Transcriptome profiling of the pituitary gland reveals candidate genes for divergent feed efficiency in slow-growing chickens

Feed efficiency (FE) is a critical trait in poultry production, including slow-growing chicken breeds such as the Korat (KR) chicken. In this study, transcriptome profiling of the pituitary gland was performed to investigate the molecular mechanisms underlying FE differences between low residual feed intake (LRFI) and high residual feed intake (HRFI) groups. A total of 22 differentially expressed genes (DEGs) were identified, with three upregulated and 19 downregulated in the LRFI group. Among them, thyrotropin-releasing hormone receptor 3 (TRHR3), a gene associated with metabolic regulation in the pituitary, was significantly downregulated in the LRFI group, while elevated plasma levels of tetraiodothyronine (T4). Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis on gene sets revealed that better FE in KR chickens is related to linoleic and alpha-linolenic acid metabolism, as well as steroid hormone biosynthesis, highlighting their roles in thyroid hormone secretion, muscle development, and lipid metabolism. Unravelling pathways and key genes which are involved in variation of RFI in KR chickens will be useful to search for candidate DNA markers in the parental lines in order to improve FE of the KR chicken.