Body weight of newborn and suckling piglets affects their intestinal gene expression

At birth and during lactation phase, the light body weight of piglets born from hyperprolific sows predisposed to a higher expression of stress and pro-inflammatory genes. Modern hyperprolific sows must deal with large litters (16-20 piglets) which reduce piglet birthweight with a concomitant increase in the proportion of small and intrauterine growth retarded piglets. However, larger litters do not only have a greater variation of piglet weights, but also a greater variation in colostrum and milk consumption within the litter. To further understand the impact that body weight has on piglets, the present study aimed to evaluate the degree of physiological weakness of the smallest piglets at birth and during the suckling period (20 d) compared to their middle-weight littermates through their jejunal gene expression. At birth, light piglets showed a downregulation of genes related to immune response (FAXDC2, HSPB1, PPARGC1 alpha), antioxidant enzymes (SOD2m), digestive enzymes (ANPEP, IDO1, SI), and nutrient transporter (SLC39A4) (P < 0.05) but also a tendency for a higher mRNA expression of GBP1 (inflammatory regulator) and HSD11 beta 1 (stress hormone) genes compared to their heavier littermates (P < 0.10). Excluding HSD11 beta 1 gene, all these intestinal gene expression differences initially observed at birth between light and middle-weight piglets were stabilized at the end of the suckling period, when others appeared. Genes involved in barrier function (CLDN1), pro-inflammatory response (CXCL2, IL6, IDO1), and stress hormone signaling (HSD11 beta 1) over-expressed compared to their middle-weight littermates (P < 0.05). In conclusion, at birth and at the end of suckling period, light body weight piglets seem to have a compromised gene expression and therefore impaired nutrient absorption, immune and stress responses compared to their heavier littermates. Lay Summary Under hyperprolific situations, piglets must deal with a reduced birthweight and a severe sibling competition for nutrients. Therefore, light body weight newborn and suckling piglets may also have physiological disadvantages compared to their middle-weight littermates. To further understand the impact that body weight has on piglets, the present study aimed to evaluate the degree of physiological weakness of the smallest piglets at birth and during the suckling period (20 d) compared to their middle-weight littermates through their jejunal gene expression. Newborn light piglets downregulated genes related to immunity, antioxidant, and digestive activities, but also a tendency to upregulate other genes related to inflammation and stress responses. At the end of the suckling period, those genes expression differences vanished while others appear. Light weight piglets showed lower expression of genes involved in barrier function, inflammation, and stress responses compared to their middle-weight littermates. At birth and at the end of lactation, light piglets seem to have a compromised intestinal gene expression for nutrient absorption, immune and stress responses compared to their heavier littermates.