Use of robust multivariate linear mixed models for estimation of genetic parameters for carcass traits in beef cattle. (17th May 2014)

• Record Type: Journal Article
• Authors: Peters, S.O.; Kizilkaya, K.; Garrick, D.J.; Fernando, R.L.; Pollak, E.J.; Enns, R.M.; De Donato, M.; Ajayi, O.O.; Imumorin, I.G.
• Is Part Of: Journal of animal breeding and genetics. Volume 131:Number 6(2014:Dec.)
• Page Start: 504
• Page End: 512
• Publication Date: 2014-05-17
• Subjects: Livestock -- Breeding -- Periodicals; Livestock -- Genetics -- Periodicals; 636.0820
• DOI: 10.1111/jbg.12093
• Languages: English
• ISSNs: 0931-2668

Abstract

<abstract abstract-type="main" id="jbg12093-abs-0001"> <title>Summary</title> <p>Assumptions of normality of residuals for carcass evaluation may make inferences vulnerable to the presence of outliers, but heavy‐tail densities are viable alternatives to normal distributions and provide robustness against unusual or outlying observations when used to model the densities of residual effects. We compare estimates of genetic parameters by fitting multivariate <italic>Normal</italic> (MN) or heavy‐tail distributions (multivariate <italic>Student's t</italic> and multivariate <italic>Slash</italic>, MS<italic>t</italic> and MS) for residuals in data of hot carcass weight (HCW), longissimus muscle area (REA) and 12th to 13th rib fat (FAT) traits in beef cattle using 2475 records from 2007 to 2008 from a large commercial operation in Nebraska. Model comparisons using deviance information criteria (DIC) favoured MS<italic>t</italic> over MS and MN models, respectively. The posterior means (and 95% posterior probability intervals, PPI) of <italic>v</italic> for the MS<italic>t</italic> and MS models were 5.89 ± 0.90 (4.35, 7.86) and 2.04 ± 0.18 (1.70, 2.41), respectively. Smaller values of posterior densities of <italic>v</italic> for MS<italic>t</italic> and MS models confirm that the assumption of normally distributed residuals is not adequate for the analysis of the data set. Posterior mean (PM) and posterior median (PD) estimates of direct genetic variances were variable with MS<italic>t</italic> having the highest mean value followed by MS and MN, respectively. Posterior inferences on genetic variance were, however, comparable among the models for FAT. Posterior inference on additive heritabilities for HCW, REA and FAT using MN, MS<italic>t</italic> and MS models indicated similar and moderate heritability comparable with the literature. Posterior means of genetic correlations for carcass traits were variable but positive except for between REA and FAT, which showed an antagonistic relationship. We have demonstrated that genetic evaluation and selection strategies will be sensitive to the assumed model for residuals.</p> </abstract>