Statistical analyses
The general linear model (GLM) procedure of the
Statistical Analysis Systems Institute (SAS, 2002) was used
to test the significance of fixed effects, covariates and any
possible interactions among factors. Pearson correlation
coefficients between traits were calculated using the PROC
CORR procedure. Variance-covariance components and
standard error were obtained through the Restricted
Maximum Likelihood procedures of WOMBAT and SAS
program version 9.0. The model used accounted for random
direct genetic, common environmental litter and maternal
genetic effects. In matrix form, the model is:
ijk i j ijk ijk y μ f S (Day)β e
where Yijk is the vector of observations of the traits, μ is
the overall mean, fi is the ith farm effect, Sj is the jth sex
effect, β is the regression coefficient of slaughter day (Day),
eijk is the random error. All fixed factors included in the
model were significant (p>0.05) based on the GLM analysis.
Heritability was calculated as the ratio of animal genetic
variance to the sum of additive genetic, common
environment, and residual variances. Three generations of
pedigree information comprising 5,869 animals from
January 2007 to June 2012 were included in the analysis.
Genetic and phenotypic correlations were estimated using a
multi-trait model. All traits were analyzed together in one
Statistical analysesThe general linear model (GLM) procedure of theStatistical Analysis Systems Institute (SAS, 2002) was usedto test the significance of fixed effects, covariates and anypossible interactions among factors. Pearson correlationcoefficients between traits were calculated using the PROCCORR procedure. Variance-covariance components andstandard error were obtained through the RestrictedMaximum Likelihood procedures of WOMBAT and SASprogram version 9.0. The model used accounted for randomdirect genetic, common environmental litter and maternalgenetic effects. In matrix form, the model is:ijk i j ijk ijk y μ f S (Day)β ewhere Yijk is the vector of observations of the traits, μ isthe overall mean, fi is the ith farm effect, Sj is the jth sexeffect, β is the regression coefficient of slaughter day (Day),eijk is the random error. All fixed factors included in themodel were significant (p>0.05) based on the GLM analysis.Heritability was calculated as the ratio of animal geneticvariance to the sum of additive genetic, commonenvironment, and residual variances. Three generations ofpedigree information comprising 5,869 animals fromJanuary 2007 to June 2012 were included in the analysis.Genetic and phenotypic correlations were estimated using amulti-trait model. All traits were analyzed together in one
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