Farmers scrambling to find feed that doesn't carry the risk of mad cow disease could run up against temporary shortages, a problem complicated by Europe's aversion to genetically modified crops, officials said Wednesday. 

The six-month ban adopted by the European Union this week on feeding farm animals fodder containing ground-up animal byproducts which scientists believe is the main way mad cow disease is transmitted takes effect Jan. 1. 

That applies not only to sales at feed stores but to stocks already in barns, EU commission spokeswoman Beate Gminder said. 

Authorities in each of the 15 EU states will be responsible for policing the ban, which expands a 1994 order prohibiting the use of cattle, sheep, goat and pig carcasses in cattle feed. 

The new order extends the ban to poultry and fishmeal in cattle feed, and prohibits all animal meal in feed for all other barnyard animals to prevent cross-contamination. 

Coming at the start of winter, the rules could make it hard to keep some animals properly fed, at least initially. 

"We're at a time of year where there's a lot of feeding going on," said Ian Gardiner, deputy director general of the National Farmers' Union in Britain. "The cattle and sheep aren't out in the fields." 

Producers have to clean up their plants before producing plant-based feed, and supplies have to be imported. U.S. soybean prices have already shot up in anticipation. 

"No cows are going to starve to death" because of the ban, said Otto Grote, director of the German Association of Animal Feed Producers. 

But he warned it would create distribution headaches and push up costs for farmers, and ultimately consumers, considerably. 

"The biggest problem is that it's such short notice," he said. 

Meat and bone meal make up about 14 percent of animal feed used in Europe. To replace it, EU officials expect another 3 million tons of soybeans, on top of the 30 million tons already imported each year, will be needed. 

Most of that comes from the United States, which raises another sensitive food issue in Europe genetically modified crops. 

Austrian Farm Minister Wilhelm Molterer warned last week on ORF radio that stepping up imports of biotech could "just replace one emotional debate with another." 

Some genetically altered soybeans already have EU approval and are used unnoticed in animal feed, but environmentalists are hoping the attention focused on the food industry by the mad cow crisis will aid them in their fight against such crops. 

Greenpeace activists on Sunday blocked a U.S. cargo ship trying to enter port in Ghent with a load of soybeans, charging they were biotech crops. 

"Just remember that for many years the scientific panels said there was no evidence of the risk that mad cow disease could pass to humans ... but it did," said Lorenzo Consoli, media officer for Greenpeace International in Brussels. 

"Now they say there's no evidence that genetically engineered crops are harmful. I would give that the same weight." 

His organization is pushing the EU to enact legislation that would at least require feed with biotech contents to be labeled as well as the meat coming from any animals that ate it. 

That, however, would take years to implement. Getting Europeans to grow more protein crops, such as peas and beans, would also take time. 

In the meantime, supplies of non-altered soybeans from other growers, such as Brazil, are "not enough by far," Grote said. 

German Agriculture Minister Karl-Heinz Funke complained Wednesday that enacting only a six-month ban, with uncertain prospects after that, won't encourage European farmers to invest in such crops. 

EU Farm Commissioner Franz Fischler sees another problem. 

"Unfortunately, in order to be independent from soya imports, we would have to change the climate, because soya barely grows in Europe," he said this week in Paris.