From the Jan. 14, 2009 Washington Post:

"The zoo this morning is issuing a public appeal for bamboo to feed its famous giant pandas. For a combination of reasons, the zoo's supply of the crunchy green stalks are critically low, and zoo officials said they might not have enough to last the winter.

One problem is that the zoo now has three more or less adult-sized giant pandas -- the main consumers of its bamboo. At 160 pounds, 3-year-old Tai Shan is no longer a cub, and his parents, 275-pound Tian Tian and 250-pound Mei Xiang, are ravenous grown-ups. They scarf up bamboo 12 to 14 hours a day, consuming some 1,400 pounds of the stuff a week."

Here is a link that might be useful: Here's the article