Buildings, trains, ships and, now, the U.S. food supply are all potential targets that the U.S. government is trying to protect from a possible terrorist attack.

Ever since plans to attack American agriculture were found in the caves of Afghanistan, Homeland Security (search) has been planning for an assault on the nation's meat and milk supply or an attempt to contaminate the seeds used to grow vegetables.

Please click on the video box on the right to watch a full report by FOX News' Dan Springer.

"In the unlikely, but possible event of some kind of activity, some kind of contamination being in the food supply, we're gonna catch it," said Charles Conner, the deputy secretary for the U.S.D.A. (search). "We're gonna contain it and we're going to protect our consumers."

The government has spent $1 billion training FBI agents, educating farmers and creating a network of regional labs — where blood samples from livestock that die mysteriously can be quickly tested for signs of intentional poisoning.

Leonard Eldridge, a Washington State veterinarian, said, "My goal is a 48-hour response to anything a practitioner might call for."

Cows are the No. 1 agricultural concern for officials. By launching a bio-weapon (search) in the air, an entire herd could easily be poisoned, they fear. As cattle are trucked around the country from farm to farm, the infection could quickly spread.

In the case of agricultural contamination, it's up to the farmers to be the nation's first line of defense to contain it. And many farmers say they're more concerned about animal rights activists than Al Qaeda. Jason Bartelheimer, a dairy farmer, said, "It's something to think about, but then again, how much time and effort do you spend on that when it hasn't happened yet? You just can't make everything foolproof."

The health impact isn't the only thing worrying officials: Tainted food could close foreign markets to our $59 billion export industry, costing millions of Americans their dinners and their jobs.