As a 5-year-old on his family's farm in the Netherlands, Harm Kiezebrink wondered why his father instructed him to drown newly hatched male chicks in a large plastic drum inside the hatchery.

The answer: Male chicks are slaughtered because they won't be able to lay eggs and because they will be too scrawny for meat.

Today, the family company sells killed chicks to zoos and falconers. And it is developing technology for efficiently killing birds.

Mr. Kiezebrink grew up to become an expert in this unusual field and has taken his skills to some places that need them urgently: Asian nations fighting bird flu. He has also brought them some of his bird-slaughtering machines, such as the AED-100, which kills about 10,000 birds per hour, catching them by the feet and dragging their heads through an electrified pool of water. "If you want to kill one million chickens in an hour, how the hell do you want to do it?" he says. "By hand?"

There is fresh demand these days for killing lots of birds quickly. Avian influenza, a disease that afflicts birds but that can also infect and kill human beings, is on the loose in Asia. Though there is no evidence that the virus is able to spread easily between humans, scientists believe it could mutate into a form that could cause a world-wide pandemic. Health authorities have taken to responding to outbreaks by ordering farmers in surrounding areas to kill their chickens, ducks and geese. Millions of birds have been destroyed.

That hasn't been easy to accomplish. Overwhelmed farmers have stuffed their birds in sacks and beat them, buried them alive or tried to set them ablaze. But Mr. Kiezebrink is an expert. "He's one of Europe's, if not the world's, most prominent chicken killers, for want of a better word," says Roy Wadia, a spokesman in Beijing for the World Health Organization, which has worked with him in China.

In the past two years, he has worked with health officials from nearly a dozen countries, including the U.K., France, Portugal, Spain, Mexico, Vietnam, China and Thailand, on how to safely and quickly eradicate birds that may have been exposed to flu.

Mr. Kiezebrink's consulting work has also provided him with a convenient platform for his efforts to sell his bird-killing machines. So far, they have proved to be too expensive -- as much as $600,000 -- for those prospective customers.

Mr. Kiezebrink says his work is driven by a strong and very personal passion: His father, also a bird man, died in 1997, at the age of 64 of a mysterious flu that Mr. Kiezebrink is convinced was avian.

Mr. Kiezebrink, who is 46, didn't plan on a career in poultry. Though he didn't tell anyone at the time, he says that as a boy he was horrified at having to drown chicks. He says he grew up resenting the farm his family had worked on for more than a century.

His 72-year-old mother, Anky Kiezebrink, remembers that drowning the chickens did bother her son. "He was always trying to think of another way to kill the chickens," she said in a telephone interview from her home in Putten, Netherlands.

When he turned 17, he left the farm to study mechanics and for a time worked on a tanker transporting chemicals between northern Europe and Russia. He was sure he would never have anything to do with chickens again. "I wanted to get out of there as soon as possible," he says.

After a string of jobs in his early 20s, he ended up as a insurance consultant. But in 1995, after 20 years away from the farm, his father called him, and asked him to return to help the family business.

His mother wasn't surprised he returned. "It is in our blood, chickens," she says. "We were born with chickens."

So he went to help his younger brother, Hanno. The company, Kiezebrink International, based in Putten, kills male chicks just a few hours old, freezes them, and ships them to zoos around Europe to feed to birds of prey such as owls and falcons. A kilogram of frozen chick costs about $1.20, and the company shipped about 35 million chicks last year.

In 1997, his late father, who had traveled often to do consulting work on other farms, went to teach the workers on a farm in Indonesia how to determine the sex of chicks just a few hours old.

Upon his return, he came down with a flu-like illness. He quickly developed a very high fever. Twelve days after arriving home, he died.

What exactly killed him was never clear. Knowing that he had been in contact with poultry in Indonesia, Dutch health officials investigated the death, and sent the father's organs to a laboratory in Rotterdam for inspection. The investigation was inconclusive, the Kiezebrinks say.

But Mr. Kiezebrink is convinced avian flu was the culprit. His father's death has injected an emotional element into his work consulting for countries now under threat. Mr. Kiezebrink is even known to get tears in his eyes while lecturing on bird-flu safety, according to a former colleague.

Soon after his father's death, Mr. Kiezebrink established a chicken-culling consultancy in his name. The Herman Kiezebrink Institute, a for-profit company in Wageningen in the Netherlands, now has 120 chicken-killing machines and about a dozen employees.

Mr. Kiezebrink and his new organization were called into service in 2003 when there was major outbreak of bird flu in the Netherlands and officials ordered a mass slaughter.

Together with other contractors, Mr. Kiezebrink killed more than 40 million birds in the Netherlands and Belgium in about two months. Mr. Kiezebrink had done a handful of kills during local salmonella outbreaks using a new carbon dioxide-based slaughtering machine, but the big Dutch kill raised his profile.

Since then, Mr. Kiezebrink has been called on frequently. In early 2004, he worked with the Food and Agriculture Organization of the United Nations in Thailand and Vietnam, both of which are wrestling with frequent outbreaks of the virus.

In early 2004, Chinese health officials were wrestling with an outbreak of bird flu in Jiangxi province, and flew in representatives from the WHO, including Mr. Kiezebrink, to assess their culling efforts. He suggested the use of sentinel animals in flocks to gauge whether vaccines given chickens are working and advised officials to cover dead chickens with calcium hydroxide and more than 30 centimeters of dirt to prevent further infection.

WHO officials say they were aware Mr. Kiezebrink has attempted to sell his machines while also serving as a consultant, but didn't see a big problem with that. "It's a field that has very few experts at that level," says Mr. Wadia, the organization's China spokesman.

Mr. Kiezebrink also pitched officials on his AED-25, a mobile unit that electrocutes the birds, for around $60,000, promising that it would deliver better and more efficient results. Chinese officials were interested, but the price of the machine was too high, according to Xie Donghui, an official with Nanchang Veterinary Bureau in Jiangxi province who sat in on Mr. Kiezebrink's presentation.

Lately Mr. Kiezebrink has been focusing on developing a less-expensive version of his machine to sell the Chinese. His hopes to land a big sales contract for the dozens of culling machines he has in a warehouse. But his nightmare is that avian flu sweeps the globe, and he carries a stash of the anti-flu drug Tamiflu with him everywhere. "You pay with your life if you make a mistake," he says.