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Claw lesions are the third most important health issue in dairy cattle, after mastitis and reproductive disorders, and genomic selection is a key component for long-term improvement of claw health. The objectives of this study were to assess the feasibility of a genomic evaluation for claw health in French Holstein cows, explore possibilities to increase evaluation accuracy, and gain a better understanding of the genetic determinism of claw health traits. The data set consisted of 48,685 trimmed Holstein cows, including 9,646 that were genotyped; 478 genotyped sires were also used. Seven claw lesion traits were evaluated using BLUP, genomic BLUP, BayesC, and single-step genomic BLUP, and the accuracies obtained using these approaches were measured through a validation study. The BayesC approach was used to detect quantitative trait locus (QTL) regions associated with the 7 individual traits (digital dermatitis, heel horn erosion, interdigital hyperplasia, sole hemorrhage circumscribed, sole hemorrhage diffused, sole ulcer, and white line fissure) based on their Bayes factor. Annotated genes on these regions were reported. Genomic evaluation approaches generally did not allow for greater accuracies than BLUP, except for single-step genomic BLUP. Accuracies were moderate, but best and worst validation animals were correctly discriminated and showed significant differences in lesion frequencies. A total of 192 QTL regions were identified, including 13 with major evidence or involved for 2 of the traits. A high number of genes were present on these regions, and several had functions associated with the immune system. In particular, the EPYC gene is located close to a major evidence QTL for resistance to digital dermatitis that is also a QTL for interdigital hyperplasia (on chromosome 5, around 20.9 MB) and has been associated with Ehlers-Danlos syndrome in cattle. Genomic selection can be used to improve resistance to individual claw lesions, and several possibilities exist to improve accuracies of genomic evaluations., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Claw horn disruptions in the bovine claw are believed to be a consequence of pressure on the sole corium from the third phalanx, which may be caused by a weakening of the suspensory apparatus in the claw. We aimed to develop an ultrasonographic method that would make it possible to measure the thickness of the soft tissue between the third phalanx and the sole horn on a weight-bearing claw. A device was developed to record the sole horn and soft tissue thickness indirectly through a polyethylene plate, and 52 feet from slaughtered cows were examined using ultrasonography, both directly and indirectly. Soft tissue and sole horn thickness measurements in the apex and the plantar part of the sole were compared with anatomical measurements of transected claws. To assess the method on weight-bearing versus non-weight-bearing claws, we examined the hind claws of 10 live cattle without transection. We found a weak correlation between the soft tissue thickness measured by ultrasound and anatomical measurements. A strong correlation was observed between the direct ultrasound approach and the developed indirect method. There was a considerable difference between weight-bearing and non-weight-bearing claws, signifying a weak or nonexistent correlation. However, this part of the study was only done on 10 live cows and the results should be interpreted with caution. We concluded that it would be possible to measure the soft tissue using an indirect ultrasound approach on a weight-bearing-claw standing on a polyethylene plate. The major difference between the results of weight-bearing versus non-weight-bearing claws suggests that future studies of the suspensory apparatus could focus on weight-bearing claws., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Lameness causes major financial losses and welfare problems in dairy herds. Prevention of foot lesions may suffice in the majority of lameness cases. The objectives of this longitudinal study were to describe the dynamics and associations between abnormal hind leg conformation, asymmetric claws, lameness, and foot lesions in 122 Danish Holstein heifers from an average of 41 d before first calving until dry off or culling. The cattle were housed either in a free-stall system with cubicles or in deep-bedded straw yard. The claws of all cattle were examined on up to 5 occasions. The associations between foot lesions, lameness, symmetry of the claws, shape of the dorsal toe-wall, and the conformation of the hind legs were examined statistically using mixed models. A large proportion (81%) of the heifers had cow-hocked conformation, with wide-based stance, hocks together, and lateral rotation of the foot before calving, and 25% of the heifers had locomotion scores above 2, indicating signs of lameness, before calving. Our results indicate that lameness, abnormal conformation, and lesions acquired precalving persist throughout the first lactation. Thinner cows were more cow-hocked, and cow-hocked cows had a higher frequency of sole hemorrhages. Increased severity of white line lesion was associated with greater claw asymmetry. More severe lameness and sole hemorrhages were found in symmetric claws.

Pathological claw formations occur subsequent to irregular or prolonged claw trimming periods and as a result of improper flooring. Clinical experience and material testing finds horn of minor quality to be associated with the malformations. Finite element models (FEM) of a flat claw (FC), a contracted claw (CC), and a laminitic claw (LC) were designed from native claw specimens to combine material properties and altered claw geometry for stress analysis. The FEM were created by digitizing the typically deformed exungulated claw capsule by means of computed tomography or digital photography. The derived geometry data were meshed with finite elements and the material properties were attributed. Loading was performed via vertical load vectors according to the suspensory and support apparatus of the bovine digit. All FEM were loaded on soft floors. Loading of the FEM of the FC with 756 N exhibited maximum stress values of 3.32 MPa in the dorsal wall, that of the CC exhibited comparably lower stress of 1.33 MPa in the distal abaxial wall, and the model of the LC showed maximum stress of 4.51 MPa in the region of the dorsal border, all at the same loading. The solar surfaces and the corresponding imprints showed stress concentrations in the palmar aspect of the bulb in the FC, a highly stressed bearing margin of the abaxial wall in the CC, and a diffusely stressed sole and bulb in the LC in contrast to the sound claw models. The FEM of the selected pathological claw forms (FC, CC, LC) calculated high stress zones exactly at locations in the claw wall and sole where clinical experts expect the typical claw lesions for these pathologies. These results were obtained simply by exchanging the outer form of the claw capsules; the method of loading and type of flooring for these pathological models were equivalent to those of the sound FEM. It is highly possible that the stress zones derived from these calculations represent corium compression in reality, and these data support the pathophysiological theory that claw lesions may arise as a consequence thereof.