Effects of prior cold stimulation on inflammatory and immune regulation in ileum of cold-stressed broilers

Acclimation can alleviate the negative impacts of adverse environmental factors on an organism. To investigate the effects of prior cold stimulation on inflammatory and immune regulation in ileum of cold-stressed broilers, 360 1-d-old chicks (Arbor Acres) were divided into 3 groups (G1, G2, G3) and raised at normal (thermal comfort) temperatures during 1 to 7 d. From 8 d, G1 (control) continued to be raised at normal temperatures, whereas G2 and G3 (treatments) were cold-stimulated at 3°C and 12°C, respectively, below the temperature of G1, but not below 17°C (reached at 32 d in G2 and 14 d in G3). At 42 d, all the groups were subjected to a 24-h acute cold stress of 7°C, designated as S1, S2, and S3. Ileum tissues and serum of the birds were collected at 42 d and 43 d to detect the levels of pro-inflammatory and immune-related factors as well as morphology changes. At 42 d, ileum of G1 and G2 had intact morphological structure and clear outline, with no differences in levels of iNOS, NF-κB, COX-2, PTGEs, TNF-α, IFN-γ, or IL-4 (P > 0.05). G3 ileum suffered inflammatory injuries, with levels of iNOS, COX-2, PTGEs, TNF-α, and IL-4 being higher than those of G1 (P < 0.05). At 43 d, compared with G1, S1 had severely damaged ileum, increased levels of iNOS, NF-κB, COX-2, PTGEs, TNF-α, and IL-4 (P < 0.05), but decreased level of IFN-γ (P < 0.05). The morphological structure of S2 was intact, and there were no differences between G2 and S2 in levels of NF-κB, PTGEs, TNF-α, IFN-γ, or IL-4 (P > 0.05). Compared with S1, S2 had decreased levels of iNOS, NF-κB, COX-2, PTGEs, TNF-α, and IL-4 (P < 0.05), but increased level of IFN-γ (P < 0.05). There were no differences between G1 and S2 in levels of NF-κB, PTGEs, TNF-α, IFN-γ, or IL-4 (P > 0.05). The results demonstrate that a 3°C-lower-than-normal temperature stimulation of the broilers from 8 to 42 d led to cold acclimation. This prior cold acclimation effectively alleviated elevation of pro-inflammatory cytokines and Th1/Th2 imbalance of the birds induced by subsequent cold stress.