The National Zoo’s 6-day-old panda cub passed away last month because its liver cells were dying, possibly because of problems with the baby panda’s lungs, the National Zoo announced this morning.

The panda cub’s lungs were not as developed as they should have been, according to Dr. Suzan Murray, the zoo’s chief veterinarian, who said lack of oxygen was the likely cause of the liver cell death. The undeveloped lungs could be a sign that the female panda cub was born prematurely, according to Murray.

The zoo and Chinese officials will have discussions later this fall about the whether the zoo’s two pandas, female Mei Xiang and male Tian Tian, will be switched out for another pair.

It’s already clear, though, that Tian Tian will likely not have another chance to breed. In the future, the zoo will look elsewhere for panda semen to inseminate Mei Xiang if she remains in D.C., according to Dr. Don Moore, an associate director at the zoo. “He’s not really competent,” he said.

Panda mother Mei Xiang’s behavior has almost returned to normal, according to zoo officials, with her eating about 80 percent of her usual food. She had been nursing a Kong toy since the cub’s death, but has recently ignored it, according to Moore.

Photo by National Zoo used under a Creative Commons license