“…These methods include (a) "gross protein value" (Anwar, 1960(Anwar, , 1961(Anwar, , 1962Duckworth er al., 1961;Boyne et al, 1961;Barnes and Woodham, 1963), (b) microbiological with Tetrahymena pyrformis (Stott et al, 1956;Boyne et a/., 1961), (c) enzymatic release of amino acids (Ingram et al, 1950;Jonsson, 1961 ;Ascarelli and Gestetner, 1962) and (d) carcass retention of nitrogen, referred to as "net protein value" (Fisher et a/., 1962) or "net protein utilization" (Braham et al, 1963).…”