Performance and immune responses to dietary beta-glucan in broiler chicks.
During the first week posthatch, the avian immune system is immature and inefficient at protecting chicks from invading pathogens. Among immunomodulators, beta-glucans are known as biological response modifiers due to their ability to activate the immune system. Current research suggests that beta-glucans may enhance avian immunity; however, very little is known about their influence on regulation of immune function. A study was performed to evaluate the effects of dietary beta-glucan on growth performance, immune organ weights, peripheral blood cell profiles, and immune-related gene expression in the intestine. One-day-old chicks were fed a diet containing 0, 0.02, or 0.1% yeast beta-glucan (n = 30/treatment). On d 7 and 14 posthatch, body and relative immune organ weights were measured and small intestinal sections were collected to evaluate gene expression by quantitative real-time PCR. Peripheral blood samples were also collected to determine heterophil:lymphocyte ratios. Supplementation of beta-glucan did not significantly affect BW gains, and no significant differences were observed among groups for relative immune organ weights or heterophil:lymphocyte ratios. Compared with controls, expression of interleukin (IL)-8 was downregulated in the beta-glucan-treated groups on d 7 and 14. On d 14, beta-glucan inclusion resulted in increased inducible nitric oxide synthase expression. Expression of IL-18 was upregulated on d 7 but reduced on d 14 due to beta-glucan supplementation. On d 7, interferon-gamma and IL-4 expression decreased in the beta-glucan-treated groups. However, on d 14, IL-4 expression was upregulated in the supplemented groups. Intestinal expression of IL-13 was also downregulated in the beta-glucan-treated birds on d 7. These results suggest that dietary inclusion of beta-glucans altered the cytokine-chemokine balance; however, it did not elicit a robust immune response in the absence of a challenge, resulting in no deleterious effects on performance.
Cox
C M
CM
Avian Immunobiology Laboratory, Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, USA.
Stuard
L H
LH
Kim
S
S
McElroy
A P
AP
Bedford
M R
MR
Dalloul
R A
RA
D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001772:Blood Cell Count; D002645:Chickens / Q000254:growth & development*; D004032:Diet / Q000662:veterinary*; D005786:Gene Expression Regulation / Q000187:drug effects; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D015430:Weight Gain / Q000187:drug effects*; D047071:beta-Glucans / Q000494:pharmacology*
D016209:Interleukin-8; D047071:beta-Glucans