Slobodan Simic hardly looks like a donkey farmer. A 62-year-old lawyer and former lawmaker in the Serbian parliament, he's in dark glasses, chomping on a tobacco pipe.
"Jesus rode to Jerusalem on a donkey," he says. "They're special creatures, and that's why everyone in Europe used to have one. Ours was the Balkan donkey, and I want to preserve it."
About 20 years ago, Simic gathered scores of underfed donkeys that were no longer useful on farms and brought them here to what the Serbs call the Zasavica nature reserve, located 50 miles from the Serbian capital, Belgrade. At 4,500 acres, it's one of the last wetlands in Serbia. Simic runs an environmental nonprofit that manages the reserve, a popular destination for local tourists. He also uses part of the land as an animal farm that now has 200 Balkan donkeys as well as Balkan breeds of cattle (podolian) and pig (mangulica).
With his 200 donkeys, Simic runs the largest donkey farm in eastern Europe, producing roughly 8,000 liters of milk a year. (A female donkey, called a jenny, only lactates when her foals are nearby and only for about six months of the year.) He sells the milk and several donkey-milk-based products, including soaps and face cream, to local distributors and tourists.
At first, he had trouble convincing people to try it. Even his friends, like translator Julkica Djurdjevic, were skeptical.
"When I don't know something, I don't want to try it," she says, standing next to a wooden donkey sculpture near the farm. "Really, I was a total skeptic. I'm talking (to myself), 'if you don't like you can spit it out.'" But she didn't have to. "For me, it was tasting good."
Simic's right-hand man, Jovan Vukadinovic, a garrulous retired air traffic controller who's the assistant manager here, ushers us to a picnic table and offers us coffee, donkey-milk liqueur and sausages made out of a few of the pigs. "In the mouth, like chocolate, it is melting," Djurdjevic says of the sausage.
Vukadinovic says while researching ways to make money to help support the reserve, the staff read that dairy entrepreneurs around Europe were using donkey milk to make everything from infant formula to beauty creams.
"We started to milk them and sell milk because that is medicine," Vukadinovic says.
"It has 60 times more vitamin C than a lemon," he claims. "And it is almost similar to mother's milk. You immediately can give it to baby." Italian researchers have come to the same conclusion, recommending it for infants allergic to cow's milk.
They sell the milk at the farm, sometimes freshly milked from the donkey. Vukadinovic guides me and a Serbian journalist, Darko Jevtic, to a shaded stall where a few female donkeys, cuddling with their foals, or eating hay. A reserve staffer hands us a glass of creamy milk, which we share.
"What do you think it tastes like?" I ask Jevtic, who drinks first.
"I don't remember mother's milk," he deadpans. "Maybe when my wife is pregnant I will know."
I find it light and sweet, like almond milk. Just seven fluid ounces (about a cup) costs eight euros, or about $9.
It's not selling as well as it should, Vukadinovic says, largely because most people here can't afford it. The average monthly income in Serbia is around $430 a month.
The Zasavica farm does receive a small subsidy from the government, which, combined with modest sales, is enough to keep the donkeys fed and happy and the 12 employees here paid.
There's a reason why donkey milk is so expensive, says Pierliugi Christophe Orunesu, who runs Eurolactis, an Italian- Swiss company specializing in donkey-milk products. Donkeys produce just about 70 fluid ounces of milk a day, compared to cows, which produce up to 25 times as much, he says.
Orunesu started his company in 2008, partnering with an Italian farmer who had 280 donkeys. He was drawn by what he calls the "origin story" of donkey milk: That Hippocrates used it to heal wounds, that Cleopatra is said to have bathed in the milk of 700 donkeys to keep her skin supple, that hospitals used to give it to babies until the late 20th century. He claims Pope Francis drank it as an infant.
"There is a taste of caramel or sugar because it's rich in lactose," Orunesu says. "It's very easy to digest, and it's very easy to drink."
And he has succeeded in turning donkey dairy into a thriving business. Now the farm, based near Parma in northern Italy, has more than 680 donkeys, and partnerships with other donkey farms have brought the herd to more than 950.
Eurolactis sells its donkey milk products worldwide, including powdered infant formula, beauty creams, chocolate bars and even a version of donkey-milk Nutella.
(Powdered donkey milk is also a product of a Greek company, Hellenic Asinus Farms, which is also gaining a get a foothold in the industry.)
What Orunesu's never tried to make is donkey cheese. It's too expensive to do using only donkey milk, he says. The few who have tried usually add goat milk to make it cost-effective.
But not Slobodan Simic, the Serbian conservationist. A few years ago, he and a Belgrade cheesemaker partnered to develop a crumbly, lightly salty cheese made from the milk of Zasavica donkeys.
It's since won fame as the most expensive cheese in the world, surpassing Swedish moose cheese. He says rich Russian businessmen and Ukrainian bankers traveling in Serbia show up at the farm to buy the cheese.
Simic brings me a tiny golden pyramid-shaped carton embossed with "donkey cheese." Inside is 1.7 ounces cylinder of donkey cheese. I break off a tiny piece; it's mild and rich.
"It costs 50 euros (about $54)," Simic says. A pound costs about a $560.
He explains that it takes about 900 fluid ounces of donkey milk to make about 2 pounds of cheese. That's a little more than half the amount of milk produced annually by each donkey on the farm.
Simic says he's gotten requests for his cheese from turophiles in Austria, Germany and Switzerland. But he can't mass-produce the cheese, nor can he export it, because donkey milk is not on the Serbian Agriculture Ministry's official dairy list, which now only includes cow, goat and sheep milk.
Those who want to sample the world's most expensive cheese, or buy any Zasavica dairy products, have to travel to this Serbian bog.
If Simic ever gets permission to open a donkey-cheese factory, he says he will sell the world's most expensive cheese to the highest bidder. Until then, he says he plans to keep selling Zasavica donkey milk and its products to whoever shows up at his farm.
Joanna Kakissis covers Greece and the Balkans for NPR. Follow her on Twitter at @joannakakissis.