A zoo in Denmark that was met with an international outcry after it killed a healthy giraffe because of its breeding procedures, has put down a pair of adult lions and two cubs.

Citing the “pride's natural structure and behaviour,” Copenhagen Zoo said on Tuesday that two old lions had been euthanised as part of a generational shift.

It added that the cubs were also put down because they were not old enough to fend for themselves and “would have been killed by the new male lion.”

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Copenhagen zoo officials hope the new male and two females born in 2012 will form the nucleus of a new pride.

The deaths come after Copenhagen Zoo ignored pleas from international campaign groups last month and killed a healthy giraffe named Marius.

To prove they were certain of their actions, after shooitng Marius in the head, zoo staff dissected him in front of a public crowd, including children, and fed him to the zoo's lions.

At the time, the zoo's scientific director, Bengt Holst, said it was working to maintain “a healthy giraffe population in European zoos.”

“This is done by constantly ensuring that only unrelated giraffes breed so that inbreeding is avoided. If an animal’s genes are well represented in a population further breeding with that particular animal is unwanted,” he said in a statement.

Marius’ genes were “well represented” and there was “no place” for him in the zoo’s herd, so it had been decided in conjunction with European Association of Zoos and Aquaria officials that it would be acceptable to kill him.

Groups including British-based Captive Animals Protection Society, Denmark’s Organisation Against the Suffering of Animals, and Animal Rights Sweden all came out against Marius' death in February.

Additional reporting by AP