Novel insights into the transcriptomic changes of the hypothalamus in broilers exposed to high-density stocking

Background The prevalence of high stocking density ( HD ) in the broiler industry has been significantly increased, exerting profound implications for the physiology, behavior, and welfare of chickens, particularly concerning the regulation of their nervous system, specifically the central nervous system. Conversely, the impact of HD stress on the neurophysiological function of the broiler hypothalamus remained unknown. Results This study was conducted to investigate the effects of varying stocking densities on growth performance, serum biochemistry, and hypothalamic transcriptome in chickens across distinct developmental stages, specifically at 21, 28, 35, and 42 days of age. Two density conditions were utilized: normal density (ND) at 14 birds per square meter (m²) and high density (HD) at 22 birds per square meter (m²). Results indicated that no significant differences in growth performance were observed during the initial 21 days; however, significant reductions in body weight and feed intake were observed in the HD group from days 22 to 42. At 35 and 42 days of age, serum concentrations of IL-4 and TNF-α were significantly elevated in the HD group compared to the ND group. Gene mapping success rates were observed to range from approximately 37.44–92.93%. A total of 42.48 million raw sequencing reads were generated per sample. Significant differential enrichment in KEGG pathways was detected between the ND and HD groups on days 21, 28, 35, and 42. Significant alterations were identified across several key signaling pathways, including pyruvate metabolism; oxidative phosphorylation; alpha-linolenic acid metabolism; neuroactive ligand-receptor interactions; Wnt signaling; Notch signaling; and apoptosis signaling. Candidate genes including SMAD3 , PPY , SLCO1C1 , Wnt16 , and NMU were identified as critical for central nervous system immunity. Furthermore, NPY, STAT2, SLC26A3 , and ISL2 regulate feeding behavior. Conclusions These findings provide critical insights for investigating the effects of HD stress on broiler growth performance, serum biochemical parameters, and hypothalamic transcriptome.