They cannot convert beta-carotene to vitamin A. Cats must eat meat to survive. The principal function of carbohydrates in the process of manufacturing dry pet foods is to provide structural integrity to kibble. The starch works like a «cement» that holds kibble together, preventing crumbling throughout the manufacturing process. It is unusual for a dry pet food to be formulated with less than 40 percent carbohydrate ingredients because of the minimum requirement for extrusion. Starch works like a «cement» to hold kibble together!
Does that make you wonder what the long-term effect of cement is on your cat’s digestive system? Small Animal Clinical Nutrition, 4th ed. Hill’s Science Diet to do a lot of my research. This book, used by many veterinarian schools as a part of their nutrition curriculum, is a very large book packed with information on small animal nutrition. In the chapter on feeding normal cats, the author states, cats have evolved to a carnivorous diet that is high in protein and low in carbohydrates. Because they evolved as obligate carnivores, cats have difficulty digesting carbohydrates. In omnivores, both hexokinase and glucokinase is responsible for processing of carbohydrates into glucose.
The feline liver exhibits normal hexokinase activity but glucokinase activity is virtually absent. Protein metabolism is unique in cats with their unusually high maintenance requirement for protein. Unlike omnivores, cats cannot decrease liver enzyme activity when fed a low protein diet. It is not unnatural or unusual for a cat in the wild to fast. Even though they are successful hunters, they are not perfect and may go days without food. My own cats will sometimes go off their food for a day or more.
A potential cause of fatty liver disease in cats is protein deficiency. While the label on dry cat food will show what looks like sufficient protein, a good amount of that protein is coming from grains. I do not believe grains are a high quality source of protein for carnivores or that they are as able to utilize protein from non-meat sources. Cats fed a raw meat diet should not be prone to fatty liver disease, therefore, although I am concerned when one of my cats goes off his food, I do not expect to ever have to deal with fatty liver disease in any of my cats. There are many factors attributable to onset of fatty liver disease. Carnitine is an amino-group containing, vitamin-like substance found in high concentrations in mammalian heart and skeletal muscle. This amino acid is not considered to be essential by the AAFCO.
Methionine is added to most dry cat food brands and lysine is added to the higher end brands. As with most nutrients found in raw meat, I believe it is best to feed the real thing rather than supplementing with synthetic nutrients. In humans, a carnitine deficiency causes hepatic lipid accumulation and liver dysfunction. A similar connection is being investigated in cats. Also, carnitine increases lean muscle mass and enhances weight loss in obese cats. Many cats with idiopathic fatty liver disease are obese and often the disease is discovered after a fast, be it due to a stressful event, illness or even abandonment.
Perhaps these dry-food-fed cats are just barely getting by with the amount and quality of protein available in dry food. It is not uncommon for a cat fed dry food to become obese. A fast simply tips their digestive process over the edge. Very little is known about the causes of feline fatty liver disease. Except for Wiley, now deceased, none of the cats in my care have had to have dental work done. Contrary to what most people have been told by their veterinarian, dry food does not clean teeth!
When a cat chews dry food, it shatters into small pieces. In order to promote effective cleansing of tooth and gums, the food must remain in contact with the teeth and gums for a period of time. Nothing is going to provide effective abrasive cleansing than chunks of raw meat. Unless you are prepared to brush your cat’s teeth or pay hundreds of dollars for dental work, I suggest you start feeding chunks of meat. As I write this, I’m making a note to myself that Ms. Bella, the resident lazy chunky-monkey, chowhound is going to go on an all-chunks diet regimen for a few weeks. Cats are not thirst driven like dogs and are able to survive on less water than dogs. They compensate for reduced water intake by concentrating their urine. HALF the amount of water compared with a cat eating canned foods. On a dry food diet, a cat’s urine becomes overly concentrated which leads to feline lower urinary tract disease. Fat, dry-food-fed cats are prone to all sorts of diseases! Urine that is too acidic provides a good environment for oxalate crystals to form that can cause urinary obstruction. Struvite crystals, associated with an alkaline urinary pH were once the common form of urinary tract disorder, now calcium oxalate crystals, associated with a more acidic urinary pH, are more common.