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

1

2

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

Skeletal Lameness in Swine

Mineralization Osteochondrosis

Carlson et al., 2010

What’s the problem Doc?

Bone Callous – “beaded-ribs” in a growing pig fed a diet with marginal Ca and P

Bones must not only carry the animal to market –but also through the fabrication processes

Bone Composition

Ca & P content in bone ash constant ratio = 2.1:1

Osteon

Growth plateMidshaft section

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

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

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

Recovery from Ca Depletion

Total Skeletal Growth and Mineralization

In Recovery:

Skeletal Mass not affected by prior depletion

Skeletal Mineralization tended to “Catch-up”

DXA scans of the pig footDoes foot orientation affect accuracy?

Identify the threshold value for a

deficiency based on percent bone ash

?Variables

that affect the decision

Response to diets vary among bones and age

Percent ash varies with age and bones in pigs fed adequate diets

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

Carry-over of maternal vitamin D on nursery pigs

Rortvedt-Amundson et al., 2013

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

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

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

Femur vs Fibula

“which bone is best”

Femur Fibula

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

Femur ash as a predictor of whole body skeletal ash

Fibula ash as a predictor of whole body skeletal ash

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

Which bone better predicts Pig BMC at market weight?

Development of standards for

DXA femur scans

DXA scores for femurs ~ same in pigs with lameness

DXA femur scans – pigs with lameness

Development of standards for

DXA feet scans

DXA feet scans – pigs with lameness

DXA scores for feet slightly lower in pigs with lameness

Stick to the facts

Start earlyStudy the records carefully

Support co-workers

Share information

?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

Acknowledgements

Cargill/Benevenga Undergraduate Research Stipend

UW SRTC staff & students

Swine Research

& Teaching Center