The prevalence of chronic kidney disease in the cat is seemingly on the up. Generally, what goes up, must come down, but when we look at the factors underlying kidney disease, there is a real concern that this may not happen. Currently, it is suggested that 1 in 3 cats suffer with some form of kidney disease. So, what can we do about it? Let’s take a look at kidney disease in a little more detail, why the kidneys are so important and some of the underlying factors that contribute to the development of it. What is kidney Disease Chronic kidney disease in cats is a prolonged process marked by the irreversible loss of kidney function. It is suggested that the early stages of CKD are often missed in cats, likely because many are outdoor cats so urination and drinking behaviours may not be as easily noted, along with vomiting etc. Kidney disease is generally associated with ageing pets; like all things, kidneys too get tired as they get older. But there are new concerns, well, new in 2014, that younger cats are seemingly presenting with the disease too. Where 30-50% of cats 15 years of age or older suffer with CKD, 13% of those under the age of 4 also suffer. Symptoms of Kidney Disease in the Cat: Increased thirst Increased urination Reduced appetite Weight loss Vomiting Fatigue Weakness Bad breath There are 4 stages of kidney disease in the cat, they are based on serum creatinine concentration: stage 1 through 4, with 2 being mild, 3 being moderate and 4 being severe. Findings here Why are the kidneys so important? The two bean shaped organs have vital functions in the body. They monitor fluid levels in the body, control and process waste and release vitamins, minerals and hormones. Their main function is to collect waste products and turn them into urine. Blood enters the kidney though arteries and splits into nephrons. The nephron splits into two nifty mechanisms to filter the blood. This includes the glomerulus and tubule. The glomerulus is like a sieve, allowing certain compounds from the blood into the tubule. The tubule then senses whether any of these compounds are needed around the body. If so, they are absorbed into the body. The tubule also senses waste products, like urea which is produced during the break down of protein. It redirects urea as urine which travels down the ureter, into the bladder to be excreted. The kidneys also activate vitamin D, and release hormones such as erythropoietin which is needed to produce red blood cells and renin which regulates blood pressure. Without the kidneys, the body would be full of blood that hadn’t been sieved and full of harmful waste. It also wouldn’t be receiving the vitamins and minerals, which, without being dramatic, are in fact critical to life. Causes of Kidney Disease There are genetic predispositions to developing kidney disease; certain breeds that are more likely to suffer with kidney issues include the Persian, Siamese, Ragdoll, Russian Blue and MaineCoon. But other than acute renal failure caused by poisoning (plants, pesticides etc), there are other factors that can contribute to kidney issues. As we have established, one of the kidney’s main role is to filter helpful and harmful compounds in the blood. It stands to reason that the more harmful compounds it must process, the sooner it reaches its retirement party! It is often suggested that chemical exposure isa progression factor in the disease and sadly cats are regularly exposed to cleaning agents, pesticides, and many more environmental toxins. These can be ingested, inhaled, or exposed transdermally (through the skin). The foods fed to cats can also impair kidney function. Mycotoxins are a diverse group of chemicals produced by a diverse group of fungi. However, mycotoxins, can be nephrotoxic (toxic to the kidneys). Studies have demonstrated that anywhere between 62% to 100% of cat foods sampled had mycotoxin contamination. Findings here There are also reports of melamine toxicity in cats, resulting in kidney damage. You guessed it; the source of melamine was contaminated food. Findings here Mild dehydration is also a risk factor for kidney disease. This is a concern because of the moisture content in many commercial foods. Dry-based cereal foods rank low on moisture,with dogs demonstrating increased drinking to counterbalance their water requirement. Cats, however, have an evolutionary low thirst-drive. Cats are obligative carnivores, meaning they get what they need from animal tissue. Therefore, they would naturally get moisture from their whole prey kills. But they are no longer getting the same level of moisture with a dry based diet and their thirst-drive hasn’t yet caught up (in evolutionary terms)! Starch also poses a risk for developing periodontal disease. Wait, what has periodontal disease got to do with the kidneys? And what has starch got to do with cats? Stick with us. Starch is the storage form of energy in plants; and then becomes a source of sugar in an animal’s diet. Bacteria found in the mouth feed off these starches and form a biofilm called plaque. This slowly degrades the tooth and surrounding structures. Not only that but the frequency of eating can contribute to the development of periodontal disease. Saliva can perform a clean-up between meals, but this becomes less of an option for the cat who is free fed throughout the day. The long and the short of it, many dry-based foods contain starch, which is a risk for periodontal disease. Periodontal disease is regularly implicated as a risk factor for kidney disease due to the relocation of oral bacteria throughout the body. Despite this, there are also things that can help mitigate the risks associated with kidney disease. Water intake is of utmost importance in all kidney patients. Therefore, a high moisture diet is essential. When offering drinking water, ensure it is filtered to remove any potential harmful compounds before they even get into the body. Protein restriction in kidney cases is much discussed and often controversial. Surely
