Chronic kidney disease (CKD) is one of the most common pathologies in elderly cats, with more than 30% of individuals over 15 years of age affected [1]. This condition is often accompanied by eating disorders, and yet maintenance of bodyweight in cats with CKD is positively correlated with their lifespan [2]. The palatability of renal diets is therefore a key element in the nutritional management of this disease.

Palatability 

Palatability is a complex, multifactorial phenomenon which encompasses not only the characteristics of the diet (odor, taste, texture, nutritional composition, etc.) (Table 1), but also those of the animal and its environment (perception of the food, experience, etc.). Indeed, dietary preferences vary enormously from one individual to another [3][4].

Some preferences are innate and may be linked to breed, anatomy [5], or individual genetics. Others are acquired over the animal’s life – for example, perinatal experiences have a major impact on future dietary choices [6] (Figure 1). Furthermore, different cats may react differently when presented with a foodstuff depending on previous experiences. These reactions can include a neophilic or neophobic response (i.e., attraction to, or repulsion by, novel diets), an anti-apostatic response (preferring foods that are not novel but are rarely offered) [7], apathy, or aversion. It is therefore essential to take the animal and its individual preferences into account when optimizing the palatability of a product. This is particularly important for cats with CKD.

The cat with CKD

Cats with CKD often exhibit dysorexia: 40% suffer from hyporexia, and 15% from complete anorexia [8]. Importantly, cats are genetically predisposed to correlate gastrointestinal discomfort after a meal with the food ingested immediately prior to this event, and they are more likely to refuse to eat that particular food in future [9]; both the taste and the odor of the product may be recognized and associated with the discomfort. The learning process is both quick and persistent, such that a single ingestion of a particular food can lead to lasting refusal. The nausea and vomiting experienced by CKD cats may therefore engender this type of reaction, so it is important to be able to offer an alternative food which both preserves the required nutritional strategy to manage CKD and offers a new sensory profile (odor, taste, texture) that differs from the previous diet, and that the animal finds appealing.

The nutritional constraints (low phosphorous levels and protein restriction) necessary for renal diets have a major impact on their palatability. However, these constraints are essential for good nutritional management of CKD, and dietary experts must therefore rely on their knowledge of the above parameters to make the food attractive and offer alternative solutions to the problem of aversion or reduced consumption.

With this knowledge, Royal Canin has recently developed a range of new renal diet products. These have been formulated using products that are perceived to be different by the cat, so if there is food aversion or decreased intake with one particular diet, it is possible to offer another product from the range to improve consumption. A clinical trial on 18 cats with CKD demonstrated that this organoleptic approach made it possible to offer an effective solution to appetite problems and to satisfy individual dietary preferences whilst supplying the required nutritional support [10](Figure 2).