The antibiotic-free technology involves extracting antibodies in egg yolks from pathogen-free hens that have been hyperimmunised – injected with a vaccine that contains inactivated pathogenic organisms.
Hyperimmunised birds have a greater-than-normal immunity and produce a large amount of antibodies.
A United States Agricultural Research Service (ARS) team showed the effectiveness of inducing passive immunity in young birds which normally have no immune protection against coccidiosis immediately after hatching.
Birds affected by coccidiosis are unable to absorb feed or gain weight. The disease costs the global poultry industry about US$3 billion/year.
A commercial product that helps control coccidiosis has been developed by a private company based on results of the research and the ARS scientists say similar methods may be able to be used to help prevent other harmful poultry diseases.
Avian immunologist Hyun Lillehoj at the ARS Animal Parasitic Diseases Laboratory in Beltsville, Maryland, says antibiotic-free alternatives are important to help fight drug-resistant strains of diseases and for organic poultry farmers.
“Coccidiosis is associated with other pathogens, such as the one that causes necrotic enteritis – a prevalent gut disease of poultry. By controlling one, you’re also reducing the impact of the other,” says Lillehoj.
Generally, a host can develop two types of immunity to resist infection: active and passive. Passive is when already formed antibodies are transferred from the hen, via the yolk, to the chick. Active immunity relies on vaccines or natural exposure to build immunity in the birds.
“When chicks hatch, they have no immunity to this [coccidiosis-causing] pathogen.
“But if we give preformed immune proteins to one-day-old progeny, they are ready to fight infection. It’s similar to how immunity is passed to newborns through milk.”
In the study, day-old chickens were given feed mixed with spray-dried egg yolk powder prepared from hens hyperimmunised with multiple species of the parasite Eimeria, which causes coccidiosis.
The chickens were then exposed to live coccidia parasites.
Chickens that had received the hyperimmune egg yolk antibodies gained more weight and shed significantly fewer Eimeria in their faeces. The treated birds also had less gut lesions than chickens that did not receive the treatment.
“It’s very simple technology, and it works,” says Lillehoj.
