Cattle Lameness Conference 2017
The 2017 Cattle Lameness Conference was held on Wednesday 26 April 2017 at Sixways Stadium in Worcester. Reuben Newsome spoke about the role of the digital cushion in claw horn lameness, which was a focus of his PhD at the University of Nottingham.
The digital cushion sits within the hoof, beneath the pedal bone. It contains pads of fat to help cushion and dissipate forces through the foot, reducing the forces on the soft tissues that produce the sole horn. Trauma to these tissues leads to the development of claw horn lesions: sole ulcer, sole haemorrhage and white line disease, and recent work has suggested that thinner cows have thinner digital cushions, perhaps increasing the risk of lesion formation.
During his PhD, Reuben and colleagues carried out a longitudinal study of the digital cushion to explore whether the digital cushion became thinner with body condition loss, predisposing cows to lameness.
The study repeatedly measured the digital cushion of 180 cows throughout lactation using ultrasonography – once at eight weeks before calving and four times during lactation – and assessed how thickness of the digital cushion influenced the likelihood of lameness later in lactation. The digital cushion became thinner with body condition loss, but to a reasonably small extent, and many other factors also influenced thickness of the digital cushion. For example, the digital cushion was thinnest when measured within a week of calving. This is likely to have been a result of hormones around calving relaxing the suspensory apparatus of the foot, causing the pedal bone to sit lower in the hoof capsule and placing more load through the digital cushion; i.e. the digital cushion appeared thinner and had to bear more weight around calving.
Having a thin digital cushion at any point during the study strongly increased the likelihood of lameness (measured at fortnightly mobility scores) and of a claw horn lesion developing. The digital cushion could have been thin due to the cow having poor body condition, being near calving, or because of differences in genetics and rearing systems (shown to have effects in other works).
This study therefore highlights the importance of managing energy balance and providing optimal care around calving, whether this is through reducing forces on the foot from flooring surfaces or as a result of social competition; these factors reduce the forces on the soft tissues that produce the sole horn, which contribute to claw horn lesions developing.
Additionally, the digital cushion study found evidence of swelling in the digital cushion and in the surrounding tissues when a sole ulcer was present, and even before it appeared on the surface of the sole. This swelling is likely associated with lasting damage within the foot, and highlights the importance of detecting lameness and treating it early, in order to prevent further lameness.
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