Words Carole Sandhu BSc (Hons) MSc RD – Companion Animal Nutritionist
Many pet parents will agree that living with a healthy, older dog is an absolute pleasure. They are often well behaved and enjoyable to live with and of course we know all their funny little habits and they know ours even better! As cherished family members, we want long and healthy lives for our dogs. What is exciting is that by meeting their specific nutritional needs we may be able to extend their health and well-being beyond current limits.
The ageing process
Dogs are ageing in parallel with the human population, with around 40% of dogs aged 7 years or more. Interestingly, dogs do not age consistently, and chronological age does not always match physiological age. For example, in small breeds, a higher lifespan is expected than with larger breeds, especially the giant breeds. In large dogs, old age starts earlier compared to small breeds dogs of the same chronological age. Commonly, large breed dogs are classified as senior from the age of 5-8 years, small breed dogs from the age of about 10 years.
As our dogs get older, some of the changes we may notice such as a few grey hairs or a slightly reduced activity level have no impact on health. However, the deteriorative changes that may negatively affect a senior pet’s overall health and quality of life, such as those associated with illness, changes in mobility, changes in cognitive function and the development of behavioural problems are referred to as senescence.
While few diseases are diet induced with the exception of obesity, many other diseases are diet-sensitive, meaning that diet can play a role in managing the condition. Examples of diet-sensitive conditions include chronic renal disease, diabetes mellitus, and arthritis. Other changes may impact on food intake and subsequent nutritional status such as gum disease, tooth loss, reduced appetite and food intake and changes in taste and smell. These are all important factors to consider when planning how best to support the nutritional needs of older dogs.
The nutrient requirements of older dogs
As ageing is a slow process, it is not always obvious as to when the best time is to make changes to the diet and so regular monitoring and body condition scoring is essential. Once we decide the time is right to make changes the major objectives are to maintain health and optimal body weight, slow or prevent the development of chronic illness, and minimise or improve clinical signs of diseases that may already be present.
At present, there are no specific recommendations for energy or nutrient requirements for older dogs. For optimal feeding, the following can be as useful guide to ensuring their nutritional needs are met.
The most consistent nutritional change with age in dogs is gradual decline in energy (calorie) needs. By 7 years of age their energy needs are slightly lower, but by 11 years of age energy needs can reduce to three quarters of what they were as a younger adult. This is a result of the combination of reduced lean mass (muscle), general daily energy needs (basal metabolic rate) and body temperature, along with an increase in subcutaneous fat storage. That said, the lifestyle of the dog can have a big effect on these changes and working/sporting dogs who remain active continue to have the same energy needs as they did when they were younger.
Dogs should ideally be weighed regularly, and their feed adjusted accordingly. In general, inactive dogs or those that are overweight would benefit from foods specially formulated to have an increased nutrient to calorie ratio. This means their food portion sizes will be significant enough for them to feel satisfied after a meal. In contrast, if they remained on a standard feed formulated for younger dogs, they would need a small portion to meet their energy needs which may leave them feeling hungry between meals as well as only obtaining a reduced amount of essential nutrients. Dietary protein is especially important in weight loss diets. Providing low calorie diets with increased protein-calorie ratio significantly increases the percentage of fat lost and reduces the amount of loss of lean body mass. On the other hand, senior dogs are often underweight, perhaps due to taste changes, illness or poor dentition, so feeding a highly palatable food with a high energy density such as a soft wet food option will help to maintain a healthy weight in these cases.
Where a dog has a reduced appetite, diets should contain a higher protein concentration to meet their needs and delay age related loss of lean body mass, except when specific diseases require adjustments of protein level. The protein should be of good quality (human grade meat) so that it supplies sufficient levels of essential amino acids. The level of crude protein in the diet should be 15% to 23% dry matter for healthy senior dogs.
Older more sedentary dogs can become constipated so increasing dietary fibre can be an advantage. The addition of fibre can also help to reduce the energy density of a diet formulated for overweight senior dogs. Crude fibre in the diet should be at least 2% dry matter for healthy senior dogs.
In some older dogs, chronic weight loss can be a problem, perhaps because of reduced appetite, so increasing the energy density of the diet by increasing the fat content can help to maximise the energy (calories) in the smaller portion they can manage. Fat also improves palatability and protein metabolism (protein sparing effect). This means the dietary protein is used for growth and repair rather than a source of energy which is of particular benefit to the older dog. The level of crude fat in the diet should be 7% to 15% dry matter (or 7% to 10% dry matter for obese dogs).
Given the prevalence of chronic renal disease in older dogs, ongoing medication such as diuretics chronic dehydration is a potential risk. There should always be plenty of fresh, clean water available and ideally owners should be monitoring the dog’s consumption.
The increase in oxidative stress with age is an important factor in the process of ageing, but oxidative stress can be offset, to a degree, by increasing the levels of key antioxidant precursors in the diet. Glutathione peroxidase is an important antioxidant in this regard, and its precursors are vitamin C, vitamin E and selenium. Therefore, even though the dog can make his/her own vitamin C, it is beneficial to have it in the diet for its antioxidant potential.
Fortunately, osteoporosis does not occur in elderly dogs compared to elderly humans so increasing levels of calcium in the diet above the required level for adult dogs is not necessary.
About 25% of older dogs have some degree of renal impairment, which may be sub-clinical (no clinical signs apparent) phosphorus in the diet should be restricted in these cases on the advice of your Vet.
Sodium levels of more than 2% dry matter found in some commercial diets is too high for senior dogs with chronic renal or cardiac disease.
Once we have the right nutrient balance which suits the older dog, a few tweaks to the feeding schedule can ensure optimal intakes. It is recommended that older dogs should be fed at least two or three small meals per day rather than one large meal. Feeding several small meals per day promotes improved nutrient use and may decrease feelings of hunger between meals.
Dogs with a chronic disease should be fed a diet that is appropriate for the management of the disorder.
In summary, regular monitoring of the body condition and weight can tell us when the time is right to make some changes to what we feed. Healthy older dogs can be fed a diet that contains high-quality ingredients, moderate to high levels of high-quality protein and moderately reduced amounts of fat. Other nutrients that may be beneficial include increased levels of antioxidant nutrients. This will help our most cherished canine companions maintain health and well-being well into their senior years.
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