Concerns about the safety of milk and other dairy-based food products spiked recently following the discovery that large volumes of Chinese milk, much of it exported, had been chemically tainted by its manufacturers.

The tainted milk caused several deaths and sickened tens of thousands of infants who were fed milk-based formula. Chinese health officials say the problem has been corrected, but the incident underscores the value of improved milk safety systems. 

In the northeastern American state of New York, researchers at Cornell University's veterinary college are working with American dairy farmers to keep bacteria and other contaminants out of the U.S. milk supply. Reporter Véronique LaCapra has the story.

New York State is home to more than six thousand dairy farms, with cow herds ranging in size from just 20 to several thousand. In a state that produces almost five and a half billion liters of milk each year, milk safety is a top priority.

Ynte Schukken is the director of Cornell University's milk quality program. His staff goes out to dairy farms, checks milking equipment, and takes milk samples. Laboratories then analyze the milk for bacteria and other pathogens. Once his veterinarians have the results of the equipment and milk testing, they help farmers solve any existing problems and keep new ones from developing.

Mastitis: Dairy's Worst Health Problem, Worldwide

One particular problem for dairy cattle is a bacterial infection called mastitis. According to Schukken, mastitis is a worldwide issue.

"Every place I have worked - and that's Asia, Africa, Europe, America, South America - mastitis is typically the number-one problem of dairy farmers," he says. "And it really doesn't matter if you milk by hand or you milk with a machine, or you have a thousand cows or you have two cows. There is always a very high risk."

Mastitis causes an inflammation of the mammary glands in a cow's udder. The milk from an untreated cow is still relatively safe to drink, but it's full of white blood cells that form unappetizing clots and flakes and make the milk go sour more quickly. The more cells in the milk, the lower the price that farmers can get for it. Too many cells, and they can't legally sell it at all.

Schukken says that for the dairy farmer, the biggest cost of mastitis is the loss of milk production - and in some cases, the loss of the cow.

"Approximately 10 percent of cases are so severe that the cow will either die or won't come back into good production again," he says.

In most cases, though, mastitis can be treated with antibiotics. Since U.S. law prohibits antibiotic residues in milk for human consumption, dairy farmers have to throw away the milk a cow produces during treatment - yet another cost of the infection.

Expert Emphasizes Hygiene as Key to Preventing Mastitis

Schukken stresses that he prefers to help farmers prevent mastitis rather than have to treat it. The best way to prevent the disease is surprisingly simple: keep the cows clean. Good hygiene practices should include keeping the cows' stalls and pasture clean, says Schukken.

"The cleaner the better, obviously," he says.

Since most U.S. farmers now milk their cows by machine instead of by hand, the hygiene of the milking machine - and the cow's udder - is also critical.

"In the U.S., we require that before milking, the teats get disinfected with some sort of a chemical disinfectant like iodine," explains Schukken. "And then they're cleaned before the unit - the milking unit - is put onto the cow."

Inside the milking parlor at the Sunnyside Farms dairy in Genoa, New York, the mechanical roar makes conversation difficult. With a hose attached to each of the cows' teats, the milking machines mimic the motions of hand milking.

If you listen closely, you can hear the hoses pulsating. "Left-right, left-right, left-right!" Schukken's gestures follow the movement of the hoses.

"So this is the continuous dance of the unit, of suction to get milk out, and massaging to release fluids and all that from the teat-end," he says.

"If you have this nice rhythmic noise," he adds, "it means things are working well."

At Sunnyside, two thousand eight hundred cows are milked three times a day, producing more than 100 thousand liters of milk.

In the milking parlor, the cows - about 100 at a time - file into stalls on two, long, elevated platforms, which are separated by a wide center aisle. Workers move quickly down the stalls, cleaning the cows' teats and attaching the milking hoses.

"It's five people having to do about 52 stalls," describes Schukken. He says the goal is to milk one side of the parlor in about 15 minutes. "So it's all a game of time."

At that pace, the workers milk 400 cows an hour for eight hours a day. "So it's a continuous rotation here, to be able to milk the cows all the time you need to have a very efficient process," he says.

Bulk Tank Monitoring Can Help Protect Milk Safety

From the milking parlor, the milk is collected and stored in large refrigerated tanks, called bulk tanks. Each tank holds about 45 thousand liters of milk.

Schukken says the milk is stirred continuously inside the tanks. "So if you take a milk sample from the top - there is a little ladder here, and there is an opening in the top - if you take a milk sample from the top, it's quite a good representation of the total milk in the farm."

By collecting fewer than 100 milliliters from the bulk tank, dairies can reliably test their milk for bacteria, viral diseases and food safety pathogens. The system is efficient, inexpensive and new.

"We're developing it in collaboration with the Department of Homeland Security," he says. Schukken explains that the same infrastructure could be used to monitor for any disease that might come into the country.

As a means of ensuring milk safety, Schukken sees a lot of promise in the bulk tank monitoring system for individual dairies and for milk-producing countries worldwide.