Two experiments were designed to determine the effects of dietary (n-3)
fatty acids and grain source on the growth-suppressive effects of the inflammatory response and indices of specific immunity. In Experiment 1, chicks were fed diets containing 0.5, 1, or 2 g/100 g of either
corn oil or
fish oil. In Experiment 2, chicks were fed diets containing up to 2 g/100 g of either
fish oil,
linseed oil or
corn oil as the source of
dietary fat, in either cereal grain- or corn-based diets. In each experiment, subsets of chicks within each dietary treatment were either vaccinated with infectious bronchitis virus (IBV)
vaccine, injected with Salmonella typhimurium
lipopolysaccharide (LPS), heat-killed Staphylococcus aureus, or remained noninjected. Increasing dietary
fish oil, but not
corn oil increased
body weight and lessened the growth-suppressing effect of heat-killed S. aureus or S. typhimurium LPS. Increasing the concentration of dietary
fish oil decreased febrile response, circulating
hemopexin and
metallothionein concentrations. Dietary
fish oil resulted in decreased release relative to dietary
corn oil of
interleukin-1 by peritoneal macrophages. Although IBV titers were not significantly affected by
dietary oil treatment, phytohemagglutination-induced wattle swelling was greater among chicks fed
fish oil. In Experiment 2, the modulating effects of
fish oil on the immune system were dependent on the type of grain used in the diet, with
fish oil/cereal diets resulting in greater cell-mediated immunity and lower indices of
inflammation than
fish oil/corn diets. Inclusion of increasing amounts of
fish oil in the diet improved performance, decreased indices of the inflammatory response and either improved or did not change indices of the specific immune response of growing chicks.