Vasse rj sep 13v2
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Transcript of Vasse rj sep 13v2
![Page 1: Vasse rj sep 13v2](https://reader034.fdocuments.us/reader034/viewer/2022052508/559887601a28ab4f398b45ca/html5/thumbnails/1.jpg)
Muscling & eating quality
Peter McGilchrist, Kirsty Thomson,
Graham Gardner, Dave Pethick
Robin Jacob
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Selection for Muscling
•Feed efficiency
•Dressing percentage
•Saleable meat yield
Muscling desirable because
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Could selection for muscling affect meat quality?
Meat quality
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MSA grading
pHu = 5.5 pHu = 6.04
High pHu/dark colour-main reason for failure to grade MSA
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High pHu
Tenderness Flavour Visual Food safety MSA
ToughpH 5.7-6
Off flavours
Dark Colour score >3
Favours bacterial growth
Fail
RubberypH>6
Stays red after cooking
Poor keeping quality
Costs per carcase $50
$36M
Dry
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Muscling/pHu study
1. Abattoir data investigation
2. Muscling experiment
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• Funded by Beef CRC
• MSA grading data
• One abattoir
• Feb 2002 - Dec 2008
• Lots records -207, 041 carcases
• Is pHu associated with eye muscle area?
Abattoir data
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Eye muscle area
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EMA vs pHu
5.52
5.54
5.56
5.58
5.6
5.62
5.64
5.66
5.68
5.7
20 30 40 50 60 70 80 90
pH
(p
red
cit
ed
)
Eye Muscle Area (cm2)
•Larger loins
tend to have a
lower pHu on
average
•Lower
average pHu =
less dark
cutting
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HCW
5.52
5.54
5.56
5.58
5.6
5.62
5.64
5.66
5.68
5.7
20 30 40 50 60 70 80 90
pH
(p
red
cit
ed
)
Eye Muscle Area (cm2)
150 HSCW 250 HSCW Higher carcase weight lower pHu
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Effect across carcase weight
5.45
5.5
5.55
5.6
5.65
5.7
20 40 60 80 100 120
pH
(p
red
cit
ed
)
Eye Muscle Area (cm2)
150 HSCW 250 HSCW
350 HSCW 450 HSCWWithin each HCWBig loin low pHu
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Looks good but why?
• Large industry data set
• Lots of factors mixed together
• Muscling
• Age
• Finishing
• Other
Need more proof for muscling effect
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Muscling experiment
• Muscle fibre distribution
• Hormone sensitivity depends on fibre type
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Fibre types
More fast twitch fibres
Slow twitchIA
IntermediateIIA
Fast twitchIIX
Slow twitchIA
IntermediateIIA
Fast twitchIIX
Selection for muscling
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Hormone sensitivity
Slowtwitch
IA
IIB
Fasttwitch
IIX
Adrenaline
Insulin
Muscling
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FeedInsulin
Fill glycogen bucket
Feed
pHu <5.7
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pHu >5.7
Stress
Empty glycogen bucket
Adrenaline
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Hypotheses
1.Lower response to adrenalin
2.Greater response to insulin
3.More glycogen in muscle
Cattle selected for muscling will have:
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Adrenaline Response
0
5
10
15
20
25
30
35
0 0.5 1 1.5 2 2.5 3
Adrenaline Challenge (ug/kg Liveweight)
La
cta
te A
rea
Un
de
r C
urv
e (
mM
/20
min
)
High MuscledLow Muscled
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Insulin Sensitivity
Insu
lin S
ensi
tivi
ty
0
100
200
300
0.6 µg/kg/min 6.0 µg/kg/min
Glu
cose
In
fusi
on
Rat
e (m
l/h
r)
Insulin Infusion Rate
Low MuscledHigh Muscled
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Muscle Glycogen
1.45
1.5
1.55
1.6
1.65
1.7
High MuscledLow MuscledGly
co
ge
n C
on
cen
trati
on
(g
/100
g)
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Hypotheses
1.Lower response to adrenalin
2.Greater response to insulin
3.More glycogen in muscle
Cattle selected visually for muscling will have:
Now have proof
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Overall conclusion
Muscling+ Yield
+ Glycogen
Muscling experiment
Hormone responseLess adrenalineMore insulin More glycogen
Abattoir data
pHu correlated with EMALarge loin low pHu
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Acknowledgements
Dr Graham GardnerProfessor David Pethick
Dr Paul GreenwoodDr Kirstie Thomson
CRC for Beef Genetic TechnologiesMurdoch University