Raw feather is a favorable material for processing into feed rich in proteins convenient for nutrition of certain animals species. Since proteins of raw feathers are poorly digested, the improved digestibility of proteins may be achieved by hydrothermal processing of raw feathers. In this study the effect of water quantity at hydrothermal feathers treatment in industrial processing conditions on the nutritive value of hydrolysed feather meal was investigated. By these technological conditions in vitro digestibility of protein in hydrolysed feather meal was significantly increased in relation to digestibility of raw feathers. Hydrolysis contributes to the decrease of protein nitrogen content, whereas contents of non-protein nitrogen, ammonia and α-amino nitrogen were increased. Significant decrease of cystine content in the proteins of hydrolysates was noticed: 3.81, 4.07 and 4.21 g/100 g protein, depending on the technological treatments with the moisture content in raw feathers of 50%, 60% and 68%, respectively.