Siberian tiger Katja is seen in the den with her cub before she abandoned it on Tuesday. (Calgary Zoo)

A Siberian tiger cub born Monday at the Calgary Zoo has died of organ failure after being abandoned by its mother, Katja.

The unnamed female cub died at around 7 p.m. Thursday night, zoo staff announced Friday.

"What we do know is that Katja did all she could and we did all we could and, tragically, it unfortunately wasn't enough for this cub, who was clearly born with issues that we couldn't prevent or deal with," Jake Veasey, the zoo's director of animal care, conservation and research, said at a news conference Friday.

Veterinarians performed a post-mortem examination overnight that confirmed the cub succumbed to organ failure after it was unable to absorb nutrients from the food it was given. It had emergency heart surgery earlier Thursday.

The cub was taken to the zoo's animal care centre after it was abandoned by its mother on Tuesday afternoon.

"Although there were small signs that gave us all some cautious hope, the cub had been entirely dependent on human intervention since Tuesday evening and simply was not strong enough to pull through, in spite of receiving the very best of care," Jake Veasey, the zoo's director of animal care, conservation and research, said in a news release.

Katja killed her previous two cubs, born in the fall, by carrying them improperly.

The post-mortem showed no signs of trauma, supporting Calgary Zoo staff's observation that Katja provided proper care in the cub's first 36 hours.

"It appears now that the cub's mother, Katja, may well have detected health issues which ultimately led to the death of the cub," Veasey said in the news release.

Cub sparks controversy

The zoo has not decided whether it will try to get Katja pregnant again.

The birth of the cub and its rejection by Katja has provoked some controversy.

Rob Laidlaw, the founder of Zoocheck, questioned the wisdom of breeding captive Siberian, or Amur, tigers.

Baikal is the father of the cub who died Thursday night at the Calgary Zoo. (Calgary Zoo)

"There's no mechanism for putting these animals back into the wild," he said earlier in the week. "They're really just breeding them to maintain them in zoo displays, and there's not really a lot of conservation purpose."

Laidlaw, who would like to see zoos changed to become more like wildlife sanctuaries, said animals' instincts are often disrupted by captivity.

In the release about the death of the cub, Veasey spoke about some of the issues raised by Laidlaw.

"The conservation efforts to save endangered species depend upon a multi-pronged approach, including captive breeding of insurance populations, conservation efforts in the wild, research and the effective management of human conflict," Veasey said.

There are only about 350 Siberian tigers left in the wild. The survival rate for tiger cubs, both in the wild and in captivity, is one in three, the zoo said.

The Calgary Zoo has four adult Siberian tigers, including the cub's father, Baikal. One will be sent to the Toronto Zoo as part of the co-ordinated species survival program for the tigers.