For several decades now, low protein diets have been recommended for older dogs. While based on the flimsiest scientific evidence (the original research was done on rats, not dogs), the recommendation quickly became commonly accepted. The pet food industry welcomes all information that allows them to peddle high carbohydrate grain-based foods for premium prices, and the supposed findings seemed to make sense to many people. After all, don't high protein diets tax the kidneys, and don't older dogs often have diminished kidney function?
The Low Protein Myth
In recent years, a number of well-designed studies have proven unequivocally that dietary protein levels have no effect on the development of kidney disease in dogs. Moreover, when dogs with severely compromised kidney function were divided into two groups and put on diets providing 18% protein and 34% protein respectively, the 34% group fared significantly better. Other studies have demonstrated that protein levels as high as 44% have no adverse effects on kidney function in dogs with kidney disease.
Low protein, high carbohydrate diets, on the other hand, have been associated with increased risks of diabetes and urinary tract problems, diminished kidney and liver function, lower lean muscle mass and higher body fat levels (which, in turn, predispose seniors to other ailments from arthritis to heart disease). Sadly, the vast majority of commercial senior diets still fall into the low protein/high carb category. To make matters worse, a significant percentage of the already low protein levels in these foods is supplied by grains and vegetables.
Researchers have also discovered that seniors, much like puppies, do not metabolize proteins as efficiently as younger adults. This means that your pit bull senior citizen not only requires more protein (40% or higher is ideal), but better quality protein. Protein digestibility of dog food ingredients varies greatly from near 100% to less than 50%. High quality protein sources include eggs, muscle meats, and some organs like liver, kidney, and heart, while low quality proteins derive from plant sources such as corn and wheat as well as inferior animal sources like meat & bone meal and by-product meals.
Do Older Dogs Need Less Fat and Calories?
Another standard recommendation for senior diets is that they should contain reduced fat levels and calories. This dietary guideline is based on the belief that older dogs have less lean muscle mass and are less active. Sometimes that is indeed the case. However, we also know 11 and 12 year old pit bulls who are lean, athletic, and highly active. These "senior citizens" have greater energy requirements than many 3 year-olds, and they thrive on high fat raw diets.
Less active dogs of all ages can benefit from a diet that's lower in fat and calories, but we shouldn't assume that older dogs will automatically fall into this category. If your canine senior citizen is lean and active, there's no reason not to pick a high protein food that's also high in fat (20% or more). Otherwise, stick to a high protein food that limits fat content to 12-16%. Orijen Senior and EVO Weight Management are two kibbles that provide high levels of quality proteins (40% and 52% respectively) and a moderate amount of fat (15%).
If your older pit bull needs to lose weight, you may opt for slightly lower fat levels, but diets providing less than 9-10% fat tend to be counterproductive. Not only does palatability drop significantly with super low fat foods, but your dog will be left feeling hungry and deprived. As a result, he'll be more inclined to raid the garbage or "supplement" his meals in other ways. The only time a super low fat diet may be indicated is if your pit bull has health problems that interfere with lipid metabolism. However, even dogs with chronic pancreatitis or EPI usually do not require a diet that supplies less than 9-10% fat.
What about Fiber?
Since older dogs are more prone to constipation, small amounts of fiber in your senior's food can be beneficial. Unfortunately some commercial foods formulated for seniors and overweight dogs contain high levels of low quality fiber (peanut hulls, cellulose, rice hulls, etc.) based on the erroneous belief that these indigestible fillers will enable dogs to "feel full" and be satisfied with lower calorie fare. Research has shown that this is not the case. Not only do high fiber levels (8-10%, prescription diets can be even higher) not promote weight loss in dogs, but they can actually interfere with nutrient absorption.
Antioxidants and Nutraceuticals
A well formulated senior diet would contain increased amounts of antioxidants and omega-3 fatty acids (preferably from fish rather than plant sources), as well as glucosamine and chondroitin for the prevention of joint problems. Probiotics and digestive enzymes can also be helpful for older dogs who do not absorb nutrients as efficiently as their younger counterparts. Keep in mind, though, that you can always add these supplements yourself.
When Is Your Pit Bull a Senior?
Traditionally, dogs have been considered seniors when they enter the final third of their life. American Pit Bull Terriers have an average life expectancy of 12-14 years. Consequently an 8-9 year old pit bull would be a senior. However, with the right nutrition and supplements, limited drugs and vaccinations, and plenty of exercise, an 8-9 year old won't even be close to starting to slow down!