There is a tendency, in some orders of mammals, to increase the number of thoracolumbar vertebrae. In pigs, the appearance of additional vertebrae is a criterion of commercial selection that managed to increase meat production. In sheep the number of extra vertebrae has been little studied and only in some breeds, but the results point in the same direction. The objective was to determine if there is variation between the number of lumbar vertebrae and its effect on the length and volume of the lumbar region, depth of muscle and fat tissue in Suffolk ewes nucleus herd. A total of 169 lambs were used, which were evaluated with X-rays, the number of vertebrae in the lumbar area and their length, with ultrasound, the depth of the spine and fat cover. Variation was observed in the number of lumbar vertebrae, where 5L (30.8%) and 6L (67.5%) were the most frequent and 7L (1.8%) the lowest. As the lumbar vertebral formula increased, each vertebra decreased in size but together they increased the lumbar length from 230.4 mm for 5L to 316.7 mm for 7L, and their volume from 130.1 to 181.0 cm3, respectively, and was associated with a slight increase in the depth of the loin and its covering fat. With this, Suffolk sheep, with extra vertebrae, showed greater length and volume in the lumbar area.