Cats are obligate carnivores. What this essentially means is that cats rely on nutrients in animal tissues to meet their specific requirements. Not plants…. but animal tissues. So, let’s explore the world of the cat in a little more detail and see how we can support their nutritional needs to not only survive, but thrive. Evolutionary events have led to a unique digestive and metabolic peculiarity. Whilst in many other species, we have the three macronutrients, fat, protein and carbohydrates, cats seem to have no physiological requirements for carbohydrates. Now where this becomes interesting is that the brain and red blood cells have an absolute need for glucose, and we know that carbs equal glucose, so where do cats get glucose from? Surely without carbohydrates they would be forever hypoglycaemic? Well, through a process of gluconeogenesis, they produce glucose. Us humans, and dogs too can perform this process, but cats have it down to a fine art. Gluconeogenesis is the metabolic process by which glucose is produced from non-carbohydrate precursors, like lactate and amino acids (and we know that amino acids are the building blocks of protein). All amino acids, except leucine and lysine are gluconeogenic and alanine is the major gluconeogenic amino acid. The process mainly occurs in the liver, but some processes are carried out in the kidneys and a small portion is carried out in the intestines. It is thought that cats evolved with the process because of their proportionally large brain. As we have mentioned, the brain has an absolute need for glucose, and it is thought that the brain demand for glucose in cats is around 30% whereas for us humans who have a much larger brain is 44%. Cats wouldn’t have been able to consume high enough levels of carbohydrates from their natural prey diet, so their body had to adapt to survive. This evolution has resulted in a small capacity for starch digestion, having limited salivary amylase which is similar to dogs. Amylase is found in the feline pancreas and chyme, but the activity is incredibly low compared to other animals. Their pancreatic maltase activity is also extremely low. Cats seem to know this and when given the opportunity will choose low carbohydrate but high protein diets in order to balance their own macronutrients. They also don’t appear to have developed a sweet tooth. In evolutionary terms, us humans would have stocked up on sweet-tasting foods, but cats didn’t need to. To that end, they don’t show any preference for natural sugars or artificial sweeteners. In the absence of protein, cats will opt for fat. When fat and protein is limited, but carbohydrate is unlimited, cats appear to experience nutritional deficits. This is largely due to their requirement for taurine. Taurine is present in a range of meats and seafoods but is essentially absent from plant material. This is another reason why cats are deemed obligate carnivores. Dietary deficiency of taurine is linked with a range of important conditions. Retinal Degeneration More commonly known as retinal atrophy, it is the complete or partial wasting of the retina. The cells degenerate over time, eventually leading to blindness in the cat. First signs include the eye being more reflective and the pupils are more dilated than normal. Lesions are usually bilaterally symmetrical. A dietary deficiency must be present for several months before changes appear but lesions are progressive whilst the cat is on a deficient diet, although visual defects don’t tend to appear until the late stages of degeneration. Reproduction Taurine deficiency is well known for having marked effects on reproductive performance and on the growth and survival of the young. Cerebellar dysfunction often occurs in kittens of taurine deficient mothers. Dilated Cardiomyopathy Taurine deficiency can lead to weakening of the muscle cells in the heart, causing a condition called dilated cardiomyopathy (DCM). Taurine is essential in membrane stabilisation. Many cases of feline dilated cardiomyopathy are associated with low plasma taurine levels and when administered with taurine, they show an improvement. Sadly, when left untreated for too long, dilated cardiomyopathy will progress to heart failure and death. The importance of taurine in commercial cat food was noted in the late 1980’s; following reformulation of cat foods, cases of taurine related dilated cardiomyopathy decreased from 28% to just 6%. Findings here Including taurine, eleven amino acids are recognised as essential for the cat, but some have a higher utilisation than others. Taurine is necessary for vision and the function of the cardiac muscle, nervous system, immune system, and reproductive systems. Arginine is used in the urea cycle and methionine and cysteine are incorporated into antioxidants, hair and urinary outputs but are primarily gluconeogenic amino acids, catabolised to provide energy. With their incredible utilisation of amino acids, cats present what is known as a carnivore connection. This is a bundle of carbohydrate-sensitive conditions, first noted in humans who were late to join the carbohydrate-eating party (Paleo-Indians, Australian Aborigines for example). In short, there is a higher incidence of conditions like glucose intolerance, insulin resistance and diabetes. However, other data has suggested that carbohydrate content is of little effect, and these conditions are instead associated with overweight or obese cats. 44% of cats in the UK are deemed as overweight or obese by veterinary professionals. Whereas when surveyed, only 8% of owners think their cat needs to lose any weight. Obesity is defined as abnormal or excessive fat accumulation that presents a risk to health. This is a result of excess calories that the body cannot use; these calories can be from any of the macronutrients. It is often considered that a major factor driving obesity is the practice of free-feeding, in which a bowl of dry food is available for consumption by a cat throughout the day, and simply topped up as it runs out. There is also recent research that suggests feeding cats just once a day may control hunger better than several feeds a day. Findings here This study demonstrated that the cats showed a faster
