Immune response and blood chemistry of pigs fed conjugated linoleic acid

Immune function (response to concanavalin A, cytokine production, and lymphocyte profiles) and blood chemistry variables were measured in growing-finishing pigs (Yorkshire/Landrace/Duroc dam × Hampshire sire) fed varying percentages of CLA (0, 0.12, 0.25, 0.50, and 1.0%). Blood was collected at 0, 14, 28, 42, and 56 d on feed (DOF). Total white blood cell (WBC) count increased (P < 0.01) linearly to 42 DOF. No differences (P = 0.53) were observed for WBC across CLA treatment. Nitric oxide was greater (P < 0.01) for the 1.0% CLA treatment compared with all other treatments. Flow cytometry using fluorescent labeled monoclonal antibodies to the CD4, CD8, double-positive CD4/CD8, and CD2 surface markers was used to determine lymphocyte subpopulations. Supplementation of CLA had no effect (P = 0.61) on lymphocyte subpopulation cell distribution. Most blood chemistry variables were within the normal metabolic range for pigs. A decrease was observed over DOF for P (P < 0.01) and K (P < 0.05). Additionally, Na and Cl concentrations increased (P < 0.05) from 14 to 28 DOF and decreased over the remainder of the trial. Electrolyte balance was not different (P = 0.38) across CLA treatments and was likely explained by no differences in feed intake among the CLA treatment groups. Blood lipid variables indicated that total cholesterol (P < 0.001), triglycerides (P < 0.001), high-density lipoproteins (P < 0.001), and low-density lipoproteins (P < 0.01) increased as the amount of CLA in the diet increased, but none of the results from these treatments exceeded the normal range of acceptability. These results suggested that CLA was safe when fed to growing-finishing pigs and had little effect on their immune function and blood chemistry variables.