The cellulose molecule is just a long string of glucose molecules, but paradoxically, cellulose is an indigestible fiber, whereas glucose is the most easily digestible of all foods. I don’t know how to calculate the number of Big Gulp units in a pair of cotton socks, but it should be easy to do.
There’s no paradox here for cows, however. Not only is the bovine mind blind to paradox, but even intelligent bovids wouldn’t see what the fuss was all about, since cellulose is their primary food. This alleged food / fiber paradox is merely an artifact of our inferior digestive system.
Because cellulose is hard to digest, cows must perform a complicated series of chemical procedures in their enormous gut system. If cows were genetically modified to live entirely on glucose, they would be more svelte, but I doubt that they’d be any smarter.