by Dr Annabel Robertson BVSc (Hons) MANZCVSc MBA
I certainly remember seeing many chronic kidney disease (CKD) patients with significant muscle wasting when I was in small animal practice. What causes this muscle loss and is a so-called “low” protein renal diet responsible? The short answer is no and that is why using the nomenclature ‘low’ protein vs ‘restricted’ or ‘controlled’ can be misleading as it implies the diet is deficient in protein. Both k/d™ canine and feline exceed the minimum recommendations for protein set by the National Research Council (NRC). Provided a pet’s physiological requirements for protein are met, simply increasing protein is not going to increase muscle mass. If a pet consumes more protein than he/she requires, the excess will be converted to glucose and, eventually, fat.
Before we explore muscle wasting further, it’s important to remember that by far the most important thing we can do for the management of kidney disease is to feed these pets a renal diet. The core nutrition in k/d™, including its controlled levels of high quality protein, phosphorus and sodium, has been shown to increase the length and quality of life in both cats and dogs with CKD.(1,2) Not only does the controlled protein in k/d™ minimise the accumulation of nitrogenous waste products in the blood, decreasing the workload on the compromised kidneys, but it also directly helps to reduce phosphorus levels. In CKD, a patient’s ability to excrete excess phosphorus from the blood is compromised, leading to renal secondary hyperparathyroidism, with resulting mineralisation and further damage to the kidneys.
So if it’s not the protein levels in renal diets that’s causing muscle wasting, what is?
Assuming our CKD patients are older, muscle loss could be occurring for two main reasons:
- Sarcopenia: Age related muscle loss. Unfortunately this is a normal consequence of ageing!
- Cachexia: Muscle loss due to disease, a common consequence of CKD. Cachexia is a complicated multifactorial syndrome involving oxidative stress, inflammation and reduced protein synthesis.(3) Cachexia is still not truly understood in pets or humans and is currently the focus of extensive research as it has been shown to be a significant contributor to increased mortality and morbidity in humans.
The earlier we can identify cachexia the better, as once muscle is lost, it’s gone forever. The only way of assessing muscle condition accurately and documenting early muscle wasting is by performing a muscle condition score (MCS) at each exam. Guidelines on how to do a MCS are available from the World Small Animal Veterinary Association (WSAVA).
A renal food can only support muscle synthesis up to the level of its most limiting essential amino acid, and that’s why we are so excited to launch our upgraded Hill’s™ Prescription Diet™ k/d™ Canine and Feline diets in Canada.
The newly upgraded k/d™ has cachexia benefits as a result of its enhanced amino acid profile, added L-carnitine and omega-3 fatty acids from fish oil, as well as excellent palatability. These improvements to k/d™ help to support a pet’s natural ability to build lean muscle by providing the building blocks for normal daily protein turnover. By supplying greater than 130% of dogs’ and 150% of cats’ minimum essential amino acid requirements^, k/d™ helps ensure that even pets with advanced CKD and decreased appetite can meet the amino acid requirements necessary to prevent protein catabolism.
Finally, k/d™ canine now also contains E.A.T.™ (enhanced appetite trigger) technology. This technology was added to the k/d™ feline two years ago and significantly increased the palatability and caloric intake of the new formula compared to the original. We are now excited to include this technology in our canine product to increase palatability and caloric intake and help these dogs meet their daily energy requirements.
To learn more about muscle wasting and the latest on kidney disease management in dogs and cats, check out the link below to the Hill’s Global Symposium. This site features more than 20 free lecture recordings.