Impact of sulfur-containing amino acids on the plasma metabolomics and intestinal microflora of the sow in late pregnancy

Sulfur-containing amino acids (SAAs) such as methionine (Met) and cysteine (Cys) are involved in the control of oxidative states and may serve as mediators of metabolism and cellular functions. The purpose of this study was to evaluate the influence of different Met/Cys ratios (46% Met, 51% Met, 56% Met, and 61% Met, with Met accounting for 0.78% of the total SAAs and Cys for the remainder; see Methods section for details) on the plasma metabolomics, intestinal microflora of the sow in late pregnancy and survival rate of piglets. The results demonstrated that the 51% Met group increased the survival rate of piglets and improved the level of low-density lipoprotein, albumin, and phosphorus of serum in comparison with the 56% Met group. The resulting plasma metabolomic profile indicated that the 51% Met group had enhanced levels of β-alanine, uracil, hydrouracil, phosphoserine, vitamin D3, and α-tocotrienol compared with the 46% Met group. Moreover, the ratio of Bacteroidetes and Firmicutes was increased in the 51% Met and 62% Met groups in relation to the 56% Met group. In addition, Pearson's correlation analysis found that there were negative correlations between vitamin D3 and Ruminococcaceae_UCG-002 and between α-tocotrienol and Ruminococcaceae_UCG-002; there was a positive correlation between allantoin and Parabacteroides spp. These results suggested that 51% Met is the optimal Met/Cys ratio for sows in late pregnancy, because it increased the survival percentage of piglets and enhanced the increase in serum metabolites required for optimal sow health during late pregnancy.