Two Pandas Failed to Mate at National Zoo

Two pandas, Mei Xiang (female panda) and Tian Tian (male panda), at the National Zoo in Washington DC attempted to mate. Panda mating emphasizes on timing, and panda only made one day in a year.
The two pandas attempted to mate on Saturday night. The two pandas were observed and later determined that the mating was not successful. Both pandas were then anesthetized so that semen could be removed from Tian Tian and artificially inseminated Mei Xiang. The zoo had tried to conduct artificial insemination last year but the attempt was not successful. Mei Xiang and Tian Tian were successfully inseminated artificially in and gave birth to a cub, Tai Shan, in 2005.
Source: msnbc

The size of the surviving panda is also an issue, and it is still smaller than the kittens that were born later than it. It will only be slightly larger than a cat when it survived to be an adult.