The ruling stems from a lawsuit brought last year by a coalition of consumer of advocacy groups suing the FDA over its inaction in addressing the growing public health threat posed by the daily dosing of antibiotics in livestock feed and the rise of antibiotic-resistant bacteria.

The lawsuit came on the heels of an FDA report released to Congresswoman Louise Slaughter confirming that 80 per cent of antibiotics are sold for use in agriculture.

"It's about time," said Congresswoman Slaughter.

"The FDA has been dragging its feet on this for 35 years.

"We've all known that this is a public health issue for quite some time. Of course if an animal is sick, it should be treated. But the evidence for ending the daily dosing of antibiotics to otherwise healthy animals is overwhelming.

"I'm pleased to finally see some progress and I can only hope that we see swift action from the FDA on this looming crisis."

In 1977 the FDA proposed withdrawing approval for penicillin and tetracyclines from livestock feed, recognising the danger posed to public health. Since then, the FDA has taken no action to limit its use.

The ruling made on Thursday 22 March last week forces the FDA to withdraw approval for the two classes of antibiotics.

Since 2007, Congresswoman Slaughter has been the author of legislation titled The Preservation of Antibiotics for Medical Treatment Act (PAMTA), designed to ensure that we preserve the effectiveness of antibiotics for the treatment of human disease.

The legislation would prevent the overuse of seven classes of antibiotics, including penicillin and tetracyclines.

"We still have a lot of work to do here," said Congreswoman Slaughter.

"This is a good first step but to really get in front of this problem we must address all classes of antibiotics in farm animals that are important to human health. That's why I will continue to press for passage of PAMTA."

In its decision, the court noted: "Research has shown that the use of antibiotics in livestock leads to the development of antibiotic-resistant bacteria that can be - and has been - transferred from animals to humans through direct contact, environmental exposure, and the consumption and handling of contaminated meat and poultry products."