Poultry production increasingly relies on nutritional strategies to improve growth efficiency and health, with growing interest in phytobiotics and methyl-donor nutrients that modulate physiological and molecular pathways. This study investigated the integrated physiological, molecular, and intestinal responses of broiler chickens to dietary supplementation with DL-methionine, betaine, and turmeric extract. A total of 108 one-day-old Hubbard broiler chicks were randomly allocated to four dietary treatments, each comprising three replicates of nine birds: a basal control diet and diets supplemented with DL-methionine (1 g/kg), betaine (1 g/kg), or turmeric extract (200 mg/kg). Growth performance was recorded throughout the experimental period, and blood, breast muscle, and intestinal samples were collected at 35 days of age for biochemical, gene expression, and histomorphological analyses. Dietary supplementation significantly improved final body weight, body weight gain, and feed conversion ratio (P