Microbiologist Irene Wesley of the ARS National Animal Disease Center (NADC) in Ames, Iowa, found that supplementing turkeys' diets with the vitamin stimulates their immune responses, helping them clear the gut of the micro-organism that causes the disease. This can in turn lead to reduced contamination of carcasses at slaughter and during processing.
Wesley is part of NADC's Pre-Harvest Food Safety and Enteric Diseases Research Unit.
Listeria monocytogenes causes listeriosis, a disease that affects mainly pregnant women, newborns, and adults with weakened immune systems. It accounts for 2,500 total cases annually of human meningitis, encephalitis, sepsis, foetal death and premature births. In a 1998 USDA study, L. monocytogenes was found in nearly 6 per cent of turkey carcass rinses and in 31 per cent of the ground turkey meat examined.
These studies, conducted in collaboration with the University of Arkansas and Iowa State University, found that vitamin E boosts turkeys' white blood cells, which go into action when disease-causing organisms are detected.
Turkeys require vitamin E for normal development and function of the immune system. Wesley used alpha-tocopherol - the most active form of vitamin E in humans, and a powerful biological antioxidant - because it is readily available from commercial sources and can be used in animal feed preparations.
Earlier tests conducted at Iowa State showed that dietary vitamin E also enhances poultry meat's quality and shelf life. Plans are in the works for testing vitamin E against Salmonella and Campylobacter, two other important foodborne pathogens.
ARS is the chief scientific research agency of the US Department of Agriculture (USDA).