This is the VOA Special English Agriculture Report.
Cows, sheep, goats and other animals can get mastitis, an inflammation in the udder, the organ where milk is produced.
Milk from an untreated cow is still relatively safe to drink. But the milk is full of white blood cells that thicken and make the milk go bad more quickly. Goat milk, though, might still look normal.
The more cells in milk, the lower the price that farmers can get for it. In the United States, if milk contains too many cells, it cannot legally be sold.
One sign of mastitis is cracked skin on the teats. Also, the udder becomes hot, painful and enlarged, and the animal may not eat.
Mastitis can spread as a bacterial infection. So infected animals should be milked separately from uninfected ones. Flies can also spread the bacteria.
About ten percent of cases are so severe that the cow dies or never returns to good production. But antibiotics can treat most cases.
American farmers have to throw away milk produced during treatment because of rules against antibiotic residues in milk.
Ynte Schukken at Cornell University in Ithaca, New York, says the best way to prevent mastitis is to keep the animals clean. The same is true for milking machines, milking areas and pasture lands -- the cleaner the better, he says.
Milkers should always wash their hands. And, in the United States, teats must be disinfected with iodine or other chemical disinfectant before milking. And then they are cleaned before a milking device is used.
Teat injuries can also cause mastitis, so be careful during milking.
Ynte Schukken says mastitis is commonly the number one problem of dairy farmers worldwide. But lately other concerns about the safety of milk products have increased. This follows the discovery of a poisonous industrial chemical in large amounts of Chinese milk. Health officials in China say the problem has been corrected. But the situation is a reminder of the importance of milk safety measures.
Researchers at Cornell are working with American dairy farmers on new systems. Doctor Schukken sees a lot of promise in bulk-tank monitoring systems. Milk is kept cold in large tanks where it is continuously mixed. This way, any testing sample is considered a good representation of all the milk. Less than one hundred milliliters is all the milk needed for laboratory tests for bacteria, viral diseases and other threats.
And that's the VOA Special English Agriculture Report, written by Jerilyn Watson with additional reporting by Veronique LaCapra. I'm Bob Doughty.