A transcriptomic analysis of gut response to stress induced by weaning in piglets.

Weaning is a critical period for piglets, typically accompanied by low feed intake, weight loss and increased mortality. In this period the gut undergoes morphological and histological changes that include reduction of villous height and increase in crypt depth. Antibiotics used in the past to mitigate weaning problems have been recently replaced by organic acids, to avoid the selection and spread of antibiotic-resistant pathogenic strain. The aim of this study was to investigate changes in gene expression induced by the stress of weaning and by the inclusion of sorbic acid in the diet during this critical period. Sixteen female piglets were sacrificed during the experiment: 4 before weaning (T0) and 12 five days after weaning (T5). The T5 group was split in two subgroups, one receiving a standard diet containing 5 g/kg of sorbic acid, and the other receiving the same diet in which organic acid was replaced by barley flour. Gene expression was measured in the ileum using Combimatrix whole transcriptome microarrays. No significant difference was found between diets in term of gene expression, metabolism and histology. This probably as a consequence of the short period of treatment and of the severe stress provoked by weaning that likely masked the effect of the different diets. Conversely, 205 genes were found differentially expressed between T0 and T5. These mediate piglet stress response and metabolic adaptation to a new diet and environment during weaning. Gene ontology (Blast2Go software), pathway and network analyses (IPA software) of differentially expressed genes indicated the activation of several important pathways related to immune and inflammatory response. Transcriptome analysis well described the biological response to stress of piglets in this critical life stage and will be useful to test the effects of specific nutrients or additives (including pre- and pro-biotics) designed to mitigate the stress-induced inflammatory response in the gut and to improv