Work Toward Genetic Improvement of Disposition in Beef Cattle

1. Work Toward Genetic Improvement of Disposition in Beef Cattle R. L. Weaber, Ph.D.WeaberR@missouri.edu 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 Fall 2006 NBCEC Brown Baggeer

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

4. 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 Fall 2006 NBCEC Brown Baggeer

5. 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) Fall 2006 NBCEC Brown Baggeer

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

8. 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 Fall 2006 NBCEC Brown Baggeer

9. Exit Velocity Infrared Eye Infrared Eye 6 ft 6 ft Chute Fall 2006 NBCEC Brown Baggeer

10. Data-Distribution Fall 2006 NBCEC Brown Baggeer

11. Data-Distribution Fall 2006 NBCEC Brown Baggeer

12. 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) Fall 2006 NBCEC Brown Baggeer

13. Results-Linear Model • Steers with faster EV gained less -11.88 ± 4.7 lb/sec (-5.39 ± 2.13 kg/sec) Fall 2006 NBCEC Brown Baggeer

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

16. 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 Fall 2006 NBCEC Brown Baggeer

17. Questions Thank You! Fall 2006 NBCEC Brown Baggeer