Simultaneous Estimation of Variance and Covariance Components from Multitrait Mixed Model Equations

Biometrics ◽  
1978 ◽  
Vol 34 (2) ◽  
pp. 199 ◽  
Author(s):  
L. R. Schaeffer ◽  
J. W. Wilton ◽  
R. Thompson
Keyword(s):  
Mixed Model ◽  
Simultaneous Estimation ◽  
Covariance Components ◽  
Variance And Covariance Components ◽  
Model Equations ◽  
Estimation Of Variance

scholarly journals Mixed model approaches for diallel analysis based on a bio-model

1996 ◽  
Vol 68 (3) ◽  
pp. 233-240 ◽  
Author(s):  
Jun Zhu ◽  
Bruce S. Weir
Keyword(s):  
Mixed Model ◽  
Diallel Analysis ◽  
Worked Examples ◽  
Genetic Effects ◽  
Unbiased Estimation ◽  
Paternal Effects ◽  
Covariance Components ◽  
Variance And Covariance Components ◽  
Parameter Values ◽  
Estimation Of Variance

SummaryA MINQUE(l) procedure, which is minimum norm quadratic unbiased estimation (MINQUE) method with 1 for all the prior values, is suggested for estimating variance and covariance components in a bio-model for diallel crosses. Unbiasedness and efficiency of estimation were compared for MINQUE(l), restricted maximum likelihood (REML) and MINQUE(θ) which has parameter values for the prior values. MINQUE(l) is almost as efficient as MINQUE(θ) for unbiased estimation of genetic variance and covariance components. The bio-model is efficient and robust for estimating variance and covariance components for maternal and paternal effects as well as for nuclear effects. A procedure of adjusted unbiased prediction (AUP) is proposed for predicting random genetic effects in the bio-model. The jack-knife procedure is suggested for estimation of sampling variances of estimated variance and covariance components and of predicted genetic effects. Worked examples are given for estimation of variance and covariance components and for prediction of genetic merits.

PRETEST HERD EFFECTS ON STATION PERFORMANCE TEST

1986 ◽  
Vol 66 (4) ◽  
pp. 925-935 ◽  
Author(s):  
A. K. W. TONG ◽  
J. A. NEWMAN ◽  
G. W. RAHNEFELD
Keyword(s):  
Fixed Effects ◽  
Mixed Model ◽  
Performance Test ◽  
Average Daily Gain ◽  
Research Station ◽  
Environmental Correlations ◽  
Warm Up ◽  
Covariance Components ◽  
Variance And Covariance Components ◽  
Daily Gain

Effects of herd of origin and the relationships between pretest and station test environments were examined from pre- and postweaning performance records of 1675 crossbred male and female calves of Hereford, Angus and Shorthorn dams, sired by 20 Charolais, 12 Simmental and 15 Limousin sires. The calves were born during 1969–1972 and raised to weaning in 45 herds from Manitoba, Saskatchewan and Alberta, and were then transported to the Brandon or the Lacombe Research Station for a 140-d postweaning performance test. Fixed effects and variance and covariance components were estimated from a mixed model which included fixed effects of herd-year, sex of calf and breed of sire and random sire effects. Herd-year effects were significant (P < 0.01) for all performance traits studied. Herd-year mean squares expressed as a percentage of the corrected total sum of squares accounted for 25.81% in the pretest period to a maximum of 54.26% in the warm-up period and then decreased to 6.78% in the 140-d period. Herd-year differences were relatively small in the later part of the test. Correlations of herd-year solutions ranged from −0.10 to 0.05 and of environments ranged from −0.09 to 0.02 between pretest average daily gain (ADG) and ADG at various test intervals. The low environmental correlations suggest that the performance of calves centrally tested at the Brandon and Lacombe Research Stations were not affected by the pre-test herd environment. Key words: Beef cattle, station test, pretest herd effects, environmental correlation

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