With the presence of global warming, the occurrence of extreme heat is becoming more common, especially during the summer, increasing pig susceptibility to severe heat stress. The aim of the current study was to investigate changes in morphology and gene expression in the pig small intestine in response to heat stress. Forty eight Chinese experimental mini pigs (Sus scrofa) were subjected to 40 degrees C for 5h each day for 10 successive days. Pigs were euthanized at 1, 3, 6, and 10 days after heat treatment and sections of the small intestine epithelial tissue were excised for morphological examination and microarray analyses. After heat treatment, the pig rectal temperature, the body surface temperature and serum cortisol levels were all significantly increased. The duodenum and jejunum displayed significant damage, most severe after 3 days of treatment. Microarray analysis found 93 genes to be up-regulated and 110 genes to be down-regulated in response to heat stress. Subsequent bioinformatic analysis (including gene ontology and KEGG pathway analysis) revealed the genes altered in response to heat stress related to unfolded protein, regulation of translation initiation, regulation of cell proliferation, cell migration and antioxidant regulation. Heat stress caused significant damage to the pig small intestine and altered gene expression in the pig jejunum. The results of the bioinformatic analysis from the present study will be beneficial to further investigate the underlying mechanisms involved in heat stress-induced damage in the pig small intestine.
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