Heat-induced protein oxidation of soybean meal impairs growth performance and antioxidant status of broilers

This study aimed to evaluate the impact of oxidative modification on soybean meal (SBM) proteins after exposure to different heating times, and the effects of the oxidized SBM on the growth performance [average daily feed intake (ADFI), average daily gain (ADG), and feed to gain ratio (F: G)], oxidative redox status [(reactive oxygen species (ROS), total antioxidant capacity (TAC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), and protein carbonyl (PC)]. A total of 400 one-day-old Arbor Acres chicks were randomly divided into 5 treatment groups with 8 replicates of 10 birds each. Birds in the control group (CON) were fed diet containing non-heated SBM, and those in the treatment groups were fed SBM heated at 100°C for 1, 2, 4, and 8 h, for 42 d. Heated SBM (HSBM) showed a relatively higher PC content in vitro. The ADG decreased, whereas the F:G increased linearly with an increase in heating time during the starter (days 1 to 21), grower (days 22 to 42), and the overall growth phases (days 1 to 42; P < 0.05). However, the ADFI decreased linearly only during the grower phase (P < 0.05). The plasma, liver, and jejunum ROS levels, MDA concentrations, and PC contents increased linearly (P < 0.05) in broilers fed HSBM. Furthermore, the TAC in the plasma and jejunum, and the total SOD and GSH-Px activities in the plasma, liver, and jejunum decreased linearly (P < 0.05) in broilers when feeding HSBM. (P < 0.05). The mRNA level of Nrf2 in the liver and jejunum was lower (P < 0.05) in broilers fed diet containing the SBM after 8 h heat-treatment than in those fed the CON diet at days 42. This study suggested that heat-induced protein oxidation of SBM could decrease growth performance and impair antioxidant status of broilers.