The present invention describes methods and processes for the production of proteins, particularly glycoproteins, by animal cell or mammalian cell culture, preferably, but not limited to, fed-batch cell cultures. In one aspect, the methods comprise the addition of glucocorticoid compound during the culturing period. The addition of glucocorticoid compound sustain a high viability of the cultured cells, and can yield an increased end titer of protein product, and a high quality of protein product, as determined, e.g., by sialic acid content of the produced protein.