The aim of this research was to investigate the correlation between the thickness of solar soft tissue (SST; i.e. the corium and subcutaneous tissue) in early lactation and sole ulcer formation in late lactation. Fifty Holstein–Friesian cows were examined three times: (1) 30 days after calving (locomotion scoring, trimming, claw examination, measurement of SST); (2) 70 days after calving (locomotion scoring); and (3) 180 days after calving (locomotion scoring, trimming, claw examination).
SST thickness was measured using an 8 MHz linear probe, at two points (SST1 below the apex of the pedal bone, and SST2 below the flexor tubercle). Mean values for SST1 and SST2 were 3.26 ± 0.43 mm and 4.35 ± 0.46 mm, respectively; the two measures were positively correlated (r = 0.95, P < 0.001). At 180 days after calving, a sole ulcer was diagnosed in 12/50 cows (24%). Cows with a thinner SST had a higher risk of developing sole ulcers than those with a thicker SST. The optimal cut-off values of SST1 and SST2 in predicting cows with sole ulcers (as calculated by ROC analysis) was ⩽3 mm for SST1 and ⩽3.9 mm for SST2. The relative risk of a sole ulcer developing, based on those cut-off values was 4.25 (95 CI, 1.77–24.88) for SST1 ⩽ 3 mm and 3.63 (95 CI, 1.18–10.8) for SST2 ⩽ 3.9 mm.