Expression pattern of SMAD8 in geese at different reproductive stages and its effect on reproductive physiology and egg production performance

<b>Objectives: </b>To elucidate the role of <i>SMAD8</i> in geese egg production, we analyzed the expression patterns of <i>SMAD8</i> in geese during the egg-laying and non-laying periods. <b>Materials and Methods:</b> LDN-193189, a specific <i>SMAD8</i> inhibitor, was injected into the geese prior to the onset of egg-laying. Subsequently, the ovaries, oviducts, and serum of the geese at various reproductive stages were collected for subsequent detection and analysis. <b>Results:</b> The results indicated that the development of ovaries and oviducts in geese during the egg-laying period was superior to that during the non-laying period. In addition, <i>SMAD8</i> expression in ovaries and oviducts of egg-laying geese was significantly higher than that in non-laying geese (<i>p</i> < 0.05). Injection of the <i>SMAD8</i> inhibitor LDN-193189 at a dose of 0.15 mg/kg body weight per day significantly inhibited <i>SMAD8</i> expression. Concomitantly, the expression levels of follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) expression in the ovaries and oviducts were significantly increased (<i>p</i> < 0.05). Furthermore, the average egg production of geese was significantly increased by 4.1 eggs (<i>p</i> < 0.05), while the hatchability of breeder eggs remained unchanged (<i>p</i> > 0.05). Collectively, this study demonstrates that <i>SMAD8</i> is differentially expressed at different reproductive stages in geese. Exogenous <i>SMAD8</i> inhibitors can regulate <i>in vivo SMAD8</i> expression, thereby modulating the expression of ovulation-related hormone receptors and ultimately improving the goose egg production. <b>Conclusions:</b> These findings suggest that <i>SMAD8</i> may serve as a key intracellular regulator connecting reproductive organ development, hormone receptor abundance, and egg-laying performance in Wanxi White Goose (WWG) and indicate that targeted modulation of <i>SMAD8</i> activity could provide a novel strategy for boosting egg production in low-yield goose breeds without compromising hatchability.