Im not sure but it may have something to do with the cow being domesticated and raised specifically for human consumption. plus panda bear meat probably tastes nasty. plus it would be difficult to raise and domesticate a panda for human consumption unless it goes through the mutations that domestication causes. the hide would be better though.
In India (and other Hindu cultures) it is NOT okay to eat a cow. ~ However, for thousands of years in most parts of the world, cows have been raised FOR food. Cattle are bred exactly for this reason. They are not wild animals like a panda. ~ Different cultures eat different things and view animals other than we do. In North America and Europe, dogs and cats are pets. In other parts of the world, they are food. In Peru they eat guinea pigs. ~ How is it that you have decided that we do not need pandas? The world needs all of it animals, including the vile cockroach. Each animal/organism plays a small part in how the world operates. It may not be something we can see, feel, or touch, but that does not mean that it isn't there.