A mobile and modular device with movable walls for the dynamic weighing of a bovine animal includes an identification module having a support structure, a processing module, a solar panel, an antenna and an identifier; and a weighing module including a base, a pair of side walls, a weighing platform, a pair of load cells and an amplifier and transmission box. The processing module, the identifier, the solar panel and the antenna are associated on the support structure. The weighing platform, the pair of load cells and the amplifier and transmission box are associated on the base in a fixed way. Each one of the pair of side walls contains a fixed portion and a mobile portion; and each one of the lower ends of the fixed portion contains a mechanism, which is associated to the base in a mobile way, through a first distal end and a second distal end.