This study aimed to investigate the effects of thermal conditioning and folic acid on the methylation levels of the avian brain-derived neurotrophic factor (BDNF) promoter region at the M3 and M9 positions in the early life of broiler chicks. In Experiment 1, male broiler chicks (day 3 oflif e) were orally injected with methyl cellulose solution with or without folic acid (25 mg). The chicks in the heat-treatment groups were immediately exposed to a high ambient temperature (40 +/- 0.5 degrees C) for 12 h, while chicks in the non-heat treatment groups were left in the thermoneutral zone (30 +/- 0.5 degrees C). The groups were as follows: 1) no thermal conditioning group without folic acid (control), 2) thermal conditioning group without folic acid, 3) no thermal conditioning group with folic acid, and 4) thermal conditioning group with folic acid. In Experiment 2, treatments were similar to those in Experiment 1, except for the usage of female chicks. After the treatments, the methylation levels of the BDNF promoter in chicks were determined using semiquantitative PCR. There were no significant differences between groups in the levels of methylation at the M3 position in both males and females as a result of thermal conditioning and folic acid treatment. Interestingly, significant effects of thermal conditioning and folic acid treatment on methylation at the M9 position were found. BDNF methylation levels at M9 significantly decreased following thermal conditioning, while folic acid suppressed demethylation in both male and female chicks. These data suggest that folic acid and thermal conditioning affects DNA methylation patterns in the central nervous system ofchicks, regardless of sex.
