There are obvious phenotypic differences among beef cattle breeds, but, to date, there are limited data on the effect of breed and pasture-based management systems on the bone mass and strength of the distal limb bone (metacarpals). The left 3rd/4th metacarpal bones were collected from a cohort of Angus (AA) (n= 17), Angus × Friesian (AF) (n=13), and Angus × Jersey (AJ) (n=13) cows aged nine years at slaughter. Prior to slaughter the cohort had been intensively monitored as part of longevity- and GPS-based paddock-activity trials. Measures of metacarpal bone mass and strength were assessed using peripheral quantitative computed tomography (pQCT) scanning at the mid-diaphysis after slaughter. Locomotion parameters, based on GPS data when grazing, were collected when four and five years old. The AA and AF cows had significantly greater slaughter weight than AJ (598±14 vs 586±18 vs 514±17 kg, P<0.01 respectively). AA cows had lower wither height than AF and AJ (1288±6 vs 1311±8 vs 1269±7 mm, P<0.01) and shorter metacarpal bone length (198±2, vs 207±2 vs 210±2 mm, P<0.05). At the mid-diaphyseal site, AF and AJ cows had greater bone mineral density (BMD)v than did AA cows (977±8 vs 1018±9 vs 1019±9 mg/cm3, respectively, P<0.001), but had less cross-sectional area (882±16 vs 816±18 vs 731±18 g/cm3, P<0.05 respectively). Across all breeds, there was a negative relationship of slaughter weight with BMDv. No significant relationships were found between distance walked on moderate and steep terrain (GPS data) and the pQCT measures. Breed influenced the size and structure of the metacarpal bone, which altered the material properties (pQCT) measured. The limited amount of high-strain-rate exercise in these cattle may explain the lack of association between locomotion data and measures of bone mass and strength. Keywords: bovine; bone; GPS; locomotion; beef

L, Bijen, MJ Gibson, PJ Back, RE Hickson, A van Knegsel, and CW Rogers

Proceedings of the New Zealand Society of Animal Production, Volume 80, Online, 29-33, 2020
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