Approximately one-third of cats are considered senior or mature,1 with many geriatric cats living longer lives due to improvements in veterinary care. While recent years have seen the development of various guidelines regarding medicalization and therapeutic management for senior cats, nutrition for these animals is still not well defined. Further, many diets targeting senior cats do not contain significant differences in nutrients when compared to diets formulated for adult cats.2
The process of aging varies greatly from patient to patient. While certain physiological and anatomical changes are often associated with progression of age, the timeline in which these changes occur is not consistent. Most commonly, aging cats experience alterations to cognition, weight loss or gain, and changes in muscle condition, as well as a decline in hearing, sight, and sense of smell. These pets may also have decreased skin elasticity and slower wound healing. Finally, there may also be differences in how nutrients are digested and absorbed.
Age-related medical diseases and dysfunctions are common in older cats, with chronic renal disease, cardiac dysfunctions, dental disease, osteoarthritis, and neoplasia all notably reported. A study investigating renal disease in felines reveals prevalence and severity of this condition increases with age, with incidence in cats aged 15 to 20 years double what is observed in younger age ranges. Further, the occurrence of IRIS Stage 3 renal disease is limited to cats older than 10 years.3
These factors highlight the importance of individualized nutrition for senior cats. Underlying health conditions and comorbidities drastically affect the nutritional needs of cats, but even in healthy seniors, nutritional priorities should be identified using information obtained from a thorough history, physical examination, and diagnostic testing. Patient predispositions and lifestyle should also be considered, as well as current feeding management.
A nutritional assessment should be done at every appointment, regardless of age; however, given the increased risk of developing health conditions, these assessments are particularly important for senior cats. A nutritional recommendation should include specific details on diet and feeding amounts, as well as suggestions about how to feed.
BCS and caloric density
Unexplained weight loss is a common concern in older cats. While maintenance energy requirements (MER) for dogs appear to decrease with age, in cats, studies show a decrease until 11 years of age, at which time these requirements increase.4
These changes may stem from a reduced ability to digest fat. Indeed, it has been shown this occurs in 10 to 15 per cent of cats aged seven to 12 years, and 33 per cent of cats older than 12 years.5 As such, some guidelines regarding nutritional needs for senior cats suggest increasing caloric intake by up to 25 per cent.6 While having a body condition score (BCS) below ideal has been negatively associated with survival and lifespan,7 we must remember any changes in fat digestion are both gradual and variable between patients.
On the other hand, obesity rates in cats continue to climb, with a 2017 U.S. Banfield Pet Hospital report detailing a 169 per cent increase in obese cats over 10 years.8 Feline patients should be re-evaluated regularly to assess weight and BCS and have their energy intake adjusted as needed to maintain an ideal score.
Obese and overweight cats will benefit from a veterinary-guided weight-loss plan. Obesity can exacerbate comorbidities common in older cats, such as diabetes mellitus and feline lower urinary tract disease. Achieving a healthy body weight can be considered a crucial step in the management of these and other co-morbid health conditions.
Obesity has also been linked to osteoarthritis. Forty-one per cent of cats with osteoarthritis are also overweight or obese,9 which makes sense given the strain that extra weight can place on joints, as well as the reduced mobility patients with osteoarthritis experience. Weight loss—even as little as six per cent—has been shown to be beneficial in reducing lameness in arthritic dogs,10 and similar benefits are also likely to be seen in cats. Weight loss should be prioritized for these patients even if ideal body weight cannot be achieved, as studies have shown even partial weight loss can dramatically increase quality of life.11
Meanwhile, cats that are underweight may benefit from a more energy-dense formula to help encourage weight gain and preservation of muscle mass. Before nutritional recommendations can be made, however, further exploration into the cause of weight loss is necessary. If the cat has poor appetite and is not consuming adequate calories to maintain their weight, it may be necessary to rule out causes of dysphagia or nausea. If the cat has a good appetite and is being fed appropriate calories to meet their nutritional needs, diagnostics should focus on identifying conditions causing poor digestion or increased energy loss.
Many diets marketed towards senior cats will have elevated levels of fibre—in fact, this was the only nutrient found to be significantly different when comparing diets marketed for adult cats versus senior cats.2 Fibre decreases caloric density and can improve satiety, which can be beneficial for cats who are prone to weight gain, but should not be a substitute for a weight-loss formula in overweight or obese cats. Further, these diets are not ideal for cats that are underweight (with or without a poor appetite), as this will increase the challenge in meeting their caloric needs. Veterinarians, therefore, should avoid generalized recommendations without considering individual needs. It is important to schedule follow up with regular weight checks to ensure caloric needs are being met and body condition is maintained.
Muscle condition and protein digestibility
In addition to body weight, it is common for senior cats to experience changes in muscle condition. Sarcopenia is the muscular atrophy that occurs as a result of aging and is a common cause of musculoskeletal weakness in older patients. Cats with certain medical conditions (i.e. chronic kidney disease, heart failure) can also experience a type of muscle loss called cachexia. Unfortunately, differentiating these two conditions can be challenging. Regular veterinary care and diagnostics play an important role in identifying underlying diseases that may be contributing to cachexia.
