Appropriate cold stimulation changes energy distribution to improve stress resistance in broilers

Intermittent mild cold stimulation can improve energy metabolism in the livers of broilers and the stress resistance to adapt to low-temperature environment and build cold adaptation. Appropriate cold stimulation can improve stress resistance in broilers and alleviate the adverse impacts of a cold environment. To investigate the effects of intermittent mild cold stimulation (IMCS) on energy distribution in the livers of broilers, 96 healthy 1-d-old Ross-308 male broilers were randomly divided into the control group (CC) and the cold stimulation group (H5). The CC group was raised at a normal thermal temperature, i.e., 35 & DEG;C until 3 d, after which the temperature was dropped gradually by 0.5 & DEG;C/d until 20 & DEG;C at 33 d. This temperature was maintained until 49 d. The H5 group was raised at the same temperature as the CC group until 14 d (35 to 29.5 & DEG;C) and at 3 & DEG;C below the temperature of the CC group starting at 0930 hours for 5 h every other day from 15 to 35 d (26 to 17 & DEG;C). The temperature was returned to 20 & DEG;C at 36 d and maintained until 49 d. At 50 d, all broilers were subjected to acute cold stress (ACS) at 10 & DEG;C for 6 and 12 h. We found that IMCS had positive effects on production performance. Using transcriptome sequencing of the broiler livers, 327 differentially expressed genes (DEG) were identified, and highly enriched in fatty acid biosynthesis, fatty acid degradation, and the pyruvate metabolism pathway. When compared to the CC group, the mRNA levels of ACAA1, ACAT2, ACSL1, CPT1A, LDHB, and PCK1 in the H5 group were increased at 22 d (P < 0.05). The LDHB mRNA level was upregulated in the H5 group at 29 d compared to the CC group (P < 0.05). After 21 d of IMCS (at 36 d), the mRNA expression levels of ACAT2 and PCK1 were found to be significantly increased in the H5 group compared to the CC group (P < 0.05). Seven days after the IMCS had ended (at 43 d), the mRNA levels of ACAA1, ACAT2, and LDHB in the H5 group were higher than in the CC group (P < 0.05). The mRNA levels of heat shock protein (HSP) 70, HSP90, and HSP110 in the H5 group were higher than in the CC group after 6 h of ACS (P < 0.05). The protein levels of HSP70 and HSP90 in the H5 group were downregulated after 12 h of ACS, compared to the CC group (P < 0.05). These results indicated that IMCS at 3 & DEG;C lower than the normal temperature could improve energy metabolism and stress resistance in the livers of broilers, alleviate the damage of short-term ACS on broilers, help broilers adapt to the low temperature, and maintain stable of energy metabolism in the body. Lay Summary Cold stimulation has a great impact on broilers. Excessive cold stimulation can lead to damage, while intermittent mild cold stimulation (IMCS) can make broilers adapt to the cold environment. Low temperature will make the body produce lots of heat to maintain metabolic stability. The liver controls the energy metabolism, and the avian livers are the main organ regulating lipid metabolism. In this study, the broilers of different ages were subjected to cold stimulation training and then acute cold stress (ACS). We found that IMCS had positive effects on production performance. Through transcriptome sequencing, we found that the differentially expressed genes were highly enriched in the energy metabolism pathway, and the expression levels of the most key genes and heat shock proteins were upregulated. The stress resistance was also enhanced, which could alleviate the damage of short-term ACS to the body. The broilers gradually adapted to the low-temperature environment and finally established cold adaptation. The findings of this work will be helpful to the development of animal husbandry in cold regions and improve animal welfare.