The good news is that today's canines are living longer. Senior dogs make up about 39 percent of the total dog population. A dog's advancing age signals owners to begin more frequent check-ups to the veterinarian. For large and giant breeds, these visits should begin at earlier ages.
Geriatric examinations are intended to catch signs of disease early so treatment can begin while it is cost-effective and easier for the dog. A geriatric physical screening, including a nutrition evaluation, can help determine how well a dog is coping with aging and whether a change in management or diet are needed.
Here, we examine four age-related health problems and look at how adjusting dietary nutrients can contribute to effective management. Before making a diet change, you should consult your veterinarian.
Chronic Kidney Disease
Chronic renal failure, which occurs gradually over weeks to years, is the most common type of canine kidney problem. A vital organ for the dog, the kidney controls levels of metabolic breakdown products, electrolytes and other products of metabolism in the blood by excreting excesses in the urine. When the kidney fails, these substances can build to damaging levels.
The kidney also helps the body maintain a sufficient level of important substances such as water, minerals and B vitamins. Without the kidney's assistance, these substances would escape the body. As a result, dogs with kidney disease can become dehydrated and develop certain vitamin deficiencies.
The initial symptoms of kidney disease often are subtle. A dog might become lethargic, show a change in eating habits, have mild weight loss or have increased urination and drinking. As the disease progresses, symptoms can become severe and include vomiting, diarrhea, ulcers in the mouth, depression, loss of appetite and more dramatic loss of weight.
When a dog with kidney disease loses weight, metabolic changes generally occur that cause it primarily to lose muscle, which affects strength. Disease management focuses on minimizing clinical signs and slowing the progression to end-stage renal failure.
Dietary management is an important part of treatment. For many years, the practice has been to focus on controlling protein intake, because the clinical signs of kidney failure often are attributed to problems processing byproducts of protein metabolism.
Maintaining a moderate-protein diet in dogs with kidney failure is helpful. One study found that dogs responded well on moderate-protein diets, containing from 20 to 31 percent of energy from protein.1 In contrast, dogs on low-protein diets of 7 to 9 percent of energy and high-protein diets of 38 to 49 percent of energy showed poor responses.
Recent research has attempted to separate the impact of dietary protein from dietary phosphorus. Phosphorus is an essential nutrient for dogs; however, because the kidney is responsible for excreting excess phosphorus, kidney failure can cause a build up of phosphorus in the blood. High phosphorus levels contribute to progression of kidney disease and may cause other complications.
A study of the effect of dietary phosphorus and protein in dogs with chronic renal failure found that dietary phosphorus restriction was important for reducing renal failure and enhancing survival, while protein restriction provided no benefit.2 Phosphorus-restricted diets, less than 0.4 percent, should be used as needed to help maintain a normal serum phosphorus concentration.
Congestive Heart Failure
Coughing, respiratory distress, restlessness at night or exercise intolerance typically are the first signs of congestive heart failure in dogs. As the disease progresses, therapy generally consists of pharmaceuticals along with rest, oxygen and dietary sodium restriction.
While sodium generally is restricted, potassium and magnesium may need to be supplemented. Potassium is required for body fluid, nerve transmission and certain metabolic processes, and magnesium helps to regulate the movement of ions across cell membranes. Dogs with respiratory or metabolic complications sometimes have artificially elevated serum potassium, which masks or even contributes to chronic potassium depletion. Deficiencies in both potassium and magnesium may contribute to cardiac arrhythmias in dogs.
Obesity can contribute to or aggravate heart disease and should be addressed to reduce the workload on the heart. Obese animals have shown pronounced improvement in cardiac performance following weight loss.
Veterinarians may suggest that dogs be fed several small meals to help enhance intake and reduce gastrointestinal upset. Highly digestible, high-calorie diets are usually recommended to enhance calorie absorption and to minimize protein breakdown. Excessive protein restriction could contribute to cardiac wasting. Depending on the treatment or medications prescribed by the veterinarian, he or she may also advise that a dog with heart disease be given a vitamin and mineral supplement to help compensate for losses induced by the medications.
