Intrauterine growth restriction, defined by an elevated brain-to-liver weight ratio, affects faecal microbiota composition and, to a lesser extent, plasma metabolome profile at different ages in pigs

Abstract Background Intrauterine growth restriction (IUGR) affects up to 30% of piglets in a litter. Piglets exposed to IUGR prioritize brain development during gestation, resulting in a higher brain-to-liver weight ratio (BrW/LW) at birth. IUGR is associated with increased mortality, compromised metabolism, and gut health. However, the dynamic metabolic and microbial shifts in IUGR-affected pigs remain poorly understood. This study aimed to investigate the longitudinal effects of IUGR, defined by a high BrW/LW, on the composition of faecal microbiota and plasma metabolome in pigs from birth to slaughter. One day (± 1) after birth, computed tomography was performed on each piglet to assess their brain and liver weights. The pigs with the highest (IUGR = 12) and the lowest (NORM = 12) BrW/LW were selected to collect faeces and blood during lactation (day 16 ± 0.6, T1) and at the end of the starter period (day 63 ± 8.6, T2) and faeces at the beginning (day 119 ± 11.4, T3) and end of the finisher period (day 162 ± 14.3, T4). Results Faecal microbial Alpha diversity remained unaffected by IUGR across all time points. However, the Beta diversity was influenced by IUGR at T1 (P = 0.002), T2 (P = 0.08), and T3 (P = 0.03). Specifically, IUGR pigs displayed higher abundances of Clostridium sensu stricto 1 (P adj = 0.03) and Romboutsia (P adj = 0.05) at T1, Prevotellaceae NK3B31 group (P adj = 0.02), Rikenellaceae RC9 gut group (P adj = 0.03), and Alloprevotella (P adj = 0.03) at T2, and p-2534-18B5 gut group (P adj = 0.03) at T3. Conversely, the NORM group exhibited higher abundances of Ruminococcus (P adj = 0.01) at T1, HT002 (P adj = 0.05) at T2, and Prevotella_9 (P adj