Fish oil and other nutritional supplements added to swine diets could help boost immunity in piglets and could replace growth-promoting antibiotics traditionally given to the young animals, according to Agricultural Research Service scientists.

Many countries are phasing out antibiotics in animal feed because antibiotics are expensive and because animals are developing resistance to them.

Jeff Carroll, research leader of the ARS Livestock Issues Research Unit, Lubbock, Texas, and his colleagues are testing spray-dried plasma, fish oil and other nutritional supplements to find alternatives to antibiotics.

Antibiotics have been used to help piglets as they are weaned. Piglets are usually weaned at 18 to 21 days, but sometimes as early as 10 days. This can leave them vulnerable to diseases because their immune systems are not yet fully developed. ARS researchers are investigating diets that not only help boost the immune system, but also maintain growth rates acceptable to swine producers.

Spray-dried plasma, a byproduct of the meat-packing industry, is often used to enhance growth and feed efficiency. The plasma protein is fed to piglets for the first few weeks after weaning, starting at a 5- to 7-percent ration and reduced gradually to 2.5- to 3.5-percent as their immune systems become more mature. According to Carroll, plasma may increase immunity in piglets by preventing pathogens from binding to the intestines.

To enhance immunity further, a 7-percent mixture of menhaden fish oil is incorporated into the piglet diet rations. Menhaden oil contains high levels of omega-3 fatty acids, which help build immunity in the animals' cells, according to Carroll.

Read more about the research in the July 2005 issue of Agricultural Research magazine, available online at: http://www.ars.usda.gov/is/AR/archive/jul05/pigs0705.htm