Ninety-nine percent of a panda’s diet consists of bamboo. This doesn’t really change between the black and white pandas that are typically referred to by the single word “panda” or the red panda. The bamboo has most of the nutrients a panda will ever need - with the few it doesn’t have being supplemented in from other kinds of foliage that are found around where it lives.
Most pandas that live in the wild live in China; the chinesegovernment kind of sees them as their property. So, the pandas seen at many zooes are just being loaned out by the Chinese government. They are often used as a way to get other areas to comply with Chinese censorship of certain topics or to back them up.