrosis of the hoof.4 Because laminitis can be due to a plethora of diseases, the cause of this disease is not yet clear and is an active area of research by many universities. Laminitis can be an acute or chronic condition. Examples of diseases associated with acute laminitis include ingestion of large quantities of grain, strangulating intestinal lesions, or mares with placental retention. Chronic laminitis may be caused by diseases such as PPID; geriatric horses with PPID may develop laminitis as a secondary complication and it may even be the first indication that the horse has PPID. Clinical signs include lameness, depression, anorexia, and a horse's reluctance to move or lift its feet to be cleaned. Increased pulsations in the digital arteries can be palpated or sometimes visualized. Depending on the severity of the condition, the horse may stabilize with treatment; however, euthanasia is often recommended in severe cases4 (see AAEP Guidelines for Recommending Euthanasia, www.AAEP.org). Treatment is directed at the primary disease causing laminitis (e.g., administration of pergolide to horses with PPID), supportive care and pain management. It is important to keep the horse comfortable and supportive treatment includes shoeing changes, deep bedding in the stall, and nonsteroidal antiinflammatory drugs (NSAIDs). Also, these horses seem to have a higher rate of foot abscesses, which must be treated aggressively. It is important in these cases not to mistake laminitis for abscess formation and vice versa. Laminitis in non-PPID horses is often associated with a degree of third phalanx (P3) rotation, while horses with PPID often do not have rotation or only minimal rotation of P3 (Bertone, J. Personal communication, Dec. 2008).

    Heaves

    This disease is more appropriately known as Recurrent Airway Obstruction (RAO). A similar disease can occur in young horses and is known as Recurrent Airway Inflammation. It is a condition that can be acute or chronic and can affect a horse year-round or seasonally. Another form of the disease is actually worsened by outside exposure in the summer and on hot, humid days. Treatment includes keeping the horse inside in the heat of the day. This is commonly seen in the southeast United States, but is not limited to that region.

    Because a horse with RAO is reacting to an allergen in its environment (e.g., dust), care should be taken to minimize exposure to dust and known offending allergens. Providing adequate pasture time, minimizing dusty bedding and stalls, and soaking hay before feeding are important steps to alleviate RAO in the geriatric equine patient. Clinical signs include: cough, tachypnea, dyspnea, flared nostrils, wheezing, and a heave line, which is caused by increased exhalation and subsequent overdevelopment of external abdominal oblique muscles. Diagnosis is based on history, clinical signs, physical examination and diagnostic tests including transtracheal and bronchioalveolar lavage using an endoscope, radiographs, and blood tests. The most important part to controlling RAO is minimizing allergens and dust in the horse's environment.

    Uveitis

    Equine recurrent uveitis, also referred to as moon blindness, is one of the most common ocular diseases of the horse and the most common cause of blindness in equine patients.5 It is an immune-mediated disease characterized by periods of inflammation and inactive periods where inflammation may be difficult to discern. Clinical signs include photophobia, swelling and reddening of the conjunctiva, excessive tear production or discharge from the eye, corneal edema, and constriction of the pupil (miosis).6 Uveitis can be the result of trauma to the eye or caused by systemic disease including leptospirosis, brucellosis, onchocerciasis, strangles, equine influenza, or tooth abscessation.5 The diagnosis of uveitis includes a thorough ophthalmic exam and additional diagnostic tests, such as a CBC and serum chemistry panel. Treatment is based on the underlying clinical disease and use of topical and systemic antiinflammatory and antimicrobial medications to reduce intraocular inflammation and further damage to the eye. If the condition is chronic, sometimes surgical intervention may involve vitrectomy (removal of the vitreous) or a suprachoroidal cyclosporine implantation in which a cyclosporine disk is implanted under the scleral flap. It is important to treat uveitis quickly because recurrent episodes can lead to other chronic conditions such as adhesions between the iris and the lens, cataracts, retinal degeneration and, most importantly, blindness.

    Euthanasia

    As always, the subject of euthanasia can be difficult to discuss with an owner. Many times these horses have been members of the family for several decades. As veterinary technicians, we need to recognize the bond between owners and their horses and understand the loss they are feeling. We can help provide compassion and support at a time when they are needed the most.7

    When the owner decides to euthanize his/her horse, some medical issues need to be taken into consideration. Whether the veterinarian chooses to use a needle or insert a catheter, it is helpful to clip the area over the jugular vein. As with any aged animal, these horses can be thin and it can be difficult to locate the jugular vein. Due to the large size of these animals, disposal also can be a concern. The owner may choose to bury or cremate the horse. If burial is elected, the owner should contact local authorities because of possible restrictions in their township.

    Geriatric horses are treasured members of the owner's family and have unique needs. When veterinary technicians understand the needs of these special horses, we can better educate the client and improve the lives of geriatric horses.

    1. Part I: Baseline Reference of 1998 Equine Health & Management. Washington, DC: USDA:aphis, 1998; 7, 9, 12, 21, 44-46.

    2. Ralston SL. Management of Geriatric Horses. Available at www.ker.com, October 2008.

    3. McFarlane D: Pituitary and Hypothalamus, in Smith, BP (ed): Large Animal Internal Medicine, ed 4, St. Louis, MO, Mosby Elsevier, 2009, pp 1340-1344.

    4. Linford, RL: Laminitis (Founder), in Smith, BP (ed): Large Animal Internal Medicine, ed 4, St. Louis, MO, Mosby Elsevier, 2009, pp1224-1227.

    5. Equine Uveitis, in Aiello SE, (ed): The Merck Veterinary Manual, ed 8, Whitehouse Station, NJ, Merck & Co., Inc., 1998, pp 360-362.

    6. Slater JD: Medical Nursing, in Coumbe, K (ed): Equine Veterinary Nursing Manual Oxford, UK, Blackwell Science Ltd, 2001, pp 249-283.

    7. Bentz AI: The Geriatric Horse, in McCurnin DM, Bassert JM, (ed): Clinical Textbook for Veterinary Technicians, ed 7, Philadelphia, PA, Elsevier, 2009.

    References »

    NEXT: Final View — Insatiable Hunger

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