I still don't understand what the difference is between Vitality™ and Geriatrx™. They have the EXACT same ingredients. There doesn't seem to be the variation you're talking about. Please reply.

The formulas differ in type of ingredients (even though they may read the same on the label) and in proportions. With Geriatrx™ we try to improve the protein quality since older animals have a less efficient ability to assimilate protein and begin to break down tissue protein (catabolism) with age.