Melbourne Zoo’s beloved Asian elephant bull Bong Su has died after a lengthy battle with a degenerative joint disease.

The 43-year-old giant was euthanised on Monday after his condition deteriorated and medications and treatments could no longer keep him comfortable, the zoo said in a statement.

He has been under treatment for arthritis since 2005, when he was first diagnosed with degenerative joint disease.

Vets had recently increased his pain relief treatment, anti-inflammatory drugs, massage, and laser therapy, but in the end he was suffering too much.

Zoo director Kevin Tanner said it was a tough decision and euthanasia is only ever a last resort “to end or prevent an animal’s suffering”.

Sadly today we said goodbye to bull #elephant Bong Su. You will be missed buddy #valebongsu #melbournezoo More: https://t.co/JV4slwWesp pic.twitter.com/QJBMuZuhz9

— Zoos Victoria (@ZoosVictoria) October 9, 2017

Bong Su, meaning the last born member of a family in Malay, came to Melbourne as an orphan in 1977 from an elephant camp in Malaysia as a gift from the Sultan of Pahang.

He sired five calves via artificial insemination, four in Melbourne and one at Sydney’s Taronga Zoo.

His first calf was the female Mali, now seven, who was the first elephant calf ever born at Melbourne Zoo.

The zoo has arranged counselling for staff who it says are experiencing a great sense of loss.

-AAP