Claw

Abstract: This paper studies slide-resisting forces generated by claws in the free-walking beetle Pachnoda marginata (Coleoptera, Scarabaeoidea) with emphasis on the relationship between the dimension of the claw tip and the substrate texture. To evaluate the force range by which the claw can interact with a substrate, forces generated by the freely moving legs were measured using a load cell force transducer. To obtain information about material properties of the claw, its mechanical strength was tested in a fracture experiment, and the internal structure of the fractured claw material was studied by scanning electron microscopy. The bending stress of the claw was evaluated as 143.4-684.2 MPa, depending on the cross-section model selected. Data from these different approaches led us to propose a model explaining the saturation of friction force with increased texture roughness. The forces are determined by the relative size of the surface roughness R(a) (or an average particle diameter) and the diameter of the claw tip. When surface roughness is much bigger than the claw tip diameter, the beetle can grasp surface irregularities and generate a high degree of attachment due to mechanical interlocking with substrate texture. When R(a) is lower than or comparable to the claw tip diameter, the frictional properties of the contact between claw and substrate particles play a key role in the generation of the friction force.

Abstract: Summary The locomotion of 15 heifers was examined at fortnightly intervals over a 4 month peri-partum period.Measurements were made of the development of gait abnormalities, thermal and mechanical nociceptive thresholds, and severity and size of sole lesions observed in the hind claws. All heifers developed lesions at, or shortly after, parturition, and in seven animals this induced marked lameness. Abnormalities of gait were related more to the severity than to the size of the lesion. Lameness was associated with a significant increase in sensitivity to mechanical noxious stimuli applied to the lame leg but not to a thermal stimulus applied to the ear. This study demonstrated interactions between lameness, claw lesions and the development of hyperalgesia in heifers during the post-partum period.

Abstract: Objective—To examine the relationship between lameness and the duration of the interval from calving to subsequent conception in lactating dairy cows. Design—Cohort study. Animals—837 dairy cows. Procedure—Cows affected with lameness were classified into 1 of 4 groups on the basis of types of disease or lesions observed, including foot rot, papillomatous digital dermatitis, claw lesions, or multiple lesions. Cows not affected with lameness were classified as healthy. Time from calving to conception was compared between lame cows and healthy cows. Results—254 (30%) cows were affected with lameness during lactation. Most lame cows (59%) had claw lesions. Lame cows with claw lesions were 0.52 times as likely to conceive as healthy cows. Median time to conception was 40 days longer in lame cows with claw lesions, compared with healthy cows. Number of breedings per conception for lame cows with claw lesions was significantly higher than that for healthy cows. Conclusion and Clinical Relevance—Claw lesions were...