An Orana spokesperson said Mdomo the giraffe "tragically passed away" on Friday afternoon following a general anaesthetic the week before.
The loss of Mdomo was compounded by the death of five-month-old zebra foal, Zeeyore, at the park earlier this month.
"Mdomo had developed a notable lump on her right cheek, suspected to be a feed impaction resulting from an underlying dental issue, and our team observed a gradual decline in her behaviour.
"A detailed protocol for the GA was developed over many weeks in consultation with the veterinary team at Rangiora Vet Clinic owing to the risks of anaesthesia, particularly for a large mammal.
"The procedure involved a multi-disciplinary team of four vets and twenty Orana staff members each with special roles.
"The procedure went to plan with a full clinical examination carried out, as well as blood sampling, head and dental radiographs, oral inspection and hoof check, though there was no definitive cause identified for the impaction issues."
Mdomo initially recovered well from the procedure. But two days after the general anaesthetic her condition declined and she slowly deteriorated over the week, despite multiple vet visits, a treatment plan, and the best efforts of the Orana team.
"Sadly, her condition worsened on Friday morning and following further vet inspection, the team made the kindest decision to euthanise Mdomo," the spokesperson said.
A post-mortem indicated the decline in Mdomo’s health was due to a significant reduction in gut movement, which can be a complication following sedation.
"The Orana team, and especially those who worked closely with her, were deeply connected to Mdomo, and are reeling from the loss of this beautiful animal.
"It will take time to process her passing. Mdomo has been a much-loved member of the Orana whānau since she arrived from Auckland Zoo in 2016.
"Many thousands of visitors have had the pleasure of meeting her and hand feeding this gentle giant."
"Zeeyore was under constant veterinary monitoring since birth and our dedicated animal care team worked tirelessly with Zeeyore to supplement his feed, but he sadly never progressed," the Orana spokesperson said.
"The post-mortem revealed that mis-mothering may have been the main cause of his passing.
"He had a history of failing to thrive since birth and was weaned early by his first-time mum, which sadly led to his premature passing.
"His name was inspired by Eeyore for his gentle, quiet spirit. Earlier this year, we announced the arrival of Herbie and Zeeyore - the first zebra foals to be born at Orana in 30 years.
"Zeeyore has left a lasting impression on the team, and he will be dearly missed."
