The effect of methionine and aflatoxin on immune function in weanling pigs

To investigate the effect of aflatoxin (AF) and dietary methionine (MET) on immune responses of swine, a total of 288 pigs weaned at 21 d of age were allotted to 12 dietary treatments arranged in a 3 x 4 factorial arrangement in a randomized complete block design. Diets consisted of a corn-soybean meal diet (.95% lysine, .30% MET, and .32% cystine) containing either 0, 140, or 280 ppb of AF and supplemented with either 0, .15, .30, or .45% DL-MET. Immune response measurements were made after the pigs had received their diet for 3 wk. Antibody response to sheep red blood cells (SRBC) was measured 0, 7, and 14 d after i.m. injection of 2.5 mL of a 20% SRBC suspension. Total serum immunoglobulin (Ig) M and IgG were measured using an ELISA. In vivo cellular immunity was measured using a phytohemagglutinin (PHA) skin test. Skin thickness was measured 0, 6, 12, 24, and 36 h after s.c. injection of .1 mL of PHA (1.50 mg/mL). In vitro cellular immunity was measured using a lymphocyte blastogenesis assay. Antibody response to SRBC and serum IgM and IgG concentrations were not affected by dietary treatments. Skin thickness response at 6 h after injection was maximal when .45% MET was added to diets containing 280 ppb of AF, whereas the response was maximal at .30% supplemental MET for the 0 and 140 ppb of AF diets (AF x MET interaction, P < .10). Skin thickness was reduced linearly (P < .10) with increasing dietary AF at 12 and 24 h after PHA injection.(ABSTRACT TRUNCATED AT 250 WORDS)