Some cats -- such as those suffering from kidney disease -- need to follow a low phosphorus diet. If your vet recommends such a diet, there several food options that will ease the burden on your cat's kidneys and encourage renal health. Your cat should avoid other foods -- such as milk -- that are high in phosphorus. A cat owner should understand what a low phosphorus diet will do for the cat, how to choose the right foods and how to encourage the cat to eat them.
What it does
A low phosphorus diet is easy on the kidneys compared to other diets, making it a common, and sometimes necessary, choice for cats with kidney disease or chronic renal failure. The kidneys maintain healthy phosphorus levels, so when your cat's kidneys are not functioning efficiently, phosphorus levels will rise. A low phosphorus diet keeps these levels low without burdening your cat's kidneys with their previous workload.
What to feed your cat
If your cat is sick with kidney disease, your vet will prescribe a low phosphorus diet, but if you want to get a head start on your own, your local pet shop should sell several options. Look for veterinary formulas for kidney or renal function and formulas with reduced protein. Dr. Scott Brown at the University of Georgia recommends that cats with chronic renal failure have a phosphorus intake of 0.5 per cent by dry matter analysis.
Dry matter analysis
You may be tempted to compare phosphorus levels on cat food labels and buy the food with the lowest percentage you can find. While this is a good idea, labels can be misleading. Because every cat food has a unique amount of moisture, the percentage of other ingredients varies accordingly, and comparing dry food and canned food can be especially confusing.
For an accurate comparison, do a dry matter analysis--factoring out the food's water content. To do this, subtract the water percentage to find the dry matter percentage. Next, divide the per cent of phosphorus by the dry matter percentage to find the true amount of phosphorus in the food. For example, if a food is 80 per cent water or moisture and has a 0.25 per cent phosphorus content, divide 0.25 by 20 per cent (0.25/0.20) for a dry matter analysis phosphorus content of 1.25 per cent.
Starting the cat's new diet
When starting your cat's low phosphorus diet, you may find yourself unable to entice your cat to eat the new food. Cats with chronic renal failure might be less likely to eat, too, as they do not feel well. Your vet may prescribe an appetite stimulant, but other tricks may help your cat adjust to the new diet. The Chronic Renal Failure Information Centre website and Dr. Brown recommend gradually adding the new food to your cat's old food, warming the food, and adding water, tuna juice or a broth to give it more moisture and make it more appetizing.
Veterinarian Jean Hofve, formerly the editor of the Journal of the American Holistic Veterinary Medical Association, warns not to supplement your cat's low phosphorus diet with foods high in protein -- such as meat -- as this will cancel the positive effects of the low phosphorus diet. The Chronic Renal Failure Information Centre website warns never to add onions to your cat's diet. Onions can cause anaemia, which is especially dangerous for a cat with chronic renal failure. In her article "Managing phosphorus in your renal diet," Maria Karalis lists milk as a high phosphorus food, so it should be eliminated from the cat's diet. And if your cat is ill, Hofve says the most important thing is preventing starvation, so if the cat does not like the new food, feed her whatever she will eat to keep her at a healthy weight.