Changes in performance, blood parameters, humoral and cellular immune responses in weanling piglets exposed to low doses of aflatoxin.

A feeding trial was conducted to evaluate the effect of aflatoxin (AF)-contaminated diets on growth and hematological and immunological parameters. Low doses of aflatoxins (140 and 280 ppb) were included in a corn-soybean diet provided for ad libitum consumption to 36 weanling piglets for a period of 4 wk. A "dose-related" decrease in weight gain was observed in treated animals. This effect was significant (P < 0.05) in the 280 ppb-treated group compared to the control group. Ingestion of AF-contaminated feed at either level had no effect on total red blood cell numbers or on their relative number of lymphocytes, monocytes, neutrophils, basophils, and eosinophils in blood. Likewise, AF did not alter globulin, albumins, or total protein concentrations in serum, nor did AF alter the expression of regulatory cytokines produced by either Th1 (IL-2) or Th2 (IL-4) lymphocyte subsets in phytohemagglutinin-stimulated blood samples. By contrast, AF had a biphasic effect on total white blood cell number; the low dose of AF (140 ppb) decreased the total number of white blood cells, whereas the high dose (280 ppb) had the opposite effect. Consumption of AF also increased the concentration of gamma-globulin in the serum. A reduced immune response induced by Mycoplasma agalactiae in the 280-ppb-treated group was also observed. Cytokine mRNA expression in phytohemagglutinin-stimulated blood cells indicated that AF decreased proinflammatory (IL-1beta, TNF-alpha) and increased anti-inflammatory (IL-10) cytokine mRNA expression. These results demonstrate that low doses of AF depress growth and alter many aspects of humoral and cellular immunity in pigs.