Effects of dietary methionine on productivity, reproductive performance, antioxidant capacity, ovalbumin and antioxidant-related gene expression in laying duck breeders

The study investigated whether dietary methionine (Met) affects egg weight and antioxidant status through regulating gene expression of ovalbumin (OVAL), nuclear factor erythroid 2 like 2 (Nrf2) and haem oxygenase 1 (HO-1) in laying duck breeders. Longyan duck breeders (n 540, 19 weeks) were randomly assigned to six treatments with six replicates of fifteen birds each. Breeders were fed diets with six Met levels (2·00, 2·75, 3·50, 4·25, 5·00 and 5·75 g/kg) for 24 weeks. The egg weight (g), egg mass (g/d), feed conversion ratio, hatchability, 1-d duckling weight, albumen weight, albumen proportion and OVAL mRNA level improved with dietary Met levels, whereas yolk proportion decreased (P