Tian Tian has been artificially inseminated again after failing to produce a cub despite several previous attempts.
Vets believe she may have conceived last year but “resorbed the pregnancy”, which is common among giant pandas.
However, on Sunday she was implanted with semen from male panda Yang Guang after hormone testing showed she had reached her short breeding window.
Iain Valentine, director of giant pandas, confirmed that veterinary staff, experts and panda keepers had carried out the procedure again.
In a blog post, he said: “Unfortunately Yang Guang wasn’t receptive to natural mating this year – turning the tables on Tian Tian for a change, whose behaviour suggested she wanted to be mated.
“Although we’ve tried a number of times now to see if the pandas will mate naturally, it’s important to approach every year afresh as animals are by their very nature unpredictable and their behaviours can change from year to year. In the early evening, we then prepared to give nature a helping hand by performing an artificial insemination procedure.
“With our Chinese colleagues from the China Conservation and Research Centre for the Giant Panda, Tian Tian was implanted with semen from our male Yang Guang by experts from the Leibniz Institute for Zoo and Wildlife Research, a complex procedure which was undertaken with great skill.
“We continue to believe that it’s important biologically for Tian Tian, a female in her prime, to breed and reproduce and add to a vital ex-situ population outside of China.
“If we can successfully assist Tian Tian to carry to full term, we have no doubt that she’ll be an excellent mother and both our male and female’s genetics will be preserved in future giant panda generations.”
Tian Tian and Yang Guang were loaned by the Chinese government, at a cost of around £600,000 a year, but have yet to successfully mate while in Scotland.
Panda reproduction is a notoriously tricky process with females only ovulating once a year with a gestation period typically lasting five months.
Pandas practice delayed implantation where the fertilised egg will not implant into the uterus until some time after conception, as the embryo is still in a period of suspension.
The procedure had been carried out in each of the last three years but Tian Tian has so far been unable to produce a cub.
Experts stressed that it would be some time before they would know if Tian Tian has conceived and even longer before they would know if she had gone on to be pregnant.
“There are many hurdles to go through yet and until birth takes place, all giant panda conceptions are complex and uncertain,” Mr Valentine said.