Thermal manipulation during broiler chicken embryogenesis increases basal mRNA levels and alters production dynamics of heat shock proteins 70 and 60 and heat shock factors 3 and 4 during thermal stress

This study investigated the effects of thermal manipulation (TM) during embryonic days 12 to 18 on the cloacal temperature (T-c ) and the kinetics of muscle mRNA levels of heat shock proteins 70 and 60 (Hsp70 and Hsp60) and heat shock factors 3 and 4 (HSF3 and HSF4) during the first week of life and during thermal stress (TS). One thousand five hundred fertile chicken eggs were randomly divided into 5 groups: control group (37.8 degrees C), TM1 (38.5 degrees C for 18 h), TM2 (39 degrees C for 18 h), TM3 (39.5 degrees C for 18 h), and TM4 (40 degrees C for 18 h). On post-hatch days 14 and 28 of age, 30 randomly selected chicks from each group were thermally stressed at 41.0 degrees C for 6 h, while another 30 randomly selected chicks from each group were kept under thermo-neutral conditions. The T-c of TM chicks was only numerically lower than that of the control during the study period. However, during TS at days 14 and 28 of age, the TI of TM chicks was significantly lower than that of the controls. On post-hatch days 14 and 28, the basal mRNA levels of Hsps and HSFs were significantly higher than those of the control. Furthermore, during TS, rapid increases in the mRNA levels of Hsps and HSFs in the TM groups were observed. These results indicate that, as well as altering their basal mRNA levels during the first week post-hatch, TM also altered the dynamics of the mRNA expression of HSPs and HSFs, which was associated with improved acquisition of thermotolerance during TS.