Manipulation of the type of fat consumed by growing pigs affects plasma and mononuclear cell fatty acid compositions and lymphocyte and phagocyte functions

To investigate the immunological effect of feeding pigs different dietary l ipids, 3-wk-old, weaned pigs were fed for 40 d on one of five diets, which differed only in the type of oil present (the oil contributed 5% by weight of the diet and the total fat content of the diets was 8% by weight). The o ils used were soybean (control diet),high-oleic sunflower oil (HOSO), sunfl ower oil (SO), canola oil (CO), and fish oil (FO; rich in long-chain [n-3] polyunsaturared fatty acids). There were no significant differences in init ial or final animal weights, weight gains, or health scores among the group s. There were no significant differences in the concentration of anti-Esche richia coli vaccine antibodies in the gut lumens of pigs fed the different diets. The fatty acid composition of the diet markedly affected the fatty a cid composition of the plasma and of mononuclear cells (a mixture of lympho cytes, monocytes, and macrophages) prepared from the blood, lymph nodes, or thymus. The FO feeding resulted in a significant increase in the number of circulating granulocytes. The FO feeding significantly decreased the propo rtion of phagocytes engaged in uptake of E. coli and decreased the activity of those phagocytes that were active. The proliferation of lymphocytes in cultures of whole blood from pigs fed the HOSO, SO, or FO diets was less th an in those from pigs fed the CO diet. Proliferation of lymph node lymphocy tes from SO- or FO-fed pigs was less than that from control, CO-, or HOSO-f ed pigs. The natural killer cell activity of blood lymphocytes from pigs fe d the FO diet was significantly reduced compared with those from pigs fed t he CO diet. The concentration of PGE(2) in the medium of cultured blood, ly mph node, or thymic mononuclear cells was lower if the cells came from pigs fed the FO diet. Thus, the type of oil included in the diet of growing pig s affects the numbers and functional activities of immune cells in differen t body compartments.