Aging gracefully--feeding senior pets (Proceedings)

General feeding recommendations for pets

With the hundreds of pet foods available today, an owner's decision about what to feed his or her pet has become a more complicated question than it once was. Nor is there one simple answer since the "best" food for a pet depends on many factors, such as life stage, body condition, exercise (or lack thereof), environment, and health status. Often, owners base their decisions on marketing, rather than on objective nutritional information.  Although there are limitations to the information provided on a pet food label, the label can provide important information to help in selecting foods.  Below are some common questions from owners about pet foods.

What is the best food to feed my pet?

There is no best diet, despite all the marketing claims to the contrary. Every pet is unique and the goal is to find the best diet for the individual pet. Expense doesn't necessarily equal quality. There are some inexpensive diets that have years of rigorous scientific testing behind them and some very expensive diets that are lacking in vital nutrients or based on unsound science. Larger companies generally have more stringent quality control protocols, employ expert nutritionists and food scientists, and strive to increase our collective nutrition knowledge through research. Smaller manufacturers may have less control over ingredient quality, perform less laboratory testing and are less likely to employ full or part time veterinary nutritionists.

A good rule of thumb is that if the marketing of a product sounds too good to be true, the manufacturer cites studies or research that they cannot provide to you or makes claims that cannot be substantiated, then that's a red flag that the diet should be avoided.

How can I pick a good diet to feed to my pet?

Consumers should look for foods made by reputable companies with long histories of producing quality diets. Diets that have an Association of American Feed Control Officials (AAFCO) statement on the label saying that the diets have undergone animal feeding trials for the appropriate life stage are generally preferable to diets that are formulated [by computer] to meet AAFCO nutrient profiles for that life stage. This distinction is particularly important for puppy and kitten diets as well as diets produced by newer and smaller companies with less experience in diet formulation.

Ideally, manufacturers should be engaging in both internal and external (such as through a university) research to both improve their products and increase our collective nutrition knowledge. Advertisements and websites should not contain unverifiable claims, perpetuate nutrition myths or promote products solely by bashing other manufacturers' products. In addition, the diet owners select for their pets should be one that the animals do well on.

Is the ingredient list a good way to determine the quality of a pet food?

Although ingredient lists are commonly used by lay people to determine the quality of pet foods, this approach has many pitfalls and is very subjective to intentional manipulation by the food manufacturers. Ingredients are listed on labels in order of weight, including water, so ingredients with high water content (like fresh meats and vegetables) are going to be listed higher than similar amounts of dry ingredients even though they may contribute fewer nutrients to the overall diet. Additionally, ingredients from the same source-chicken meat, chicken fat and chicken by-product meal for example-can be split into component parts, further complicating assessment.

Pets require nutrients, not ingredients; a diet full of great sounding ingredients can be less nutritious than a diet containing less appealing (to people) ingredients. Some manufacturers may add ingredients to diets solely for marketing purposes, to increase the appeal of the diet to consumers. These ingredients may have unproven benefits, be present in miniscule amounts and provide nothing to the diet but added expense. More ingredients also mean more quality control (and more time and expense) is necessary to ensure that the finished product adheres to the desired nutrient formulation.

It is also important to understand that the phrase human grade has no legal meaning in the pet food industry. Once a product is destined for inclusion in pet food, it is no longer fit for human consumption by definition. Moreover, ingredients sourced from the human food chain are not necessarily any more nutritious, wholesome, or safe than ingredients initially destined for pet food. Therefore, manufacturer's claims of human grade ingredients should not be over interpreted.

I've heard that raw diets prevent and or solve a lot of health problems in pets. Is this true?

Despite anecdotal reports from pet owners and even some veterinarians, there is currently no evidence that raw diets offer any benefits over cooked diets. However, there is substantial evidence that these diets may be associated with dental fractures, bacterial and parasitic infections and other health concerns in pets. There is also potential risk to people, especially those that are immunocompromised such as young children, the elderly and patients with immune mediated diseases or cancer. Pets that eat contaminated raw diets have been demonstrated to shed viable pathologic organisms in their feces and it is likely that areas that they frequent are also contaminated. As numerous recalls and some pathogen surveys in the last few years have proven, all raw meat, regardless of source, should be considered to be contaminated until proven otherwise. For these reasons, the Delta Society has banned raw fed pets from participating in their pet therapy programs.

