Low birth weight female piglets show altered intestinal development, gene expression, and epigenetic changes at key developmental loci.

Intestinal development is compromised in low birth weight (LBW) pigs, negatively impacting their growth, health, and resilience. We investigated the molecular mechanisms of the altered intestinal maturation observed in neonatal and juvenile LBW female piglets by comparing the changes in intestinal morphology, gene expression, and methylation in LBW versus normal birth weight (NBW) female piglets. A total of 16 LBW/NBW sibling pairs were sacrificed at 0 hours, 8 hours, 10 days, and 8 weeks of age. The gastrointestinal tract was weighed, measured, and the small intestine was sampled for histomorphology, gene expression, and methylation analyses. Impaired intestinal development, with shorter villi and shallower crypts, was observed in LBW female piglets. The expression of intestinal development markers (ALPI and OLFM) rapidly peaked after birth in NBW but not in LBW female piglets. The lower expression of genes involved in nutrient digestion (ANPEP and SI) and barrier function (OCLN and CLDN4) in LBW, together with their delayed development of intestinal villi and crypts could help to explain the compromised health and growth potential of LBW female piglets. The changes in methylation observed in LBW in key regulators of intestinal development (OLFM4 and FZD5) suggest long-term effects of BW on intestinal gene expression, development, and function. Accordingly, experimental demethylation induced in IPEC-J2 cells led to increased expression of intestinal genes (MGA, DPP4, and GLUT2). Overall, we have identified the alterations in transcription or epigenetic marking at a number of genes critical to intestinal development, which may contribute to both the short- and long-term failure of LBW female piglets to thrive.