He said about 42 kg of horn had been stolen, which, according to prices of Vietnamese traditional medicine deals, would sell for about $2.75 million on the streets of Hanoi.
Van Zyl said he had permits for horn removal and storage. South Africa allows for private storage of horns, which must be registered, while forbidding almost all sales.
The thieves broke into a business office on Wednesday evening and appeared to have used a blowtorch to open a safe where the horns were kept, police and the game farm owner said.
“At this stage, we haven’t arrested anybody yet, but we are still investigating,” Limpopo police spokeswoman Colonel Ronel Otto said.
South Africa is home to the vast majority of rhinos on the continent, with numbers estimated at about 21,000.
Last year, more than 660 rhinos in South Africa were killed by poachers – a record high – and more than 800 rhinos could be killed this year if poaching continues at its current rate.
Several game reserve owners have dehorned rhinos to make them less likely to be killed by poachers, while South Africa has deployed its army to protect the animals in national parks.
Rhino horn has been used for centuries in Chinese medicine, where it was ground into powder to treat a range of maladies including rheumatism, gout and even possession by devils