The world's largest private rhino breeder, John Hume, has started selling off 500 kilos of rhino horn in a three-day online auction. 

The controversial sale of 264 horns comes after Hume won a court case against the South African government to overturn an eight-year ban on the domestic trade of rhino horn. 

Hume, who has tonnes of stockpiled rhino horn, said the money he stands to make from the auction is vital to help cover the high price of protecting his rhino herd on his sprawling game reserve west of Johannesburg. 

Security teams, helicopter patrols, infrared sensors and electric fencing cost the breeder $170,000 (144,100 euros) a month. 

"If I don’t sell rhino horn, in ten years’ time, my 1,535 rhinos out there are all going to be dead," he said. 

"The people who are stopping me from selling my rhino horn and protecting my rhino may as well be joined with the poachers because they will kill my rhino," he said. 

Hume harvests the horns by tranquilizing the animals and cutting them off – a technique he says is humane. Until the horns grow back (which takes about two years), it also protects his animals from being slaughtered by poachers eager to cash in on the voracious Asian appetite for rhino horns. 

Global trade in rhino horn was banned internationally in 1977 but the animal remains critically endangered. 

A vast syndicate of smugglers sells the horn in Vietnam, China and elsewhere in Asia, fed by poachers in Africa. 

Rhino horns mainly consist of keratin, a substance found in human nails, and are sold in Asia in powdered form as a purported aphrodisiac and also as a supposed cure for cancer and other diseases.

In 2016, poachers killed 1,054 rhino in South Africa, home to around 70 percent of the 30,000 rhinos left on earth. 

A decade ago, only 13 rhinos were killed in the country. 

Hume and other rhino breeders say the dwindling rhino population is proof that the international ban on buying and selling rhino horn isn't working and are calling for regulated trade to slash poaching. 

“We have had an international trade ban for 40 years and haven't managed to save a single animal," said Pelham Jones, the chairperson of the Private Rhino Owners' Association from South Africa, who also owns a game reserve. 

"Instead we have created an international crime syndicate." 

But conservationists opposed to the auction fear that any rhino horn sold legally in South Africa will be illegally smuggled out of the country, further fueling demand for the product. 

Richard Thomas, a spokesperson for Traffic, an international NGO specializing in wildlife trade, said it was hard to believe that there was a real domestic market for rhino horn in South Africa. 

"The likelihood is that it will supply the lucrative Asian market," Thomas told DW, pointing out that the online auction site was available in Chinese and Vietnamese. 

"The huge price tags attached to rhino horn open up the temptation for people to export it," he said. 

He also said corruption was a major factor facilitating trafficking and perhaps the greatest obstacle to curbing smuggling.

Michele Pickover, Director of the South African rights group, EMS Foundation, called the auction "outrageous“ and accused Hume of being motivated by profit. 

"He has exacerbated the loopholes that we have in our law to trade and farm in rhino. Our rhino should be protected rather than farmed, commodified and traded," she said. 

Additional reporting by Thuso Khumalo (afp)