Intermittent cold stimulation acclimates broilers to acute cold stress by affecting cardiac lipid metabolism.

Objective: This study aimed to investigate whether intermittent cold stimulation can induce adaptation in broilers to acute cold stress (ACS) by regulating the lipid metabolism of hearts.

Methods: CS0 were kept at normal rearing temperature, while CS3 and CS5 were exposed to 3°C for 3 and 5 hours, respectively, on alternate days lower than CS0 from 15d to 35d. On 50d, broilers in three groups were exposed to ACS at 10°C for 12 hours (Y12). The levels of corticosterone (CORT) and liothyronine (T3), mRNA and protein levels of heart adenosine monophosphate (AMP)-activated protein kinase/mammalian target of rapamycin (AMPK/mTOR) pathway genes were assessed at 36 d, 50 d and Y12.

Results: At 36d, mRNA levels of AMPKα, acyl-CoA oxidase (ACO), mTOR, sterolregulatory element binding protein (SREBP), stearoyl-coA desaturase (SCD), acetyl-coA carboxylase (ACC), fatty acid synthase (FAS) and protein level of peroxisome proliferatorsactivated receptor α (PPARα) in CS3 and CS5 were significantly lower than those in CS0 (p<0.05). At 50d, compared to CS0, mRNA levels of PPARα, carnitine palmitoyltransferase1 (CPT1), ACO, tuberous sclerosis complex (TSC), SREBP and SCD, as well as protein levels of p-AMPKα/AMPKα, PPARα and SREBP were significantly increased in CS5 (p<0.05). At Y12, the levels of T3 in CS3 and CS5 were significantly higher than those in CS0 (p<0.05), mRNA levels of CPT1, ACO, SREBP, SCD and protein levels of p-AMPKα/AMPKα, SREBP, and FAS were significantly higher in CS5 than in CS0 and CS3 (p<0.05). However, compared to 50d, at Y12, mRNA levels of AMPKα, CPT1 and ACO in CS3 and CS5 significantly decreased (p<0.05), while protein levels of p-AMPKα/AMPKα significantly increased (p<0.05).

Conclusion: This study suggested that intermittent cold stimulation at 3°C lower than normal rearing temperature for 5h could help broilers adapt to the ACS by promoting heart lipid metabolism.