Abstract
Simple SummaryBone strength in long bones is dependent on the strain it is exposed to via the forces from locomotion and bodyweight. The two strategies to increase bone strength (and reduce strain) are increasing either bone size or bone density. However, puberty initiates growth plate closure and, after puberty, most bone growth ceases. In many species, sex and age affect the relationship between bone strength and liveweight. The aim of this study was to examine how bone strength in two different limb bones was affected by age and sex in beef-cross-dairy cattle. The metacarpus and humerus was collected at time of slaughter and scanned using a peripheral quantitative computed tomography (pQCT) scanner to obtain measures of bone size and morphology from three cohorts of beef-cross-dairy cattle. Age, sex and live weight were also recorded. Live weight was the main predictor of bone size and strength, but age and sex influenced this relationship. This was reflected in heifers having a metacarpus that was shorter with less cross-sectional area and bone content than steers of the same liveweight and limited differences between steers and bulls of the same liveweight. At the same bone size older animals were heavier demonstrating an effect of age on bone maturity.In cattle, limited data have been reported about the relationship between live weight, bone size, and strength and how this relationship can be altered by factors such as sex and age. The aim of this study was to describe the relationship of peripheral quantitative computed tomography (pQCT)-derived parameters of bone strength and morphology with live weight, age and sex in beef-cross-dairy cattle. All animals were weighed the day before slaughter. The metacarpus and humerus were collected at slaughter and scanned at the mid-diaphysis using pQCT. Live weight was the primary explanatory variable for bone size and strength in all cohorts. However, the effect of age was significant, such that magnitude of response to liveweight was less in the 24-month-old cohort. Sex was significant within cohorts in that bulls had a shorter metacarpus than steers and heifers had a shorter metacarpus than steers at age of slaughter.
Highlights
IntroductionBone must increase in size and strength to maintain strain within physiological limits [1]
The data from the present study indicate that at 24 months the humerus was still experiencing appositional and longitudinal growth and is sensitive to changes in live weight
Differences in bone maturity meant that the rate of response in the metacarpus at 24 months to increases in live weight were less than that observed in 8–12 months
Summary
Bone must increase in size and strength to maintain strain within physiological limits [1]. The application of this theory has been supported by research looking in to the relationship between bone and strain where increases in live weight or loading result in a rise in bone strength [2,3]. The mid-diaphyseal site of long bones must resist the bending and torsion arising from locomotion, so increases in live weight and loading forces must result in an increase in strength [2]. The ability for bone to increase strength via appositional growth is limited once the animal attains puberty and there is a reduction in longitudinal growth when the growth plate is closed at bone maturity [5]
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