Work Toward Genetic Improvement of Disposition in Beef Cattle

R. L. Weaber, Ph.D. WeaberR@missouri.edu Division of Animal ScienceUniversity of Missouri-Columbia

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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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Phenotypic Measures

Subjective measures of disposition:– Chute Score (1-6)– Pen Score (1-5)

Objective Measures– Flight Time– Exit Velocity (m/sec)

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Is it heritable?

Chute Score h2 = 0.26-0.40 Pen score h2 = 0.35 Exit Velocity

– single measure h2 = 0.35– Avg. of two or more measures

h2 = 0.44-0.50

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Genetic Correlations :

Trait Correlation w/ Flight Time

Carcass Wt. 0.05

Retail Yield 0.11

Marbling -0.05

Shear Force -0.48

Meat Color -0.18

(Burrow, 2003)

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NALF Docility Genetic Evaluation

First published in 1998Heritability = 0.40

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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

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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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Exit Velocity

6 ft 6 ftChute

Infrared Eye

Infrared Eye

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Exit Velocity Histogram

0

5

10

15

20

25

30

35

40

3.4 4.7 6.0 7.3 8.6 9.9 11.2 12.5

Exit Velocity (ft/s)

Fre

qu

en

cy

Data-Distribution

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Data-Distribution

Pen Score Histogram

05

1015202530354045

1 2 3 4 5

Pen Score

Fre

qu

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cy

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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)

. i i i ji iWt Gain EV PS Sire e

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Results-Linear Model

Steers with faster EV gained less-11.88 ± 4.7 lb/sec (-5.39 ± 2.13 kg/sec)

EV Std. Dev (1.64 ft/s)

EV (ft/s)

Gain Gain Difference

ADG ADG Difference

-2 4.1 206.68 38.97 3.76 0.71-1 5.7 187.19 19.48 3.40 0.350 7.4 167.71 0.00 3.05 0.001 9.0 148.23 -19.48 2.70 -0.352 10.7 128.74 -38.97 2.34 -0.71

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Results-Correlations

PS EV WGPS 1.00 0.36 -0.21EV 0.36 1.00 -0.24WG -0.21 -0.24 1.00

All P < 0.05

Correlation-a measure of linear relationship between two variables.

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Results-Correlations

EV1 EV2 PS WTEV1 1.00 0.59 0.38 -0.25EV2 0.59 1.00 0.42 -0.36PS 0.38 0.42 1.00 -0.35WT -0.25 -0.36 -0.35 1.00

All P < 0.05

Correlations between serial exit velocity measures when cattle went on-feed and pen-score

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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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Questions

Thank You!