A study in the aetiopathogenesis of claw horn disruption lesions in dairy cattle

Claw horn disruption lesions (CHDL) are the main non-infectious cause of lameness in dairy cattle worldwide. Lameness is both prevalent and associated with a vast array of significant negative effects. Sole ulcers, sole haemorrhage (jointly termed sole lesions; SL), and white line disease (WLD) are collectively called CHDL. This thesis aimed to explore the aetiopathogenesis of CHDL. A cohort of 2,352 Holstein cows were prospectively enrolled from four commercial UK dairy farms as part of a longitudinal study. Cows were examined at four key time points in the production cycle. Data collected included detailed foot lesion records, digital cushion thickness (DCT), sole horn thickness (SHT), body condition score (BCS), back fat thickness (BFT), and sole temperature (ST). Additionally, serum and plasma blood samples were collected at all time points. In a subset of 200 cows, serum concentrations of ß-hydroxybutyrate, non-esterified fatty acids, relaxin, insulin, interleukin-1α, interleukin-6 and interleukin-10, and plasma lipopolysaccharide concentrations were measured. Parity and calving dates were obtained from farm records. Analyses highlighted the importance of the digital cushion and SHT in SL development but not WLD development. Foot angle and heel depth were not associated with the development of CHDL; however, ST was associated. Interactions were present between SHT and the presence of a SL prior to calving, ST prior to calving and parity, and DCT prior to calving and parity. Farm and stage of lactation were both associated with the DCT; however, an interaction was present and this DCT pattern of change was farm dependent. Neither BCS nor BFT were associated with the DCT. Parity was associated with the DCT and an interaction with stage of lactation was present. Sole lesions and WLD at the time of measurement were associated with the DCT. The importance of inflammation during the periparturient period was confirmed and the role of negative energy balance during this same period was highlighted. The role of relaxin in the development of SL was not confirmed. A technique for laminar corium biopsies was described in healthy lactating cattle with and without CHDL. Transient lameness was observed post-biopsy; however, no permanent hoof damage was recorded. This thesis has advanced our understanding of the aetiopathogenesis of CHDL. Providing adequate SHT prior to and shortly after calving was highlighted as being significant in the development of SL. The importance of the DCT has been confirmed, and different farm and management factors affect how the DCT changes throughout the production cycle. Inflammation has been confirmed as being of importance, and this could be influenced by the metabolic status of cows at calving. Relaxin was not associated with the development of CHDL and further investigations of the calving effect would be justified in analysing the roles of oestrogen or insulin-like peptide 3.