Insights into the pathogenesis of catastrophic spontaneous humeral fractures in first-lactation dairy cows

Spontaneous humeral fractures in first-lactation dairy cows have introduced significant challenges to the dairy industry in New Zealand, impacting animal welfare, farm economics, and veterinary practices. This review synthesizes current knowledge on the pathogenesis of these fractures and identifies potential key risk factors. The majority of bones from affected first-lactation dairy cows have osteoporosis, which is associated with inadequate bone formation and increased bone resorption. In addition, low total collagen content in bones from most affected dairy cows supports the hypothesis that inadequate bone formation is an important risk factor associated with humeral fractures in these cows. Spectroscopic analyses further confirmed a significant reduction in bone quality and strength. Novel findings suggest that low liver copper concentration in many of the affected cows’ results from the mobilisation of copper to the bone. Although limited, the accumulated evidence suggests that to mitigate the incidence of catastrophic fractures, adequate nutrition (especially protein-energy) should be supplied during important growth periods. While significant progress has been made in understanding the cause of these fractures, many uncertainties and areas requiring further research remain.