In addition to food safety concerns, nearly all home-prepared raw diets and most commercially available raw diets are deficient (or excessive) in essential nutrients. It is also common for commercial raw diets to be very high in fat, which may not be tolerated by some animals.

My friend says that grains are bad for dogs, is she correct?

Whole grains, rather than being fillers, contribute valuable nutrients including vitamins, minerals, essential fatty acids and fiber to diets while helping to keep the fat and calories lower than if animal products were used in their place. Even refined grains such as white rice can have beneficial health implications depending on the type of diet and the pet. The vast majority of dogs and cats are very efficient at digesting and utilizing nutrients from grains. While a very small number of dogs are allergic to specific grains, these allergies are no more common than allergies to animal proteins such as chicken, beef and dairy and tend to reflect the prevalence of the ingredient in commercial diets rather than enhanced antigenicity.

It is becoming more common in the saturated pet food market for manufacturers to perpetuate myths to sell diets and increase market share. Grain-free diets are often an example of this strategy. Many of these diets merely substitute highly refined starches such as those from potatoes or tapioca (cassava) in place of grains. These ingredients often provide fewer nutrients and less fiber that whole grains, while costing more.

I read online that by-products can contain hair, hooves and floor sweepings. Is this true?

By-products are commonly vilified, often by diet manufacturers trying to carve out market share for themselves by offering diets that do not contain them. By-products (mainly organ meats and entrails) often provide more nutrients than muscle meats on a per weight basis and are important components and even delicacies of human diets in other countries. The term by-product comes from the fact that they are the leftovers from animal carcasses once the desirable (for Americans) muscle meat has been removed. AAFCO definitions of mammal by-products specifically exclude hair, hooves, horn, hide trimmings, manure and intestinal contents, as well as anything that is not specifically part of the carcass (such as floor sweepings). Like all ingredients, the quality of by-products can vary, so it is important to select manufacturers who have stringent internal quality control standards.

Can I use the guaranteed analysis to accurately compare pet foods?

The guaranteed analysis is required to give only the minimum content of protein and fat in the food and the maximum content of fiber and moisture.  Other nutrients may also be listed but are not required.  This obviously is only a limited number of nutrients you might be interested in and, in addition, having the minimum or maximum level of a nutrient might not provide all the information you need (for example, in a dog that requires dietary fat restriction, a minimum fat level of 3% listed on the label does not tell you exactly how much fat the diet contains (it might contain 3% but it might contain much more). 

Another issue that commonly confuses pet owners is that the nutrient levels in the guaranteed analysis are listed on an "as fed" basis, which includes the water in the food (therefore, the protein level of a dry food will appear to be much higher than the protein level in a canned food, even if the levels on a dry matter basis are exactly the same). A much more accurate way to compare foods is to compare them on a gram or milligram per 100 kcal basis.  This information should be available from the manufacturer whose name and address must be listed on the label.  The contact information for the manufacturer is one of the most useful pieces of information on the label. A company should be able to provide any other nutritional information that you might require for your patients.  If a company cannot or will not provide you with a piece of nutritional information, I would consider that to be a red flag and would not recommend that food!

Can I feed my pet according to the feeding directions on the label?

Pet food labels must list feeding directions.  Many feeding guidelines overestimate the amount a dog or cat should eat (although some of the pet food companies are beginning to revise their labels to contain more reasonable estimates).  Therefore, feeding directions should be used only as a starting point and owners must make adjustments to keep the pet in trim body condition.  I typically recommend that owners start at the lower end of the recommended range for most animals (even lower if they have a low activity level) and then carefully monitor body weight for the first several weeks on the new diet so that adjustments can be made as needed.

