Adding to the above and previous statements - having cleaned out the digestive tract by fasting the dogs are better able to absorb what is fed to them on days not fasting. I have also been told that fasting promotes muscle growth. When the fast is over and food is fed again the body releases growth hormones. I have been raised fasting myself. Not always once a week but I fast often. My girlfriend thought I was torturing my dogs because she had never heard of it but her old couch potato house dogs are ancient looking at half the age of our hunting dogs, excersizing and yes fasting. However, dur