MELBOURNE Zoo’s beloved bull elephant Bong Su has died, 40 years after his arrival in Victoria.

The Asian elephant was euthanised after a long-running battle with arthritis beginning 2005, with the zoo giving him pain relief treatment, including additional analgesic agents, increased dosage of his anti-inflammatory medication, massage, and laser therapy.

media_camera A young Bong Su, aged two, when he arrived at Melbourne Zoo in 1977.

media_camera Curious Melbourne zoogoers check out the baby Bong Su in 1977.

media_camera Bong Su, pictured as a baby, was a gift from the Sultan of Penang.

But zoo director Kevin Tanner said the heart-wrenching decision was made to “end” the senior elephant’s suffering.

Zoo head veterinarian Dr. Michael Lynch worked with Bong Su for many years and determined that the elephant was beginning to experience an unacceptable level of pain.

The orphan Bong Su arrived at Melbourne Zoo in 1977 from an elephant camp in Malaysia and was a gift from the Sultan of Pahang.

media_camera Bong Su with fellow elephant Barbara in 1981.

media_camera A keeper cooling Bong Su down in 1989.

He sired five calves — four at Melbourne Zoo and one at Taronga Zoo in Sydney.

His first offspring was the female Mali, now seven years old, who was the first elephant calf ever born at the zoo.

All five calves were born via artificial insemination.

Mr Tanner said zoo staff were experiencing a great sense of loss, especially among current and previous elephant keepers.

media_camera Bong Su, aged 24, tucks into his meal. media_camera The elephant sired five calves. Picture: David Caird

media_camera Bong Su celebrated his 40th arrival anniversary in February. Picture: David Caird

Counselling has been offered to zookeepers and staff members.

Bong Su’s death comes after the zoo’s last surviving lion, Harare, was put down in January.

The big cat’s two brothers Chaka and Zuri also died late last year from an age-related degenerative neurological condition.

Vang the white gibbon died of old age in March, and the zoo’s most famous gorilla, Mzuri, died in a French zoo in May.