Muscle condition scoring is a valued tool for helping to detect muscle atrophy in senior cats. This scoring involves evaluating muscle mass over the spine, scapula, skull, and hips to identify when muscle loss is present. As with most things in veterinary medicine, having a baseline of normal conditioning for the patient can be useful to identify subtle changes. It is important to note, as well, obesity can mask muscle loss, making changes in muscle conditioning and overall weight less obvious. Associated decreased mobility and lack of exercise can further exacerbate muscle atrophy. (An excellent muscle condition score chart for both cats and dogs can be found in the World Small Animal Veterinary Association [WSAVA] Nutrition Toolkit at wsava.org.)
Like with fat, a reduction in protein digestibility is also seen in senior cats, presenting in approximately 20 per cent of felines over the age of 14 years.5 As such, cats in this age group may benefit from nutrition with higher levels of protein to assist in maintaining lean muscle mass. However, quality can be just as important as quantity, and specific amino acids play a role in maintaining lean muscle mass. For example, L-carnitine mobilizes fatty acids into the mitochondria to be used for energy, thereby targeting fat as an energy source over muscle. Proteins should always be selected for their digestibility and amino acid profile to ensure optimal utilization by the body.
Lower levels of protein are a common component of renal formulas. There is sometimes a tendency to transition cats to these diets as a precautionary measure in their senior years, especially in situations where regular screening diagnostics are not being performed. It is, however, important to avoid protein restriction in cats that do not require it, as this could compound any decrease in protein digestibility and exacerbate the risk of muscle atrophy. Instead, formulas moderately restricted in protein and phosphorus are often utilized in early chronic kidney disease and are well tolerated in healthy older cats.12
How to feed
When making nutritional recommendations for senior cats, consideration for how the diet is fed is as important as the food itself and its portion.
Aging cats experience a decline in their special senses, including sight, hearing, and smell. The ‘smell’ factor is an important component of palatability for cats, as this sense is much stronger than a feline’s sense of taste, and they possess 12-times more olfactory receptors than humans.13
A recent study of aging cats showed canned foods served at warmer temperatures were preferentially selected.14 This has been anecdotally appreciated by animal professionals and owners alike, but the most preferred temperature has been identified at 37 C (which coincides with the body temperature of rodents, a natural food source of cats).
The same study also saw significant differences in the aromatic profile of canned foods at this temperature. Acids and sulphur-containing compounds (i.e. profiles associated with cheese and meat flavours) increased, while citrus and rancid profiles decreased. It is possible warmed foods had enhanced smell and, therefore, taste profile, which could be beneficial in senior cats as their sense of smell decreases.
Alterations in cognition can also be seen in senior cats. Behavioural changes associated with this include excessive vocalization, inappropriate urination, altered sleeping habits, and mood changes.15 In more advanced stages, to minimize potential interruptions in feeding, emphasis is typically placed on reducing environmental changes; however, proactively providing for senior cats’ environmental needs could offer added benefit.
Puzzle feeders, for example, are an excellent inclusion in the feeding strategy of cats of all life stages. These can be successfully introduced to senior cats, even in cases when the animal has not previously been exposed to them. These feeders provide mental and physical stimulation and help increase the feeding time budget to more closely resemble natural feeding behaviours of cats. They have been used alongside the provision for other environmental needs in the management of feline cognitive dysfunction and obesity.16
Both the personality and physical abilities of a specific senior cat should be taken into consideration when selecting puzzle feeders. For example, stationary feeders able to be adjusted to easier settings may be beneficial to cats with limited mobility. Additionally, introduction of the feeder should be done gradually, as this gives the cat time to work out the problem before regular access to food is removed. Some pets respond well to hiding kibble around the house to encourage foraging, but potential obstacles such as stairs or elevated climbing surfaces may need to be avoided.
Aging is an individual process, and nutritional considerations of senior cats must reflect this. Age-related factors associated with nutrition include differing energy requirements, variations in protein and fat digestibility, changes in weight and muscle conditioning, and decrease in sense of smell and cognitive abilities. Considering the incidence, time of onset, and rate of progression of these potential changes is variable among patients, nutritional recommendations should always be made based on the individual needs of the cat. Nutritional goals should focus on maintaining appropriate body and muscle conditioning, providing for environmental needs, and addressing any underlying health conditions or predispositions.
Vanessa Tonn, DVM, graduated from the Western College of Veterinary Medicine in 2012. She gained experience working across Canada in private and emergency practice, where she was fortunate enough to treat patients ranging from tree frogs to elephants and everything in between. Dr. Tonn joined Royal Canin as a scientific communications specialist in 2019. In this role, she is able to share her passion for nutrition with pet professionals and caregivers alike, with the ultimate goal of making a better world for pets.
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