1. Work Toward Genetic Improvement of Disposition in Beef Cattle
R. L. Weaber, Ph.D.
Division of Animal Science
University of Missouri-Columbia

2. Why Improve Disposition?
Poor disposition creates dangerous settings for:
Animals
Workers
Increased wear and tear on facilities and equipment
Interaction between disposition (fearfulness) and production traits
Gain, feed intake, marbling, tenderness
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Fall 2006 NBCEC Brown Baggeer

3. Fall 2006 NBCEC Brown Baggeer
Phenotypic Measures
Subjective measures of disposition:
Chute Score (1-6)
Pen Score (1-5)
Objective Measures
Flight Time
Exit Velocity (m/sec)
11/09/06
Fall 2006 NBCEC Brown Baggeer

4. Fall 2006 NBCEC Brown Baggeer
Is it heritable?
Chute Score h2 =
Pen score h2 = 0.35
Exit Velocity
single measure h2 = 0.35
Avg. of two or more measures h2 =
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Fall 2006 NBCEC Brown Baggeer

5. Genetic Correlations :
Trait Correlation w/ Flight Time
Carcass Wt
Retail Yield
Marbling
Shear Force
Meat Color
(Burrow, 2003)
11/09/06
Fall 2006 NBCEC Brown Baggeer

6. NALF Docility Genetic Evaluation
First published in 1998
Heritability = 0.40
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Fall 2006 NBCEC Brown Baggeer

7. Mizzou Research Objectives
Establish relationship between disposition and production traits
Evaluation of subjective and objective measures of disposition
Investigate relationship of serial measures of disposition
Estimate genetic relationships between measures of disposition and production traits
Produce genetic evaluation for selection at MO-AES
11/09/06
Fall 2006 NBCEC Brown Baggeer

8. Fall 2006 NBCEC Brown Baggeer
Materials and Methods
111 Spring Born Angus Cross Steers
Known Pedigree
MFA Health Track Program
Disposition
Pen Score (PS)
1=Gentle, 5=Aggressive
Exit Velocity (EV)
ft/sec
Weight Gain
Back-grounding period - 55 days post-weaning
Diet included self-fed concentrate and improved fescue pastures
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Fall 2006 NBCEC Brown Baggeer

9. Fall 2006 NBCEC Brown Baggeer
Exit Velocity
Infrared Eye
Infrared Eye
6 ft
6 ft
Chute
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Data-Distribution
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Data-Distribution
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Data Analysis
Fixed Effects
Pen Score
Exit Velocity
Random Effect
Sire
Full Model (EV, PS, Sire)
EV only significant source of variation (P < 0.05)
Faster flight times were negatively associated with weight gain
Reduced Model (EV, Sire)
EV and Sire both significant (P < 0.05)
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Fall 2006 NBCEC Brown Baggeer

13. Fall 2006 NBCEC Brown Baggeer
Results-Linear Model
Steers with faster EV gained less
± 4.7 lb/sec (-5.39 ± 2.13 kg/sec)
11/09/06
Fall 2006 NBCEC Brown Baggeer

14. Results-Correlations
Correlation-a measure of linear relationship between two variables.
All P < 0.05
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Fall 2006 NBCEC Brown Baggeer

15. Results-Correlations
Correlations between serial exit velocity measures when cattle went on-feed and pen-score
All P < 0.05
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Fall 2006 NBCEC Brown Baggeer

16. Fall 2006 NBCEC Brown Baggeer
Future
330 head of MFA steers
All weight gain and carcass data collected
2/3 have individual feed intake measured
Establish relationship between disposition, efficiency, gain and carcass merit
Various hormone profiles
Genetic evaluation of disposition using EV and PS
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Fall 2006 NBCEC Brown Baggeer

17. Fall 2006 NBCEC Brown Baggeer
Questions
Thank You!
11/09/06
Fall 2006 NBCEC Brown Baggeer