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Docility EPD: A Tool for Temperament Devori W. Beckman Iowa State University 2007 NBCEC Brown Bagger Series October 24, 2007
What is Docility? • Temperament – reaction of beef cattle to handling by humans (Burrow, 1997) • Why Measure Docility? • Ease of Handling • ADG • Carcass Quality • RFI
Measuring Docility • Flight Speed/Time, Exit Velocity • Pen Score, Docility Test, Separation Test • Chute/Crush Score
Scoring System Docile Aggressive BIF Guidelines (2002)
Docility EPD: Breed Associations • North American Limousin Foundation (NALF) • 1st Genetic Evaluation in 1998 • Scores allocated at weaning • Threshold (1, 2, 3-6); h2 = 0.40 • American Angus Association (AAA) • Genetic Evaluation Spring 2008 • Scores allocated at yearling • Threshold (1, 2, 3, 4-6); h2 = 0.37 Kuehn et al. (1998); Hyde (2003); Northcutt (2007)
Maternal (M) Effects on Docility Sire by Herd (SH) Effects Further Investigation of M and SH Effects Genetic Parameter Estimates For Docility In Limousin Cattle
Recent Work: Maternal Effects Beckman et al. (2007)
Recent Work: Sire × Herd Notter et al. (1992); CSU - Unpublished Data
Objective • Do Maternal or SH effects appropriately describe docility, or are they artifacts of the nature of this data.
Previous Models Assumed Homogeneity Beckman et al. (2007)
Assessment of Heterogeneity • Step 1: Mixed Model (BASE) Analysis
Assessment of Heterogeneity • Step 2: Fixed Model
Results: Fixed Model Beckman and Garrick (2007)
Variance Component Estimation • Mixed Model (RESID) Analysis |ê| = Xb + ZDuD + ZMuM + ZSHuSH + e
Results: Variance Components Beckman and Garrick (2007)
Conclusions • Maternal and SH Interaction Effects were Artifacts of the Data • Most of Heterogeneity Due to Herd Effects
Implications • Accuracy of Genetic Evaluation • Total Herd Reporting Garrick and Van Vleck (1987)
What’s Next? • Further Investigation of Heterogeneity • Clustering of Herds
Acknowledgements • North American Limousin Foundation • American Angus Association • Colorado State University • Iowa State University Thank you!