Soon you won't have to wait till the cows come home.

New systems for robotic milking, automated sanitation and computer-controlled milk-handling mean that today's dairy farmers can sleep in, and let the cows come home when they want to.

For the modern dairy farmer, this means no more 4 a.m. herding of recalcitrant cows, no repeats of the process in late afternoon, and probably more milk. Because the cows wander in on their own, when ready for milking, they tend to give more moo juice.

According to a report in Mechanical Engineering magazine, the Royal Institute of Technology in Stockholm, Sweden, concludes that cows milked voluntarily can be milked more often, increasing production. There is also rising demand for self-cleaning, automated milking systems that ensure bacteria-tainted milk does not contaminate the milk in big tanks.

DeLaval International AB, in Tumba, Sweden, developed the milking system based on computer-controlled robotic arms devised by Norgren AB, of Malmo, Sweden.

Norgren's product manager, Ken Olsson, told the magazine that "cows that are milked only twice a day will not produce as much as those milked more often." He said the animals that are ready for milking during the night, if forced to wait until morning, feel pressure buildup in their udders, are uncomfortable and stop making milk.

But "with the voluntary milking system, she can be milked any time she is ready, and the farmer doesn't even have to wake from his sleep," Olsson said.

Each cow wears an identity tag, and the tag is scanned automatically when it comes to the milking station, where food is supplied as enticement. The computer keeps track of each cow's visit, records how much milk is given and monitors timing to ensure the cow is actually ready to be milked. If all the signs are right, a gate opens automatically and bossy is allowed into the milking stall. Data about each cow allow the robot arms to fit the milking machine properly, making sure the cow is comfortable.

As the milk begins flowing -- without any aid from human hands -- computerized systems are monitoring the fluid itself, checking for bacteria or other contaminants. If a problem is seen, the flow of milk is shunted off to special tanks, so it does not reach the main supply and contaminate larger amounts of milk.

Once the milking process ends, the voluntary milking system carefully cleans the cow's teats and udder. Then the system cleans all its own parts, setting itself up for arrival of the next milk-laden cow.

Olsson added that although the voluntary milking system is still being perfected, it is already being widely used in European nations such as Sweden, Denmark, Poland and Germany, as well as in Japan.

Researchers at the University of Wisconsin Center for Dairy Research note there is increasing pressure in the United States for development of such self-cleaning robotic milking systems.