Supplementing RP-Arg during the gestation and lactation periods of grazing sheep reprograms liver metabolism in offspring lambs by increasing IGF-1 in milk

The nutritional status of ewes during gestation and lactation is a key determinant of lamb growth performance. Supplementing rumen-protected arginine (RP-Arg) during these stages induces maternal metabolic adaptation, thereby maintaining fetal developmental homeostasis. However, the sustained effects of such metabolic regulation on postnatal lamb growth and immune function remain unclear. This study employed a combined comparative approach of 16S rRNA sequencing and metabolomics analysis to reveal differential effects of concentrate supplementation and RP-Arg on offspring gut microbiota restructuring and hepatic metabolic reprogramming. Compared to the CON group, both the SF (CON + concentrate) and ARG (SF + RP-Arg) groups significantly improved early growth performance in lambs (P < 0.05), with the ARG group exhibiting a significantly higher growth rate than the SF group (P < 0.05). Milk protein content was significantly increased in the SF and ARG groups relative to the CON group (P < 0.05). Notably, compared to the SF group, ARG supplementation elevated colostrum lactoferrin (LF) and insulin-like growth factor-1 (IGF-1) concentrations by 28.4% and 34.1%, respectively (P < 0.05). 16S rRNA sequencing revealed significant enrichment of the Bacteroidetes phylum following RP-Arg supplementation. Liver metabolomics analysis revealed that RP-Arg synergistically promotes offspring growth advantage and immune maturation by enhancing amino acid digestion efficiency, transmembrane transport capacity, and metabolic flux redistribution. This study elucidates a novel maternal-fetal interaction mechanism: strategically incorporating RP-Arg into sheep diets during the reproductive cycle modulates ewe colostrum composition and lamb gut-liver axis function, ultimately synergistically optimizing growth trajectories and immune development within grazing systems.