1. A study was conducted to evaluate the effects of two hatching weight (HW) levels and two dietary concentrations of
methionine on the growth performance and oxidative status of broilers. Male Arbor Acres chickens were divided into two groups on their HW (low and high HW, H and L). Each HW group was then distributed into two subgroups, of similar HW, receiving either low or high dietary concentrations of
methionine (4.9 g
methionine/kg, LM; 5.9 g
methionine/kg, HM). Thus, all day-old birds were distributed into 4 treatments (H-LM, H-HM, L-LM, L-HM) × 6 replicates × 10 birds for 21 d. 2. Broilers with high HW were heavier than those with low HW during the 21 d assay, which appeared to result from increased
body weight gain rather than improved feed conversion efficiency. A higher dietary concentration of
methionine (5.9 g/kg) improved growth performance of broilers with low HW in terms of
body weight gain and feed conversion ratio. 3. Broilers with different HW had similar
antioxidant status both in serum and liver. 4. Broilers given a diet containing 5.9 g/kg
methionine had enhanced serum
superoxide dismutase (SOD) activity and decreased hepatic
malondialdehyde (MDA) content at day 7. 5. Broilers given a diet containing 5.9 g/kg
methionine had a higher hepatic
reduced glutathione (GSH):
glutathione disulphide (
GSSG) ratio than those given a diet containing 4.9 g/kg
methionine at day 21. High dietary
methionine concentration reduced hepatic GSH content and
glutathione peroxidase (GPX) activity of broilers with high HW at day 7 and at day 21, respectively, but increased hepatic GSH content of broilers with low HW at day 7. 6. Although broilers with different HW had similar oxidative status as indicated by several parameters in blood and liver, HW can have positive effects on the subsequent growth performance of broilers, and a higher dietary
methionine concentration (5.9 g/kg) can improve growth performance and
antioxidant status in broilers exhibiting low HW.