Effect of methionine replacement with taurine on the performance and antioxidative capacity of broiler

Methionine (Met) affects growth performance and contributes to glutathione (GSH) synthesis, which serves as an antioxidant and enhances the activity of the antioxidant system. Taurine (TAU) is synthesizable in the chickens' bodies by combining Met and sulfur; however, it is unknown how TAU as a replacement of Met affects growth performance and antioxidant capacity in broilers. The study investigated the impact of replacing Met with TAU on the growth and antioxidant capacity of broilers. A basic diet was used for the control group, and diets where 15%, 30%, and 45% of crystallized Met was replaced with TAU for the treatment groups. TAU substitution did not affect the performance of chicks (P > 0.05). The malondialdehyde (MDA) content in the liver significantly decreased by 26.8% in 45TAU and 17.5% in 15TAU (P < 0.05). In thigh muscle, MDA was reduced by 58.9% in 15TAU (P < 0.05). In the liver, the catalase activity declined significantly by 37.4% in 15TAU (P < 0.05), 48.5% in 30TAU (P < 0.05), and 48.6% in 45TAU (P < 0.05). In thigh muscle, superoxide dismutase significantly decreased by 33% in 15TAU (P < 0.05), 40.6% in 30TAU (P < 0.05), and 43% in 45TAU (P < 0.05). GSH in thigh muscle declined by 28.2% in 15TAU (P < 0.05), 37.5% in 30TAU (P < 0.05), and 39.8% in 45TAU (P < 0.05). In thigh muscle, glutathione peroxidase significantly decreased by 38% in 15TAU (P < 0.05), 44.3% in 30TAU (P < 0.05), and 34.7% in 45TAU (P < 0.05). The 45TAU group increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) in the liver (P < 0.05); however, the 30TAU group showed improved expression of glutathione reductase and superoxide dismutase 2 (P < 0.05). In thigh muscle, the protein level of Nrf2 increased in the 45TAU and 15TAU (P < 0.05). The result indicates that the effect of TAU replacement of Met on antioxidant capacity is tissue-specific. The result suggests that Met could be partially replaced by TAU without adverse effect on growth performance, whereas TAU cannot fully replace the role of Met in antioxidant function. The role of TAU in the antioxidant system and the synergistic role with Met need to be investigated further.