2.2. Collection of samples and preparation of sections
Blood samples from all geese were taken from the wing vein. After blood collection, samples were centrifuged at
200 × g for 20 min at 4 ◦ C and serum obtained was stored
at −20 ◦ C until assay. Ovarian and hypothalamic tissue samples were obtained from five Wanxi white geese in laying cessation stage. Tissue samples were fixed in 4% paraformaldehyde for 4 h, immersed in 30% sucrose in PBS overnight. Sections were sliced at 20 m thickness on a freezing microtome (Leica Microsystems, Wetzlar, Germany). Series of sections were collected into antifreeze solution (30% ethylene glycol; 25% glycerol; 0.05 M PB) and stored at −20 ◦ C until their use for immunofluorescence procedure.