dr. tom crenshaw - swine lamness and clinical diagnosis of skeletal integrity
TRANSCRIPT
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Clinical diagnosis of
skeletal integrity in swine
TD Crenshaw, JL Reichert, JR Booth, DK Schneider, and LA Rortvedt-Amundson
Department of Animal Sciences
University of Wisconsin
Madison, WisconsinSRTC
Swine Research &
Teaching Center
2013 Allen D. Leman Swine Conference
September 17, 2013 – St. Paul, Minnesota
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Bone- what you hitch muscle to!
4-H youth definition
Bone is more than a stick.
Loveridge, 1999. J Anim Sci 77:190-196
Bone as an endocrine organ.
Fukumoto and Martin, 2009.
Trends Endoc. Metab. 20:230-236
Advances in our understanding of
the functional role of bone
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Skeletal Lameness in Swine
Mineralization Osteochondrosis
Carlson et al., 2010
What’s the problem Doc?
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Bone Callous – “beaded-ribs” in a growing pig fed a diet with marginal Ca and P
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Bones must not only carry the animal to market –but also through the fabrication processes
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Bone Composition
Ca & P content in bone ash constant ratio = 2.1:1
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Osteon
Growth plateMidshaft section
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Methods to assess skeletal tissues responses to nutrient inputs
Method Test Prospects Pitfall
Histology Terminal Dynamic Sample size/time
Gravimetric Terminal Standard Accuracy DXA
Non-invasive Whole animal Ash ≠ Strength
Mechanical Terminal Structural Irregular shape &
Integrity composite material
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Calculations:
Predicted BMC from initial pig weight
pBMC0 = 24.1 + 14.1*BW
Bone Mineral Content Gain
BMCg, g/d = (BMC56 – pBMC0)/56
Ca retention, g/d = (BMCg * 0.38)/0.964
P retention, g/d = (BMCg * 0.18)/0.80
Ca efficiency = Ca retention / Ca intake
P efficiency = P retention/ P intake
GE Lunar Prodigy DXA – scan of ~ 60 kg pig
0 200 400 600 800 1000 1200 1400
Dissected Bone Ash, g
0
200
400
600
800
1000
1200
1400
Ash, g
Small Animal
Adult, standard
Adult, thick
Selected Scan Modes
BMC = 3.3 + 1.001 Ash, R 2 = 0.99
GE Lunar Prodigy DXA – Improved speed and accuracy
Ash content accurately predicted with selected modes:
Small animal, < 20 kg
Adult Standard, 20 to 46 kg
Adult Thick, > 46 kg
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DepletionPeriod
RecoveryPeriod
150%NRC Ca
70%NRC Ca
150%NRC Ca
70%NRC Ca
Days 0 to 28
Days 28 to 71
Recovery of Skeletal Mineral after a Period
of Calcium Depletion
Experimental Design
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Recovery from Ca Depletion
Total Skeletal Growth and Mineralization
In Recovery:
Skeletal Mass not affected by prior depletion
Skeletal Mineralization tended to “Catch-up”
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DXA scans of the pig footDoes foot orientation affect accuracy?
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Identify the threshold value for a
deficiency based on percent bone ash
?Variables
that affect the decision
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Response to diets vary among bones and age
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Percent ash varies with age and bones in pigs fed adequate diets
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Decrease in % ash with age
related to failure of mineral
accretion to keep pace with the
rapid growth of organic matrix.
Vanderwerff et al., 2013
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Carry-over of maternal vitamin D on nursery pigs
Rortvedt-Amundson et al., 2013
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Whole Body DXA: Birth and Weaning
Differences among maternal diets were not detected in pig
BMD at birth or weaning
19Rortvedt-Amundson et al., 2013
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Whole Body DXA: End of Nursery
0 325 1750
Sow diet, IU D3/kg
BMD reduced 25% in pigs produced by gilts fed 0 vs 325 and 1750 IU D3/kg.
Pigs fed –D120P nursery diets had reduced BMD if produced by gilts fed 0 or 325
IU D3/kg, but not 1750 IU D3/kg
20Rortvedt-Amundson et al., 2013
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Unexpectedly, with 0 supplemental vitamin D, femur stress increased >20% if pigs were fed diets with 150% Ca & 120% P requirement.
Rortvedt-Amundson et al., 2013
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Femur vs Fibula
“which bone is best”
Femur Fibula
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Femur vs Fibula “which bone is best”
Both have similar “fits” to P intake (R2)
Femur has steeper slope than Fibula (more sensitive response to P intake)
Femur Fibula
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Femur ash as a predictor of whole body skeletal ash
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Fibula ash as a predictor of whole body skeletal ash
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Femurs vs Fibulas as Predictors of Whole Body Bone Mineral Content
Conclusions
DXA accurately predicts whole body BMC (g ash/pig)
Fibulas over estimate BMC at low P intakes but under estimate BMC at high P intakes
Femurs accurately predict BMC over a range of P intakes
Femurs offer a more accurate assessment of BMC than fibulas in young growing pigs
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Which bone better predicts Pig BMC at market weight?
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Development of standards for
DXA femur scans
DXA scores for femurs ~ same in pigs with lameness
DXA femur scans – pigs with lameness
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Development of standards for
DXA feet scans
DXA feet scans – pigs with lameness
DXA scores for feet slightly lower in pigs with lameness
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Stick to the facts
Start earlyStudy the records carefully
Support co-workers
Share information
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?Variables
that affect the decision
Conclusions
Accurate measures of bone ash can be rapidly completed with DXA
scans of whole pigs or individual bones.
Femurs are better predictors of whole body bone mineral content than
fibulae or feet
Percent bone ash is not a sensitive indicator of mineral adequacy
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Acknowledgements
Cargill/Benevenga Undergraduate Research Stipend
UW SRTC staff & students
Swine Research
& Teaching Center