Obesity
Approximately 25 percent of dogs seen by veterinarians in the United States are overweight or obese.4 Effective obesity management can help reduce musculoskeletal problems, compromised immune function, abnormal glucose tolerance, heat or exercise intolerance, and complications from cardiovascular or other diseases.
Use of a body condition score system can aid in monitoring weight by providing an indication of the correct proportion of fat and lean mass.5 By recording both body weight and body condition score, a dog's ideal body weight can be more easily determined. Dogs that are becoming obese can be recognized sooner and managed more easily.
Almost any nutritionally complete and balanced diet can be used for weight loss, since the key is to reduce calorie intake below calorie expenditure. Low-calorie, high-fiber foods formulated for weight loss contain nutrient levels adjusted for calorie restriction; however, calorie restriction with a low-fat, high-protein diet is more effective for loss of body fat than a high-fat diet, despite similar calorie restriction.6,7 These diets provide normal amounts of protein and other nutrients while decreasing fat and calories. Additionally, the fiber in these products may provide a satiety effect.
Reducing or eliminating table scraps or other high-fat foods, feeding measured amounts rather than free feeding, increasing activity or switching to a lower calorie dog food also should help control weight in obese dogs. If possible, feed several times a day. Feeding increases the metabolic rate, so feeding the same number of calories in four meals instead of one will reduce the number of usable calories,8 aiding in weight loss.
There are numerous components of an effective weight loss program. Most deal with diet and how it is fed, the inclusion or exclusion of treats, and the type and amount of exercise to provide. Gradual weight loss in dogs is more successful with long-term maintenance of the reduced body weight.9 Weight rebound can be minimized by providing controlled food intake and adjusting the calories to meet the needs of the dog for weight maintenance.
Problems Gaining Weight
Weight loss is not unusual in older dogs. In fact, a greater proportion of older dogs are underweight than any other age group.4 Decreased food intake can occur for many reasons, and dietary modifications vary for underweight dogs. A high-carbohydrate, low-fat diet may be effective when weight loss is due to pancreatic exocrine insufficiency, lymph disease or liver disease with fat malabsorption, but not for weight loss due to poor appetite or feeding management problems.
For example, when dogs are fed together, pack relationships sometimes change with age and time. An evaluation of group behavior may indicate that a dominant dog has been displaced and is no longer receiving free access to a common food bowl.
If poor appetite is a problem, an owner could try selecting a more palatable diet; moistening dry food; warming food to body temperature; offering fresh food frequently; and petting and encouraging the dog during feeding. It also might help to minimize noise and stress during feeding.
Poor dental health also could prevent an otherwise healthy dog from consuming adequate nutrition. Dry foods help reduce the buildup of plaque and tartar on teeth, but soft foods may be needed following extensive tooth loss for some dogs.
If food intake is normal or increased but a highly active dog has been fed a commercial senior diet or reduced-calorie diet, weight loss could be a normal response. The dog may have unusually high energy needs due to individual metabolism or lifestyle.
Most geriatric diets are designed for low-calorie density and are not appropriate for dogs with weight management problems associated with weight loss. Nutrient-dense foods formulated for older pets would be appropriate. Other reasonable choices include products formulated as critical care or stress diets or those for growing puppies.
If recent diet changes precipitated a dog's weight loss, consider offering the previous diet. If other reasons for weight loss are excluded, a dog should be evaluated for signs of cancer or intestinal, kidney or pancreatic disease.
Practicing Prevention
It is never too late to start practicing good nutrition and health care with your dog. Ideally, the process begins with the puppy. By introducing good nutrition at an early age, owners can effectively delay the onset of many age-related health problems.
However, an older dog can have turnaround results when a proper diet is introduced to match its nutritional needs. Other factors that contribute to raising a healthy senior dog include avoiding stress, keeping your dog active and closely monitoring changes. Above all, take time to share experiences and enjoy your dog.