It seems obvious that the calorie content of the food would be on the label but this is not required information (except for "light" foods).  The calorie information is allowed on the label and some pet food companies are starting to include the calorie content.  This is very helpful information to be able to compare foods. There are maximum caloric densities for foods that are described as "light," "lite," or "low calorie" (for example, a dry dog food must contain < 3100 kcal/kg).  In addition, when a food is described as such, the label must contain a calorie content statement.  However, these food still vary tremendously in terms of the calories per cup or can so one must be careful to select one that is appropriate in calorie and nutrient level for the individual pet.

Should I try to feed a natural or organic pet food?

The guidelines for the use of "natural" on pet food labels are that the product should not contain any chemically synthesized ingredients.  Exceptions can be made when chemically synthesized vitamins or minerals are used as long as there is a disclaimer on the label (eg, "natural with added vitamins and minerals.").  Other descriptors, such as "organic," "holistic," "gourmet," and "human grade" have no legal definition for pet foods and are purely marketing terms.

Seniors

It has often been said that aging, in itself, is not a disease.  However, aging is often associated with a variety of diseases.  Nutrition can be a powerful tool in maintaining health, preventing disease, and in helping to manage disease.  However, deciding on the "best" diet for an older dog or cat can be a difficult decision; there is no one best diet for every older animal.  Animals are individuals so just because a pet turns 7 or 10 or even 13 years old doesn't necessarily mean it's old.  The aging process depends on a variety of factors including breed, genetics, and health problems.  Therefore, just because a food is marketed for older animal, doesn't mean it's right for every older dog or cat.

Individual differences aside, there are a number of changes that occur with aging that can affect nutritional requirements.  Unfortunately, little research on companion animal aging and nutritional requirements has been done so much of our assumptions are based on research in other species.  In other species, digestion and absorption of nutrients can be impaired with aging.  Dogs tend to have decreased energy requirements, decreased activity, and to gain fat and lose muscle.  Immune function and kidney function also decline with age, although the degree to which this occurs depends upon the individual animal.  While these structural or functional changes are thought to occur in older dogs and cats, minimal research has been done on changes in nutritional requirements that can result. 

In people, there has been a great deal of work on specific requirements for the elderly and these can be very different from younger adults.  In the new dietary reference intakes (DRIs) for people, people are now separated into additional age groups: 19-30 years, 31-50 years, 51-70 years, and >70 years for men and women. When enough information is available, recommendations are made for each age group.  If there are not enough data to distinguish differences in requirements between these age groups, information is given for a larger, combined age group.   Therefore, the direction is to have established requirements for each age group, including people >70 years.  Currently, in cats and dogs, adults are considered as a single group, whether the animal is 2 years old, 8 years old, or 15 years old.  More specific requirements for elderly animals would be beneficial as the requirements of older dogs and cats are most certainly different from a young adult.

Even if requirements are altered in older dogs and cats, adjustment of the diet may or may not be necessary or even desirable in the average older animal. Many older dogs and cats do very well by continuing to eat a good quality commercial diet designed for adults.  Others, however, will benefit from changing to a "senior" diet.  It is important to understand that there is no legal definition for "senior" or "geriatric" foods.  Although the title generally implies lower protein, lower phosphorus, and a lower caloric content, the levels vary with each company and each company's senior food will have different properties.  Therefore, some foods will meet the needs of an individual animal better than others.

"Senior" foods vary depending upon the manufacturer, but there are a number of nutritional adjustments that are common to many:

1.        Reduced protein.  Although there is a common belief that protein restriction is helpful for older animal, there is little scientific evidence to show that low protein foods are beneficial for the healthy older dog or cat or that moderately high protein foods contribute to the development of kidney disease.  Therefore, dogs and cats should not be fed a low protein diet just because they are old (if moderate to severe renal disease is present, then some protein restriction may be beneficial).  In fact, foods highly restricted in protein may actually be too low in protein for many older animals and can contribute to muscle loss.  The "optimal" protein level for older dogs and cats, however, is still controversial.  Some companies manufacture "senior" diets with low protein, some have moderate protein, and some nutritionists actually recommend that older dogs and cats eat a higher protein level than younger animals.  The jury is still out but for older animals without significant renal or hepatic disease, it is wise to avoid reduced protein diets. 

