Disclosed is an assembly consisting of a passageway (8) from a first space to a second space, delimited by side delimitations, for livestock, such as cattle. A gate system (3) is mounted in the passageway, the system having at least one self-closing gate leaf (6a, 6b) which is movable between a closed position and one or more open positions, including a pass position in which an animal can pass from the livestock passage to the second space. The gate leaf is arranged for movement to an open position by the exertion of pressure by an animal from the livestock passing through the passageway to the second space. The assembly is also provided with means (16) for determining an ID of an animal from the livestock, and in response to data from the ID determining means, means (7a, 7b) for blocking the gate leaf from moving into a pass position can be activated.
