The new law, which was introduced in December 2014, was passed by both the Californian Senate and Assembly last month.

It is now awaiting the final signature of the state governor Jerry Brown before passing into law.

The law, "SB-27 Livestock: Use of Antimicrobial Drugs", which is expected to come into force in January 2018, will prohibit the administration of medically important antimicrobial drugs to livestock unless ordered by a licensed vet through a prescription or veterinary feed directive.

It will also prohibit the administration of a medically important antimicrobial drug to livestock solely for purposes of promoting weight gain or improving feed efficiency.

The law requires the Department of Food and Agriculture, in consultation with the Veterinary Medical Board, the State Department of Public Health, universities and cooperative extensions, to develop antimicrobial stewardship guidelines and best management practices on the proper use of medically important antimicrobial drugs and also requires the department to gather information on medically important antimicrobial drug sales and usage, antimicrobial resistant bacteria, and livestock management practice data.

A penalty for a first breech of the law could see a fine of $250 for each day a violation occurs. Second and subsequent violations will be subject to a fine of $500 every day.

The new legislation will make California the first state in the US to restrict the use of antibiotics for farm animals and the move could have further repercussions for legislation and livestock management in other states and across the US.

Senator Jerry Hill, in introducing the bill said: “The overuse and misuse of antibiotics, especially antibiotics important in human medicine, contributes to antibiotic resistance as a growing public health threat.

“Inappropriate antibiotic use and overuse in humans drives the development of antibiotic resistance, but there is also a concern about antibiotic use in livestock and poultry.

“Based on the best information available from the federal Food and Drug Administration (FDA), it's estimated that at least 70 per cent of all medically important antibiotics are sold for use in livestock and poultry.

“Antibiotic stewardship programmes are a commitment to always use antibiotics only when they are necessary, to choose the right antibiotics and to administer them in the right way in every case.

“Antibiotic stewardship programmes have been effective in reducing inappropriate antibiotic use in humans, as well in reducing antibiotic resistance.

“However, there is no similar requirement that veterinarians and livestock and poultry producers follow antibiotic stewardship guidelines."

The original bill was drawn up by Sen. Hill together with California’s farming and agriculture organisations, veterinary associations, environmental and public health organisations, and the Governor.

However, when the bill was first introduced there was opposition from several organisations who said the bill did not go far enough.

The Consumers Union of the US together with other organisations had concerns over the preventative use of antimicrobial drugs, as well as the concern that "the data reporting part of the bill does not require reporting of total quantity of antibiotics used.”

Long-time campaigner against the use of antibiotics in livestock production, Congresswoman Louise Slaughter wrote to Gov. Brown saying: “I write to express my utmost support for a bill recently passed by the California Legislature, SB 27 Livestock: Use of Antimicrobial Drugs.

“This bill will make real change in agricultural antibiotic use and curb the growth in antibiotic resistance that threatens the health of our country.”

She added: “It seems that the best chance for change will come from the states, and I am so proud that California has taken up this fight.”