POULTRY farmers can stop dosing their birds with antibiotics. Researchers in Wisconsin have developed an alternative to the controversial practice of adding antibiotics to feed to make poultry grow quickly: adding antibodies against appetite-suppressing neurotransmitters and a fatty acid first isolated from hamburgers.
Antibiotics work as growth promoters because, by knocking out bacteria, they help prevent stimulation of the immune system. When a bird鈥檚 immune system is stimulated by infection, immune cells release chemical messengers such as interleukin-1 or tumour necrosis factor. These cause muscle wasting and also cause the release of peptide neurotransmitters that suppress appetite. 鈥淐hickens respond to immune stimulants much the way we do to flu,鈥� says Mark Cook of the University of Wisconsin in Madison. 鈥淭hey don鈥檛 want to eat, their muscles begin to break down and they lose weight.鈥�
But the wholesale use of antibiotics could have serious consequences. The European Union has already banned the use of five antibiotics as growth promoters, fearing that they could encourage the spread of resistance to drugs used against dangerous human pathogens.
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Cook鈥檚 approach is based on antibodies that block the actions of the appetite-suppressing neurotransmitter peptides, which are produced in the gut. To make the antibodies, they inject chickens with small fragments of the peptides attached to larger carrier molecules. The birds secrete antibodies against the neurotransmitters, which are incorporated into the yolks of their eggs. DCV of Wilmington, Delaware has developed a way of harvesting the yolk without denaturing the antibodies. The yolk is then powdered and added to chicken feed in small quantities.
The antibody supplements produce growth gains similar to those given by antibiotics. 鈥淲e鈥檙e getting a 3 to 5 per cent improvement in growth,鈥� says Cook.
His team is also working on another feed additive, called conjugated linoleic acid (CLA). This fatty acid is produced by bacteria that live in the guts of ruminants, such as cows and sheep. It is found in ground beef and is thought to have anticancer properties. CLA also increases growth rates in chickens, by blocking the chemical messengers that cause muscle wasting.
DCV is preparing to launch the antibody additive, called Ovation, in the US and will be conducting European trials early this year. Meanwhile, Conlinco of Detroit Lakes, Minnesota, is planning to market CLA supplements.