A safety device for a feed dispensing and/or mixing machine, including a chamber (1), a gate (2) hingedly mounted thereon for loading and sealing the chamber, means (4, 10, 16, 18) for actuating the gate (2), means (6, 6a) for breaking up the materials in the chamber (1), and means (7a, 8, 5, 12, 6b) for actuating the breaking means. The device comprises means (32) for sensing the operative or inoperative state of the breaking means, means (26, 28) for sensing the open or closed position of the gate (2), and control means (24, 30, 34, 38) for preventing the gate (2) from being opened while the breaking means (6, 6a) are in operation, and enabling the gate to be opened once the breaking means are inoperative.