Female panda cub died of insufficient oxygen to liver

Scientists at the National Zoo say a necropsy shows that a 6-day-old female giant panda cub died last month from insufficient oxygen to its liver because of lungs that were not fully developed.

Update at 10:40 a.m. ET: Washington zoo officials say the current agreement with China regarding the two pandas, which are on loan, runs through 2015, but could provide for replacing one or both of the adult pandas over issues of breeding in the wake of the cub's death.

Discussions on the agreement will be held this fall, zoo officials say.

Update at 10:29 a.m. ET: Zoo officials also say that the cub's mother, Mei Xiang, and father, Tian Tian, are returning to their normal routines.

"We are happy to report that Mei is almost completely back to her old self! Her hormones have returned to normal levels, as has her behavior. Mei is choosing to go outside in the mornings. In the afternoons she can usually be found napping on her indoor rock work," the zoo said.

The offiicals say Mei's appetite has also returned, and that she is eating "almost all of her bamboo and all of her leaf eater biscuits and produce."

Update at 10:25 p.m. ET: The National Zoo, in a statement on its website, says that its final report confirms the results of the preliminary necropsy that found fluid in the tiny cub's abdomen and that her liver was hard in places:

There were no signs of internal or external trauma. The final necropsy determined that lung and liver damage ultimately caused the cub's death. Her lungs were poorly developed and likely caused her to have insufficient oxygen, which would be consistent with the changes in the liver. The mortality rate for pandas in their first year in captivity is estimated to be 26 percent for males and 20 percent for females. Some early mortality rates may be underestimated.

Update at 10:12 a.m. ET: National Zoo scientists say that a panda cub's death six days after it was born last month was caused by insufficient oxygen to its liver.

Suzan Murray, chief veterinarian for the National Zoo, tells reporters Thursday that the cub's lungs were not fully developed and that that complicated the delivery of oxygen to the cub's liver.

"The lungs certainly weren't able to pick up and the blood cells unable to deliver" the oxygen, says Murray.

Original post: A preliminary necropsy revealed that the tiny cub had liver abnormalities and fluid in its abdomen, the Associated Press notes.

The cub, believed to be female, was born Sept. 16. The birth was a surprise because it hadn't been clear whether mother Mei Xiang was still fertile.

The zoo will also offer provide an update on Mei Xiang. Her behavior has slowly returned to normal after the cub's death.