Synergistic effects of dietary methionine and taurine on growth performance, blood parameters, expression in hepatic sulfur-metabolism genes, and flesh quality of large Nile tilapia

This study aimed to evaluate the growth performance, expression of genes related to the metabolism of sulfur-containing amino acids, and flesh quality of large Nile tilapia ( Oreochromis niloticus ). Fish (n = 120; 1199 ± 46 g) were randomly distributed into four groups and each fish group was hand-fed a basal diet not supplemented (CON) or supplemented with methionine (MET), taurine (TAU), and methionine and taurine (MET+TAU) until apparent satiety for seven weeks. Compared to CON group, the fish group on the MET diet experienced increased in final body weight, protein retention efficiency, and fillet yield by 62.83 g, 9.82%, and 1.31%, respectively ( p < 0.05). These results were linked to the down-regulation of cystathionine β-synthase (CBS) and cysteine dioxygenase (CDO) gene controlled by methionine supplementation. Moreover, up-regulation of the adenosylhomocysteine (AHCY) gene in fish offered TAU diet as a metabolic response to methionine deprivation. Furthermore, taurine prevented color deterioration and increased fillet hardness and chewiness attributes as compared to CON group ( p < 0.05). Overall, this study indicated a marked effect of dietary methionine on growth performance, particularly fillet yield, and notable synergic effect of methionine and taurine preventing color deterioration and increasing fillet hardness. • Methionine enhanced growth, feed efficiency, protein retention, and fillet yield of fish. • Fish fed methionine supplemented diets showed down-regulated expression of CBS and CDO genes . • Taurine addition increased mRNA levels of AHC gene in response to methionine deprivation. • Methionine and taurine in combination effectively prevented color deterioration and enhanced fillet hardness and chewiness.