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

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 11/09/06 Fall 2006 NBCEC Brown Baggeer

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

Fall 2006 NBCEC Brown Baggeer 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 11/09/06 Fall 2006 NBCEC Brown Baggeer

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) 11/09/06 Fall 2006 NBCEC Brown Baggeer

NALF Docility Genetic Evaluation First published in 1998 Heritability = 0.40 11/09/06 Fall 2006 NBCEC Brown Baggeer

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

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 11/09/06 Fall 2006 NBCEC Brown Baggeer

Fall 2006 NBCEC Brown Baggeer Exit Velocity Infrared Eye Infrared Eye 6 ft 6 ft Chute 11/09/06 Fall 2006 NBCEC Brown Baggeer

Fall 2006 NBCEC Brown Baggeer Data-Distribution 11/09/06 Fall 2006 NBCEC Brown Baggeer

Fall 2006 NBCEC Brown Baggeer Data-Distribution 11/09/06 Fall 2006 NBCEC Brown Baggeer

Fall 2006 NBCEC Brown Baggeer 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) 11/09/06 Fall 2006 NBCEC Brown Baggeer

Fall 2006 NBCEC Brown Baggeer Results-Linear Model Steers with faster EV gained less -11.88 ± 4.7 lb/sec (-5.39 ± 2.13 kg/sec) 11/09/06 Fall 2006 NBCEC Brown Baggeer

Results-Correlations Correlation-a measure of linear relationship between two variables. All P < 0.05 11/09/06 Fall 2006 NBCEC Brown Baggeer

Results-Correlations Correlations between serial exit velocity measures when cattle went on-feed and pen-score All P < 0.05 11/09/06 Fall 2006 NBCEC Brown Baggeer

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 11/09/06 Fall 2006 NBCEC Brown Baggeer

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