Introduction
Softening of connective tissue of the claw suspensory apparatus around calving as described by Tarlton, et al. (2002) may lead to sinking of the bovine pedal bone resulting in compression of the digital cushion. The objective of this study was to describe changes in the thickness of the soft tissue on weight bearing claws in the weeks around calving. 
Materials and methods
Thirty‐five Holstein heifers were followed in a Danish dairy herd. Each heifer underwent an ultrasonographic examination of the hind claws four times,twice before calving and twice after calving, with a one‐week interval. The ultrasonographic examination was performed through the sole horn as described in other studies (Bicalho, et al. 2009, Kofler, et al. 1999, van Amstel, et al. 2004)
but on weight bearing claws, while the heifers were standing in a tub with a 10 mm. thick polyethylene bottom. The claws were covered with water to improve the image quality. At each examination, the body condition score (BCS) of the heifers was recorded. The thickness of the soft tissue in the sole, defined as the distance between inner margin of the sole horn and the pedal bone, was measured on the ultrasonographic images at the apex of the claw and at the typical sole ulcer site.

Results
We made 1096 ultrasonographic examinations. Figure 1. Thickness of the soft tissue in millimeter at the sole ulcer site (grey boxes) and at the apex
of the claw (white boxes) in the weeks around calving. “‐2” and “‐1” is week two and one before calving respectively. “1” and “2” is the first and second week after calving. The mean thickness of the soft tissues at the typical sole ulcer site was reduced with 0.6 millimeters from the first to the last examination (Figure 1). This was a 15 % reduction of the thickness, in approximately four weeks. The
correlation between “days from calving” and “thickness of the soft tissue” was 0.31 (Pearson’s, p<0.001). At the apex of the claw only small changes was observed. We did not observe any significantly loss in BCS in the four‐week period we followed the heifers’.176

Discussion
The decrease in soft tissue thickness in the weeks post‐partum could be the result of actual sinking of the pedal bone inside the claw capsule. This may lead to increased pressure on the dermis of the sole horn. However, we do not know if the decrease in thickness entirely was a consequence of calving. Changes in environment, feeding and handling of the heifers might also contribute to the decrease in the thickness and development horn related lesions as described by other authors (Bergsten, et al.2015, Webster 2001) In future studies, multiparous cows and animals from more than a single farm should be included and the number of known risk factors related to claw horn lesions should be limited. A longer