Review: Research progress on broodiness behavior and its molecular mechanisms in poultry

Broodiness is a natural maternal behavior exhibited by female poultry, characterized by increased time spent sitting on the nest, feather fluffing, decreased appetite, cessation of egg-laying, and incubation behavior. The broodiness characteristics of female poultry are primarily regulated by external environmental factors and internal factors (such as genetics and hormones), and are regulated at the organ, cell, and molecular levels. At the organ level, the hypothalamic-pituitary-ovarian (HPO) axis plays a crucial role in regulating broodiness behavior. At the cellular level, hypothalamic hormones (such as GnRH), pituitary hormones (such as PRL, FSH, and LH), and gonadal hormones (such as estrogen and progesterone) bind to corresponding receptors on the cell membrane, activating different signaling pathways to regulate the apoptosis and autophagy of granulosa cells (GCs), thereby influencing the occurrence of broodiness behavior. At the molecular level, broodiness behavior in avian species is a complex trait controlled by multiple genes, with epigenetics playing a key role in the regulation of gene expression. However, the exact regulatory mechanisms of how these factors affect the ovarian structure and function, and consequently lead to broodiness behavior, remain unclear. Therefore, this paper discussed the characteristics of poultry broodiness behavior, the morphological changes in the reproductive system before and after broodiness, and provided a review of the regulatory mechanisms at the organ, cellular, and molecular levels, aiming to provide a reference for future research on poultry broodiness.