2.        Phosphorus.  Phosphorus can contribute to the progression of renal disease, so phosphorus restriction is recommended for animals with significant renal disease.  It is not known, however, whether high dietary phosphorus directly contributes to the development of renal disease.  Nonetheless, high phosphorus foods may not be ideal for older dogs and cats.

3.        Sodium.  Sodium levels are often reduced in "senior" foods.  Sodium restriction is unnecessary for the general population of older dogs and cats, but may be recommended if cardiac disease is present.  Even with early cardiac disease, severe sodium restriction is not necessary and avoiding high sodium intake should be the goal. In more advanced congestive heart failure, more additional restriction of sodium may be beneficial.

4.        Calorie adjustment.  Many dogs and cats (and people) tend to gain weight as they age.  In these obesity-prone animals, decreasing the number of calories eaten (either by feeding less or changing to a food with a lower caloric density) will help to prevent weight gain.  Those extra pounds around the middle are not innocuous and can cause or exacerbate other diseases.  On the other hand, not all animals gain weight as they age.  If a patient is one that is gradually losing weight or muscle with aging and there is no underlying medical condition, a more calorically dense (and possibly also with some adjustments in other nutrient levels) should be selected to help to prevent weight loss. 

5.        Fiber.  Increased soluble or insoluble fiber intake may be useful for dogs and cats that have decreased intestinal motility and are prone to constipation, but high fiber foods may not appropriate for animals with trouble maintaining weight since high fiber foods are generally low in calories.

6.        Supplemental vitamins and minerals.  If a good quality commercial food that has undergone AAFCO feeding trials is being fed, supplementation is unnecessary.  Some nutritional supplements may be helpful in certain diseases, and future research will help to better define where they can be beneficial and where they can cause problems.

There is an increasing interest in geriatrics among the pet food companies.  A new niche has developed for special diets for geriatric companion animals so more and better research into their unique requirements will be done.   Hopefully, this will provide the necessary information to develop separate nutritional profiles for elderly dogs and cats.  Unfortunately, pet food manufacturers will never be able to design a single food that meets the needs of every older animal.  Therefore, it is important to evaluate the individual patient's condition and health status to determine an appropriate food that will maintain a proper body weight and provide optimal nutrient levels.

In selecting the optimal diet for an older animal, the first thing to consider is overall health.  If the animal is healthy, in good body condition, and eating a good quality adult food, there is no reason to change foods. If the patient has one of the diseases often seen with aging such as arthritis, diabetes, cancer, dental problems, cardiac disease, or renal failure, dietary adjustments may help improve clinical signs or even slow progression of the disease.  For cats with diabetes mellitus, for example, dietary modifications such as increasing fiber or using a high protein, low carbohydrate food may help to control the disease and reduce insulin requirements. Reduced sodium foods may be useful in dogs with advanced congestive heart failure and can help reduce the diuretic dose required. 

The best diet (or diets) should be based on the individual animal's clinical signs, laboratory results, and stage of disease.  As the disease progresses and medication adjustments are required, further dietary changes also may be necessary.  Dietary modification can help to optimize health in the healthy dog and cat and to modulate disease as animals age.  The large variety of commercial diets and their variable nutrient contents provides many choices for optimizing the health of the elderly patient.

Recommended reading

Baldwin K, Bartges J, Buffington T, Freeman LM, Grabow M, Legred M, Ostwald D, Jr. AAHA nutritional assessment guidelines for dogs and cats. J Am Anim Hosp Assoc 2010 46: 285-296

Hutchinson D, Freeman LM, Schreiner KE, Terkla DG.  Survey of opinions about nutritional requirements of senior dogs and analysis of nutrient profiles of commercially available diets for senior dogs.  Intl J Vet Res Vet Med 2011; 9: 68-79

WSAVA Nutritional Assessment Guidelines Taskforce:  Freeman L, Becvarova I, Cave N, MacKay C, Nguyen P, Rama B, Takashima G, Tiffin R, Van Beukelen P, Yathiraj S.  2011 Nutritional Assessment Guidelines.  J Small Anim Pract 2011; 52: 516-525.

Hutchinson D, Freeman LM. Optimal nutrition for senior cats.  Comp Cont Ed Small Anim Pract (In Press)