An experiment was conducted to evaluate
the effect of CLA on the immune response and
performance of piglets when subjected to an immune
challenge. A total of 32 weanling pigs (17 to 23 d of
age) with an initial BW of 8.9 kg were allotted to a 3
× 2 factorial arrangement of treatments. There were 3
levels of dietary CLA (0%, 1%, and 2%) and 2 levels of
lipopolysaccharide (LPS) challenge (unchallenged and
challenged). Challenged pigs were challenged on d 7
and 21. On d 4 and 18, all pigs were inoculated with BSA
for assessment of IgG production. There was no difference
in growth performance among piglets receiving
different CLA supplementation levels. However, LPSchallenged
piglets had poorer BW (P < 0.05), ADFI
(P < 0.01), and ADG (P < 0.001) compared with the
control group at d 35 postweaning. Lipopolysaccharidechallenged
piglets also had increased respiratory rate
(P < 0.001) and rectal temperature (P < 0.001), and
decreased plasma proteins, hematocrit, and white blood
cell counts (P < 0.05). Production of IgG against BSA
was increased in the 1% CLA supplementation group
(P < 0.001), indicating that CLA has an immunomodulatory
effect. Supplementation with CLA did not
affect lymphocyte proliferation, percentage of CD4+
and CD8+ cells, plasma proteins, red and white blood
cell count, respiratory rate, or rectal temperature after
LPS challenge. Although CLA supplementation did not
infl uence growth performance or certain immune system
measurements, the increased IgG titers with 1%
CLA dietary supplementation indicate that it has a benefi
cial effect on the humoral immune system of weaned
piglets