Royal Canin Nutritional Information

6. Royal Canin Nutritional Information

Focus on: Phosphorus

Etymologically speaking, the word phosphorus means ‘light-bringing.’ It was discovered in 1669 by a German alchemist, Hennig Brandt. By evaporating urine and calcifying the residue, he obtained phosphorus in gas form that shone in the dark.

In the form of phosphates, phosphorus enters into the composition of bone. Eighty-six percent of the phosphorus in the organism is stored in the structure of the skeleton.

Phosphorus is also incorporated into large molecules such as DNA, RNA and membrane phospholipids. In addition, it is an active constituent of the adenosine triphosphate molecule (ATP), which stores the energy living organisms need to function properly.

Following the reduction of the glomerular filtration rate (GFR), phosphorus accumulates in the organism that responds by increasing the secretion of parathyroid hormone (PTH). This response initially helps maintain the phosphorus within normal thresholds, but also leads to the release of phosphate and calcium from bone reserves.

In time, even this compensatory response is not enough to restore homeostasis. Phosphorus and calcium accumulate, leading to the mineralization of soft tissue (kidney, heart). In the kidney, this phenomenon accelerates the loss of functional nephrons.

While it is vital to limit the phosphorus content in the food, the difficulty lies in the necessity of finding raw ingredients that are low in phosphorus. Animal protein sources traditionally used in dog food are fairly high in phosphorus. For example, there is 1.6-2.5% phosphorus on a a dry matter basis in dehydrated poultry proteins. This level is dependent on the overall content of remaining mineral matter after sieving. Vegetable protein sources that are lower in phosphate concentration (wheat or corn gluten, soy protein isolate hydrolysate) are an interesting alternative.

Figure 28. Phosphorus content of several protein sources used in dog food (Royal Canin internal data).

Key points: Treatment and Prevention of Chronic Kidney Disease in Cats

Diet composition plays an important role in maintaining homeostasis in cats suffering from chronic kidney disease (CKD). The recommendations with respect to nutritional treatment must be tailored to the patient, based on the clinical and laboratory results. CKD is a progressive disease and so examinations must be conducted regularly if treatment is to be efficient.

The priority dietary modifications have the following objectives:
- combating against anorexia and maintaining sufficient energy consumption
- preventing secondary renal hyperparathyroidism by controlling hyperphosphatemia
- limiting azotemia and/or uremia
- preventing hypokalemia
- combating the risk of metabolic acidosis
- strengthening the antioxidant defenses

Combating Anorexia and Maintaining Sufficient Energy Consumption

The palatability of the food is a key factor in stimulating food consumption in cats with CKD and promoting observance of the nutritional treatment.

A high-energy food permits the volume of the meal to be reduced, which facilitates the feeding of animals whose appetites are affected by the disease.

Preventing Secondary Renal Hyperparathyroidism by Controlling Hyperphosphatemia

The aim is to limit the phosphorus level of foods to 0.7 - 1.0 g/1000 kcal (around 0.3 - 0.4% of a dry food of 4000 kcal/kg). This restriction helps double the life expectancy of cats with renal insufficiency (Ross et al., 2005). If such a low level does not stabilize the phosphatemia at the desired level (Figure 29), the use of phosphorus binders must be considered.

Figure 29. Therapy based on the plasma phosphate concentration measurement. From F. Hebert, 2008.

Limiting Azotemia and/or Uremia

When CKD leads to uremia, it is recommended to reduce the protein intake to prevent the uremia altering the cat’s well being to too great a degree. Measurement of the protein/creatinine ratio in the urine is helpful to appreciate the response to protein restriction (reduced production of nitrogenous waste).

It is also important to provide the cat suffering from renal insufficiency with long-chain omega-3 polyunsaturated fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]). In dogs with CKD, the administration of a diet with a high-fish oil content slows down the deterioration of GFR (Brown et al., 2000).

Preventing Metabolic Acidosis and Hypokalemia

Metabolic acidosis requires oral alkaline treatment. Metabolic acidosis increases the risk of hypokalemia: potassium gluconate or potassium citrate treatment is therefore indicated.

Preventing metabolic acidosis and hypokalemia in cats with CKD entails avoiding acidifying foods and make sure the potassium intake exceeds the requirement. The systematic prescription of potassium supplements will generally be redundant if a food tailored to the needs of the kidneys is used.

Strengthening the Antioxidant Defenses

Enriching the levels of vitamin E, vitamin C, taurine, lutein, lycopene, betacarotene, etc. in the food helps limit the oxidative stress that aggravates CKD lesions.

The nutritional diet is the cornerstone in the treatment of renal insufficiency. In cats, it has been proven to contribute to a significant increase in life expectancy by slowing down the progression of the kidney disease.