Based on the need to know the physical variations of a feed for beef cattle in a confinement system, which is necessary due to the natural behaviour of the species and the existing group hierarchy, a total diet consisting of concentrated feed plus roughage, its variations and the animals' behaviour towards the feed were evaluated for approximately 12 hours. The work was carried out during a feed efficiency test of young cattle (approximately 15 months old) of the Senepol breed, in order to select the best animals in the group and include them in breeding programmes for genetic improvement of the breed, by means of feed efficiency measured through Residual Feed Consumption (RFC). The research results serve as an important tool for beef cattle producers, breeders and researchers who use these efficiency and diet type tests to select better animals, showing the types of variations that can exist in diets, how to measure them and their influence on consumption and animal performance.