Digestibility tests are used to determine how much food is absorbed. It is assumed from this that food "A," because it is 95% digestible, is better than food "B," which is 90% digestible. But that would imply that if food "C" were 100% digestible, with zero fecal output, it would be the best pet food of all.
Not so. Digestive tract health and the movement of food through the intestines where different elements are absorbed, depends upon a portion of food being indigestible. Certain kinds of food components such as fibers and oligosaccharides not only help maintain the health of the digestive tract but encourage the growth of friendly microorganisms that fight pathogens and exert a range of other health effects.
Digestibility tests attach simplicity to that which is incredibly complex. Measuring how much is absorbed compared to how much is lost or excreted says nothing about the merit of what is absorbed. Nutrition is a tissue-level biochemical phenomenon, not a simple subtraction between what is eaten and what is excreted.
Nevertheless, some pet food producers will promote their "best pet food" based upon its digestibility percent. This createS false confidence in a processed pet food so that people will feed it exclusively.
Not only is digestibility not a true measure of value, it ignores that there is no generally accepted method for determining digestibility.
The wise approach to nutrition is to forget the lab tests and experts, feed dogs and cats as they are designed, and let the digestibility chips fall where they may. If your goal is the best pet food, nature has things pretty well figured out and she is the only true expert.
Thought for the day: "Love of animals is a universal impulse, a common ground on which all of us may meet. By loving and understanding animals, perhaps we humans shall come to understand each other." – Louis J. Camuti, D.V.M.
Phrase for the day: 'average life span' - The average number of years a person or animal is expected to live. It factors in infant deaths. Although the average life span has increased, it is not due to modern medical measures, but to decreased infant deaths due primarily to the advent of public hygiene and better food distribution. Plumbers and truckers deserve more credit than doctors.