WASHINGTON (UPI) -- The Smithsonian's National Zoo said zookeepers have stepped in to care for a newborn giant panda after the mother showed a preference for its larger twin.

The zoo, where giant panda Mei Ling gave birth to the twins Saturday, said in a Facebook post the mother panda has shown a preference for the larger of her twins. Attempts to switch out the cubs to give the smaller panda time with its mother have failed thus far.

The post said the smaller cub's "behaviors are good" and it has been urinating and defecating well, but zookeepers are concerned about the cub's fluctuating weight, as rapid weight changes are unusual after the first 48 hours of the cub's life.

"The most important thing for the panda team is to help the cub get enough fluids and nutrients. To accomplish this, they are bottle and tube feeding the cub. The cub has shown some signs of regurgitation which can lead to aspiration in such a tiny creature. To be prudent, the veterinarians are administering antibiotics to prevent possible infection," the zoo said.

Officials said their panda team is receiving help from Asia Trail keepers, additional veterinarians and a panda keeper from Zoo Atlanta to ensure the newborn cubs remain healthy.

"The entire Zoo community appreciates the outpouring of well-wishes from around the world," the Facebook post said.

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