Effects of folic acid supplementation to basal diets of broilers on growth performance, slaughter performance, IGF2 gene expression and methylation

Folic acid (FA) is an important water-soluble vitamin and plays an important role as a cofactor and coenzyme in animal growth and development, and regulation of gene expression and methylation. A total of 270 female broiler chickens (1-day-old) were randomly allotted to three dietary treatments supplemented with 0 mg/kg (control group), 5 mg/kg, and 10 mg/kg FA in basal diets for 42 days, respectively. Each treatment had six replicate cages with 15 birds per cage. Dietary supplementation of 5 mg/kg FA significantly enhanced average body weight and average daily gain of 21-day-old broilers (P < 0.05), but significantly reduced subcutaneous fat thickness and widths of an intermuscular fat band of 42-day-old broilers by dietary FA treatments (P < 0.05). Also, a diet with 10 mg/kg FA supplementation significantly increased the relative heart weight of 42-day-old chickens (P < 0.05). Furthermore, dietary FA supplementation significantly improved the serum insulin-like growth factor 2 (IGF2) concentrations (P < 0.01) and IGF2 mRNA expression in the abdominal fat (P < 0.05), but no statistical differences were found in the methylation of IGF2 promoter (P > 0.05). The present study demonstrated that dietary FA supplementation may have positive effects on chicken growth through increased IGF2 gene expression.