In a cat’s diet, meat is one normal source of taurine, an amino sulfonic acid. Other foods containing a good source of taurine includes raw chicken liver and roasted turkey (dark meat).
In 1963, when the manufacture of pet cat food was less sophisticated, there was a spate of blindness in domestic cats which the experts decided was caused by a deficiency of dietary taurine. They had thought that the blindness was due to an inherited defect. Taurine deficiency due to a poor diet can still affect cats.
Taurine deficiency in cats is a gradual process leading to progressive retinal degeneration. It may be unnoticed until the damage to the light-sensitive cells, the rods (night vision) and cones, has become advanced and irreversible.
The reason cats require dietary taurine is because they can’t synthesise enough of the amino acid “to meet demands for bile acid conjugation and tissue metabolism, especially those of muscle and central nervous system“.
The other major symptom of taurine deficiency is dilated cardiomyopathy, a disease of the heart muscle. Both this disease and blindness can occur together or the diseases can occur singly.
It seems that they discovered that taurine deficiency caused dilated cardiomyopathy in 1987 and, earlier, in around the middle of the 1960s it was discovered that taurine deficiency caused blindness.
It’s believed that one of the reasons why a cat’s diet is deficient in taurine is because they eat either poor quality food or they eat dog food. Dogs can make taurine through their metabolism from other components in their diet whereas cats can’t. Therefore dog food does not contain a taurine supplement. If a cat eats dog food consistently within 10 weeks of starting on the diet the cone receptors of the retina begin to deteriorate.
After about 20 weeks many of the cones are dead. Then the rod receptors are affected. Both eyes are affected symmetrically and the end result is complete blindness.
Quote in italics is from Nutritional Problems in Cats: Taurine Deficiency and Vitamin A Excess by: K.C. HAYES Harvard School of Public Health, Boston, Massachusetts 02115 and The New England Regional Primate Research Center, Southborough, Massachusetts 01772.
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