To investigate the effects of acute cold stress (ACS) on chicken heart after cold stimulation, female broilers were raised in either normal (C) or gradually decreasing temperatures (CS I and CS II) for 34 days followed by a 24 h ACS at 7°C. Cardiac tissues were collected from the pre-ACS and ACS time points to analyze the histopathological changes, antioxidant status and the expression of heat shock proteins, inflammatory factors and immune-related cytokines. The CS II heart tissues showed shrunken cell membranes and nuclei, disordered or ruptured myocardial fibers, higher MDA content and upregulation in HSP27, HSP40, HSP70, NF-κB, COX-2, PTGEs, iNOS, TNF-α and IL-4 mRNAs, and in protein levels of HSP40, NF-κB and iNOS and reduction in CAT, GSH-px and SOD activity, as well as HSP90 and IFN-γ levels compared to the control tissues before ACS. In contrast, the HSPs were significantly increased, and the inflammatory and immune related factors were unaltered prior to the ACS in the CS I compared to the C group. Following ACS, MDA content was significantly increased and antioxidant activity was significantly decreased in the CS I and CS II groups compared to the C group. The levels of HSP27, HSP70, HSP90, inflammatory factors and IL-4 were significantly reduced and that of IFN-γ was significantly increased in CS I broiler hearts; the reverse trends were seen in CS II relative to CS I. Compared to the pre-ACS levels, that of HSP27, HSP40, HSP60, inflammatory factors and IL-4 were increased and IFN-γ was decreased in the C and CS II groups after ACS. Therefore, cold stimulation at drastically lower temperatures induced cardiac damage, which was further aggravated by ACS. In contrast, cold stimulation at only 3°C lower than normal temperature improved the adaptability of the broilers to ACS.

Acclimation can alleviate the damage caused by adverse environmental factors. To investigate the effects of cold stimulation on immunity in tracheal of broilers, 360 one-day-old chicks were raised at normal temperatures during 1-7 days. From 8 day, G1 (control) continued to be raised at normal temperatures, whereas G2 and G3 (treatment groups) were cold-stimulated at 3°C and 12°C below the temperature of G1, respectively. At 42 day, all the groups were subjected to a 24-hr acute cold stress, designated as S1, S2, and S3. Tracheal tissues were collected to detect gene levels of immunoglobulins, antimicrobial peptides, Hsps, and cytokines, and oxidative stressrelated indicators at 14 day, 42 day, and 43 day, and protein levels of Hsps and proinflammatory cytokines as well as morphology changes at 42 day and 43 day. The results showed that, compared with 42G1, tracheal structure of 42G2 was basically intact, and gene levels of immunoglobulins and antimicrobial peptides increased (p < 0.05), whereas tracheal structure of 42G3 was destroyed, with decreased levels of immunoglobulins (p < 0.05), and increased levels of Hsps and proinflammatory cytokines (p < 0.05). At 43 day, tracheal damage was visible and gene levels of immunoglobulins and antimicrobial peptides decreased in S1 (p < 0.05). Tracheal structure was relatively intact and gene levels of antimicrobial peptides increased in S2 (p < 0.05). Compared with S1 and S3, immune-related gene levels in S2 were higher, and Hsps and proinflammatory cytokines levels were lower. The results demonstrate that cold stimulation of lower 3°C from 8 to 42 day led to cold acclimation, which improved immunity of tracheal mucosa and resistance to cold stress in broilers.

This experiment aimed to evaluate the effects of different housing systems on behavioral activities, welfare and meat quality of fast-growing broilers. Two hundred broilers were allocated into two housing systems: indoor housing vs indoor with outdoor access. Their general behavior (feeding, drinking, fighting, standing, lying, walking, investigating, dust-bathing and preening) was observed, and tonic immobility, fluctuating asymmetry of legs and wings were measured, and meat quality was analyzed. The results showed that the indoor-housed broilers with outdoor access had significant higher standing, walking, investigating, dust-bathing and preening than those indoor only. However, farming system was not found to significantly affect their feeding, drinking and fighting activities (p>0.05). The value of FA of tibia length of the broilers with outdoor access was significantly lower than that of the indoor-housed birds (1.57±1.30 vs 2.76±1.40, p<0.05), while no difference was found for the value of FA in tibia diameter and wing length (p>0.05). TI of the broilers with outdoor access was 165.5 that was significantly higher than that (147.2) of the indoor birds (p<0.05). However, death rate in the outdoor run groups was significantly higher than that of the indoor ones (2.0±0.81 vs 4.0±0.82, p<0.05). Meat quality was not affected by the two farming systems. It can be concluded that the results of this study may suggest that the indoor housing with outdoor access provides enriched environment for broilers and facilitates the expression of natural behaviors of the broilers but resulted in poorer performance and higher death rate.

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