| Polyunsaturated fatty acids (PUFA) have received a great deal of attention for their effects on the immune system. The present study showed that feeding high levels of n-3 fatty acids (5% linseed oil or fish oil) to laying hens increased longer-chain n-3 PUFA, eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in the immune cells, and consequently, decreased the estimated rate of lymphocyte proliferation and increased immunoglobulin G (IgG) concentrations in serum and egg yolk. The proportions of lymphocyte subsets were, however, unaffected. The effect of dietary n-3 PUFA on the fatty acid composition of immune tissues and the immune responses remained in the progeny if the same type of maternal and neonatal fat diets were provided. The maternal and neonatal n-3 PUFA elevated the proportion of CD8+ T-cells and IgM + B-cells, which were, however, not associated with the alterations of immune responses. Higher levels of maternal and neonatal dietary PUFA promoted the growths of thymus, spleen and bursa of the progeny before 4 wk. This effect disappeared for thymus and spleen during the period from 5 to 8 wk, while the bursa weight was lower in the groups with higher levels of n-3 PUFA, especially the fish oil group. Solely maternal dietary n-3 PUFA increased the incorporation of these fatty acids into the immune tissues of the progeny and suppressed inflammatory response until the age of 4 wk. The ratio of n-6 to n-3 PUFA plays a major role of dietary fatty acids in regulating chicken immune responses. Decreasing the ratio of dietary n-6 to n-3 PUFA suppressed chicken inflammatory response and associated with the increase of total IgG and specific antibody IgG transfer from yolk to the embryo. A significant correlation was found between the total IgG and antibody IgG in the sera of the hens, 11-d embryo, and hatching chicks. The modulating effects of dietary n-3 PUFA on chicken immune responses may be used to improve poultry health and productivity. For practical use, however, more experimentation is warranted. |
