Method of culturing embryonic stem (ES) cells of avian origin includes the steps of: a) suspending ES cells originating from the blastoderm disk of fertilized un-incubated avian egg(s) in a basal culture medium supplemented with: insulin-like growth factor-1 (IGF-1) and ciliary neurotrophic factor (CNTF); and animal serum; and, optionally, at least one growth factor selected from among interleukin 6 (Il-6), interleukin 6 receptor (Il-6R), stem cell factor (SCF), fibroblast growth factor (FGF), leukemia inhibitory factor (LIF), interleukin 11 (Il-11), oncostatin and/or cardiotrophin; b) seeding the suspension of ES cells obtained in step a) on a layer of feeder cells and further culturing the ES cells for at least 2 to 10 passages; c) optionally, removing at least one growth factor selected from among SCF, FGF, Il-6, Il-6R, LIF, oncostatin, cardiotrophin and Il-11 from the culture medium; and d) further culturing the ES cells in the medium of step c) on a layer of feeder cells.