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Intermittent cold stimulation (ICS) enhances broilers' resistance to cold stress. Nonetheless, further research is needed to investigate the underlying mechanisms that enhance cold stress resistance. A total of 160 one-day-old male Ross 308 broilers were randomly divided into 2 groups (CC and CS5), with the CC group managing temperature according to the standard for broiler growth stages, while the CS5 group were subjected to cold stimulation at a temperature 3℃ lower than the CC group for 5 h, every 2 d from 15 to 35 d. Sampling was conducted at 36 d (36D), 50 d (50D) and after acute cold stress for 24 h (Y24). First, we examined the effects of ICS on broiler growth performance, meat quality, antioxidant capacity, and lipid metabolism. The results demonstrated that ICS enhanced the performance of broilers to a certain degree. Specifically, the average weight gain in the CS5 group was significantly higher than that of the CC group, and the feed conversion ratio significantly decreased compared to CC at 4 W and 6 W (P ≤ 0.05). Compared with the CC group, cold stimulation significantly reduced drip loss, shearing force, and yellowness (a* value) of chicken meat, while significantly increased redness (b* value) (P ≤ 0.05). At Y24, the levels of T-AOC and GSH-PX in the serum of the CS5 group were significantly higher than those of the CC group, while the level of MDA was significantly lower (P ≤ 0.05). The content of TG, FFA, and VLDL in the serum of the CS5 group was significantly elevated, whereas the level of TC and HDL was significantly lower (P ≤ 0.05). In addition, we further explored whether AMPK-mTOR pathway is involved in the regulation of changes in lipid metabolism and the possible regulatory mechanisms downstream of the signaling pathway. The results showed that ICS significantly upregulated the expression levels of AMPK mRNA and protein in the liver of the CS5 group at 36D and Y24, while significantly down-regulating mTOR (P ≤ 0.05). Compared with the CC group, ICS significantly down-regulated the mRNA expression levels of lipid synthesis and endoplasmic reticulum stress-related genes (SREBP1c, FAS, SCD, ACC, GRP78 and PERK) at 36D and Y24, while significantly up-regulating the mRNA expression levels of lipid decomposition and autophagy-related genes (PPAR and LC3) (P ≤ 0.05). In addition, at Y24, the protein expression levels of endoplasmic reticulum stress-related genes (GRP78) in the CS5 group were significantly lower, while autophagy-related genes (LC3 and ATG7) were significantly higher (P ≤ 0.05). ICS can affect meat quality and lipid metabolism in broilers, and when broilers are subjected to acute cold stress, broilers trained with cold stimulation have stronger lipid metabolism capacity. [ABSTRACT FROM AUTHOR]

A total of 240 healthy 1-day-old Ross 308 male broilers were randomly divided into 3 groups (CS0 group, CS3 group, and CS6 group), with 5 replicates in each group and 16 broilers in each replicate, in order to evaluate the effects of intermittent mild cold stimulation (IMCS) on the intestinal immune function and anti-cold stress ability of broilers after acute cold stress. The mRNA expression levels of cytokines and Toll-like receptors (TLRs) in the duodenum and jejunum were detected at the end of cold stimulation (36 d), 2 wk after recovery (50 d), and after acute cold stress (Y6). In addition, the mRNA and protein expression levels of heat shock proteins (HSPs) were measured before and after acute cold stress. The experimental data were statistically processed using 1-way ANOVA and Duncan's multiple comparisons. The results showed that the mRNA expression levels of IL2, IL8, IFN γ, TLR7, and TLR21 in the duodenum and IL2 and IFN γ in jejunum were significantly higher in the CS6 group than in the CS0 and CS3 groups at 36 d (P < 0.05). All TLR levels in the jejunum were significantly lower in the CS3 group than in the CS0 and CS6 groups at 36 d (P < 0.05). After 6 h of acute cold stress, in the duodenum, the mRNA expression levels of IL6 and IL8 were significantly decreased in the CS0 and CS6 groups compared to levels at 50 d (P < 0.05), while levels in the CS3 group remained stable (P > 0.05). Compared with 50 d, the expression level of HSP mRNA in the jejunum in the CS3 group was relatively stable compared to that in the CS0 and CS6 groups after acute cold stress (P > 0.05). At the protein level, the HSP60 expression level in the duodenum and HSP40, HSP60, and HSP70 expression levels in the jejunum were significantly higher in the CS3 group than in the CS0 and CS6 groups after acute cold stress (P < 0.05). In conclusion, cold stimulation training at 3℃/3 h lower than the conventional feeding temperature can improve the intestinal immune function and anti-stress ability of broilers. [ABSTRACT FROM AUTHOR]

To investigate the effect of intermittent cold stimulation on cardiac energy metabolism and cold resistance of broilers, 288 broilers were divided into 3 groups: control group (CC) and 2 cold stimulation groups (CS3 and CS9). The CS3 and CS9 groups received cold stimulation at temperatures of 3°C and 9°C lower than CC group for 5 h from d 15 to 35. Three groups were subjected to acute cold stress (ACS) of 10°C for 12 and 24 h at 44 d. Performance, cardiac histopathological changes, heat shock proteins (HSPs), and lipid metabolism levels were measured. Results showed that the performance was not different among groups at 22 and 29 d (P > 0.05), but the mRNA levels of Acyl CoA synthase long-chain family member 1 (ACSL1) and acyl-coenzyme oxidase (ACO) in CS group were upregulated compared to CC group (P < 0.05). At 36 d, the performance of the CS3 group was better than the other 2 groups, myocardial structure was normal and other lipid metabolism indexes, except for peroxisome proliferator-activated receptor coactivator 1α (PGC-1α) levels, were similar to those of CC group (P > 0.05). The myocardial fiber disorder, Triglyceride (TG), and leptin (LEP) contents were significantly lower in CS9 group than in CC and CS3 groups at 36 d (P < 0.05). The HSP protein levels were significantly higher in CS group than in CC group before ACS (P < 0.05). After 24 h of ACS, the mRNA of lipid metabolism genes, the protein levels of HSP40 and HSP60, and the contents of TG and LEP in the CS3 group were upregulated compared to other groups. The CC and CS9 groups showed myocardial structure was destroyed, with lower TG and LEP levels compared to before ACS (P < 0.05). Therefore, cold stimulation at 3°C lower than the normal feeding temperature for 5 h did not impair performance but can increase the resistance of broilers to ACS by promoting lipid metabolism. [ABSTRACT FROM AUTHOR]