Heat stress is one of the adverse effects on productivity in the livestock. In pig, it is shown that the growth rate decreases under heat stress conditions. Moreover, it is reported that genetic variation is associated with heat stress tolerance. However, much less study has been done on identification of candidate genes and pathways associated with heat stress tolerance in pig. Here, this study aimed to identify the candidate genes and pathways associated with heat stress tolerance for growth rate in pig using microarray and RNA-seq. These methods were used to investigate differences in small intestine gene expression profiles among two finishing pig groups (high-tolerant and low-tolerant) with divergent heat stress tolerance for growth rate under heat stress conditions and control finishing pig group under non-heat stress conditions. The results of microarray and RNA-seq, respectively, showed that a total of 1277 genes for microarray and 2970 genes for RNA-seq were regarded as the genes showing heat stress responsive differential expression profiles associated with heat stress tolerance, and also 825 genes for microarray and 1233 genes for RNA-seq were upregulated and 452 genes for microarray and 1737 genes for RNA-seq were downregulated in hightolerant group as compared to low-tolerant group. Among these genes, we found overrepresentation of a set of genes involved in TGFβ signaling pathway. The gene set exhibited differential expression profiles between hightolerant and low-tolerant groups which are reported to lead to activation of TGFβ signaling pathway, resulting in cell differentiation and regeneration of intestinal cell in hightolerant group. These results suggested that the TGFβ signaling pathway was identified as the intriguing pathway showing heat stress-responsive activation associated with heat stress tolerance for growth rate in small intestine of finishing pig.

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