Osteoporosis is the cause of spontaneous humeral fracture in dairy cows from New Zealand

Abstract

Outbreaks of humeral fractures in dairy cows have been reported in New Zealand for several years. Gross, histologic, and histomorphometric findings in the humerus from primiparous cows with spontaneous humeral fracture were compared to age-matched control cows. Affected cows had a complete nonarticular spiral fracture of the humerus. Histologically affected humeri had a thicker growth plate with abnormal architecture, thinner cortex with increased abnormal resorption, increased resorption in the distal humerus, decreased trabecular density, abnormal trabecular architecture, presence of growth arrest lines and woven bone formation. Histomorphometry showed reduction in bone volume, trabecular perimeter, and trabecular width. Cows grazed on fodder beet had thicker growth plates with an abnormal appearance compared with cows grazed on pasture, and cows with low/marginal liver copper concentration had more resorption cavities in the distal humerus and thinner cortical bone compared with cows with adequate liver copper concentration. Decreased trabecular density (OR = 249.5), abnormal cortical resorption (OR = 54.2), presence of woven bone formation in the proximal metaphysis (OR = 37.2), and the number of resorption cavities in the distal humerus were significantly associated with a high probability of fracture. Ribs had enlargement of the costochondral junction with fractures in different stages of healing. Histology of the ribs revealed abnormal growth plate appearance, presence of fracture lines, callus tissue, fibrosis, and microfractures. Cows with humeral fracture have osteoporosis due to decreased bone formation and increased bone resorption, likely associated with inadequate feed quality and perhaps copper deficiency leading to a reduction in bone strength and fracture.

Bone quality changes as measured by Raman and FTIR spectroscopy in primiparous cows with humeral fracture from New Zealand

“…A lower mineral/matrix ratio is reported in iliac crest bone biopsies from women and men with high-turnover osteoporosis (defined as an increased number of resorption surfaces and higher than the normal number of osteoclasts) compared to bone biopsies samples from women and men with low-turnover osteoporosis and normal bone activity ( 16 ). These results corroborate the findings from a previous analysis done on this same set of bone samples, which found that bones from cows with humeral fractures had increased abnormal resorption of cortical bone and increased bone resorption in this distal humerus ( 4 ). Furthermore, peripheral quantitative computed tomography data has found a reduction in cortical bone mineral density in the mid-diaphysis of the humerus of fractured cows ( 3 ).…”

“…For example, histological analysis of bone samples from primiparous cows with humeral fracture determined that cows with humeral fractures developed osteoporosis characterized by decreased bone volume, abnormal trabecular architecture, presence of growth arrest lines, thinner cortex with increased resorption in the cortex and distal humerus ( 1 ). These findings were associated with periods of poor bone formation (probably due to protein-calorie undernutrition), increased bone resorption associated with lactation, and periods of copper deficiency ( 1 , 4 ). Peripheral quantitative computed tomography of the mid-diaphysis of the humerus showed that fractured animals had reduced cortical bone mineral density which reduced the stress-strain index ( 3 ).…”

Novel Assessment of Collagen and Its Crosslink Content in the Humerus from Primiparous Dairy Cows with Spontaneous Humeral Fractures Due to Osteoporosis from New Zealand

“…For the first time, we were able to measure the total collagen content and collagen crosslink content in bone from dairy cows in New Zealand which allowed us to establish important conclusions regarding the likely pathogenesis of spontaneous humeral fracture. In the case of collagen and its crosslinks, the total collagen content was significantly higher in bone from control cows and cows with adequate liver Cu concentration consistent with the histologic findings of osteoporosis reported [ 4 ]. Cows with humeral fracture and low liver Cu concentration have an increased concentration of total collagen crosslinks, DHLNL, and HYP in bone.…”

“…Another study, using peripheral quantitative computed tomography, has shown a consistent trend for reduced bone length and reduced cortical bone mineral density in primiparous cows with humeral fractures compared with age-matched controls [ 3 ]. The findings from both these studies support the hypothesis that periods of inadequate nutrition (most likely protein-calorie undernutrition) act as a contributory factor in the occurrence of humeral fractures in cows and furthermore suggest these changes are recent [ 3 , 4 ].…”

“…Since the first reported case of spontaneous humeral fracture in primiparous dairy cows in New Zealand, several risk factors have been hypothesized as associated with an increased incidence of fractures [ 1 , 2 , 3 ]. The largest histological study on humeral fractures determined that cows have osteoporosis due to inadequate bone deposition during the first months of the cow’s life and increased bone resorption in the post calving period [ 4 ]. Another study, using peripheral quantitative computed tomography, has shown a consistent trend for reduced bone length and reduced cortical bone mineral density in primiparous cows with humeral fractures compared with age-matched controls [ 3 ].…”