The innovation comes as growing public concern about antibiotic resistance has induced McDonald's, Tyson Foods and other industry giants to announce major cuts in antibiotic use in meat production.

About 80 per cent of antibiotics in the United States are used by farmers, because they both protect against disease and accelerate weight gain in many farm animals, but recently announced regulations will put an end to the use of antibiotics for production purposes by the end of 2016.

The overuse of antibiotics in agriculture and medicine has created a public health crisis of drug-resistant infections, such as multidrug resistant staphylococcus aureus (MRSA) and "flesh-eating bacteria."

"You really can't control the bugs forever; they will always evolve a way to defeat your drugs," said Mark Cook, a professor of animal sciences at the University of Wisconsin-Madison and an entrepreneur.

Mr Cook's current work focuses on a fundamental immune "off-switch" called Interleukin 10 or IL-10, manipulated by bacteria and many other pathogens to defeat the immune system during infection.

He and animal sciences associate researcher Jordan Sand have learned to disable this switch inside the intestine, the site of major farm animal infections such as the diarrheal disease coccidiosis.

Mr Cook vaccinates laying hens to create antibodies to IL-10. The hens put the antibody in eggs, that are then sprayed on the feed of the animals he wants to protect. The antibody neutralises the IL-10 off-switch in those animals, allowing their immune systems to better fight disease.

In experiments with 300,000 chickens, those that ate the antibody-bearing material were fully protected against coccidiosis.

"These diseases cause long-term reproduction, production and growth impairments in livestock," said Sheila McGuirk, a professor of medical sciences at the School of Veterinary Medicine.

"The affected animals are suboptimal in health, performance and profitability. To have something affordable, safe and nonantibiotic that controls these very important diseases is absolutely awesome. We are eager to study this further."

In the past few years, scientists have learned that a large group of pathogens - including bacteria, single- and multicelled parasites, protozoa, even certain viruses - make a chemical called macrophage migratory inhibition factor, or MIF, which activates the IL-10 mechanism to shut down the host animal's immune system.

"This apparently arose deep in the evolutionary past, and it's wholesale piracy of the immune system," said Mr Sand.

Mr Cook and Mr Sand, who have been working on the IL-10 system since 2011, are forming Ab E Discovery LLC to commercialise their research. One of the four patents they have filed through the Wisconsin Alumni Research Foundation has just been granted, and WARF has awarded a $100,000 Accelerator Program grant to the inventors to pursue the antibiotic-replacement technology.

The benefits of reducing farm usage of antibiotics should extend to workers' families and the wider population. Significantly more people working in conventional chicken farms carry multidrug-resistant pathogens than those who work in antibiotic-free farms, Mr Sand noted.

A nonantibiotic method to prevent pathogens from shutting down the immune system seems far less conducive to resistance than the current routine feeding of antibiotics, Mr Cook said.