The problem of collapsing in the fighting bull breed was conceived from a scientific point of view beginning in the thirties when different experts (Castejón y Martínez de Arizala, Peralbo, González Garcia, etc. (8) ) tried to give a solution based on explanations taken from pathology.
Since then numeous investigators, breeders and enthusiats have expressed their opinion and/or the results of their work and comments in this respect (4, 5, 6, 7, 8, 9, 10). It is common for then to refer directly or indirectly to the genetical component as an, influencing factor. However, only recently has experimental data been proposed which tries to explore the possible genetical bases of collapsing.