Abstract: Maternal nutrition during late gestation and lactation profoundly influences the development of porcine offspring. This study investigated the effects of replacing a conventional corn-soybean meal diet (CON) with a sorghum-rice-barley (SRB) diet on sow lactation performance, maternal gut microbiota, and fecal metabolites, as well as on metabolic profiles in neonatal piglets. A total of 56 second-parity PIC hybrid sows were randomly assigned into two dietary treatment groups from day 112 of gestation until day 21 of lactation, with 28 sows per group. The SRB diet was formulated to have the same net energy content as the CON diet but with more fiber and slightly less crude protein. Compared to the CON group, sows on the SRB diet had significantly greater litter weight (P = 0.021) and individual piglet weight (P = 0.010) at weaning, as well as higher piglet average daily gain (P = 0.070). Microbial 16S rDNA sequencing revealed that the SRB diet increased the abundance of fiber-fermenting bacteria, including Subdoligranulum, Megasphaera, and Coprococcus (P < 0.05). Metabolomic analysis showed that the SRB diet significantly altered fecal metabolites associated with the serotonergic-synapse, bile-secretion, and phenylpropanoid-biosynthesis pathways. Notably, maternal fecal levels of 2-N-propylthiazolidine-4-carboxylic acid, N-hydroxy-L-tyrosine, and carnosol were positively correlated with concentrations of these metabolites in piglet plasma, suggesting potential vertical metabolite transfer. In conclusion, dietary inclusion of SRB positively reshapes maternal gut microbiota and metabolite profiles, consequently improving lactation efficiency and neonatal piglet growth. These effects may be partially mediated by the maternal microbiota-metabolite axis and the potential transfer of bioactive compounds from sows to offspring.