Variance components — some history and a summary account of estimation methods

Searle, S. R.

doi:10.1111/j.1439-0388.1989.tb00209.x

Cited by 30 publications

(20 citation statements)

References 55 publications

(60 reference statements)

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“…1987, Meyer 1989, Searle 1989, Misztal 1990, Foulley 1993. Bu tercihin en önemli nedenleri; yöntemin negatif de ğerli varyans tahmini vermemesi ve alt gruplardaki gözlem say ı ları n ı n farkl ı olmas ı ndan ileri gelecek sapmalar ı en aza indirmeyi hedeflemesidir.…”

Section: Hayvanunclassified

Türkiye Siyah Alaca Populasyonunda 305-Gün Süt Verimine Ait Genetik ve Fenotipik Parametreler

Numan;KUMLU¹

2004

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Özet: Türkiye Dam ı zl ı k S ığı r Yeti ştiricileri Merkez Birli ği tarafı ndan süt verimi esas al ı narak yürütülen ı slah program ı n ı n gere ğ i olan genetik ve fenotipik parametrelerin tahmin edilmesi amac ı yla yap ı lan bu çal ış ma, Merkez Birli ğ i veri taban ı nda bulunan Siyah Alaca ı rk ı s ığı rları n soy bilgileri ve 305-gün laktasyon süt verim kay ı tlar ı kullan ı larak gerçekleştirilmi ştir. Ara ştı rmada 9655 ba ş ineğ in 1990-2001 y ı lları n aras ı nda başlam ış ilk 3 laktasyonuna ait toplam 15910 laktasyon kayd ı kullan ı lm ıştı r. Akrabal ı k matrisini olu şturmada kullan ı lan soy dosyas ı nda 22145 baş hayvan ve 222 genetik grup yer alm ışt ı r. Eklemeli genetik varyans, sabit çevre varyans ı , fenotipik varyans, kal ı tı m derecesi, sabit çevre varyans ı n ı n pay ı , tekrarlanma derecesi ve fenotipik varyasyon katsay ı sı s ı ras ıyla; 349636, 320903, 1574935, 0.222 ± .0288, 0.204 ± 0.0256, 0.426 ± 0.0102 ve % 21.8 olarak tahmin edilmi ştir. Gerçek ve tahmin edilen dam ı zl ı k değ erleri aras ı ndaki korelasyon katsay ı s ı olarak tan ı mlanan isabet derecesi için ortalama de ğ er % 54.8 olarak hesaplanm ıştı r.Anahtar Kelimeler: Siyah Alaca, süt verimi, kal ıt ı m derecesi, tekrarlanma derecesi Genetic and Phenotypic Parameters for 305-Day Milk Yield of Turkish Holstein PopulationAbstract: This study has been carried out to estimate the genetic and phenotypic parameters for 305-day milk yields of Turkish Holstein cattle to use in breeding program of Turkish Holstein Breeder's Association. The data set used in this study consisted of 15 910 first, second and third lactation milk records of 9655 cows calved between 1990 and 2001 years. The pedigree file used to build relationship matrix was cowered 22145 animals and 222 genetic groups. Estimates of additive-genetic variance, permanent variance, phenotypic variance, heritability, permanent variance ratio, repeatability and phenotypic coefficient of variation were 349636, 320903, 1574935, 0.222 ± 0.0288, 0.204 ± 0.0256, 0.426 ± 0.0102 and 21.8% respectively. The general accuracy of predictions defined as correlation between true and predicted breeding values was calculated as 54.8%.

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Section: Hayvanunclassified

Türkiye Siyah Alaca Populasyonunda 305-Gün Süt Verimine Ait Genetik ve Fenotipik Parametreler

Numan;KUMLU¹

2004

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“…REML approaches do not supply unbiased estimates ( S EARLE 1989). Therefore, all hypothesis tests (e.g.…”

Section: Hypothesis Testingmentioning

confidence: 99%

“…where, R^ = R^ / n , R^ is an estimated ratio of two selected variance components, n is the number of generated samples, R is the value of R^ chosen in the computer simulation and s R^ = √ s 2 R^ / n with s 2 R^ =the actual variance of R^ in the n generated samples. Expression (15) is based on the assumption that REML estimates have asymptotic normality properties ( S EARLE 1989). Thus, t a should approximately follow a t ‐distribution with infinite degrees of freedom.…”

Section: Hypothesis Testingmentioning

confidence: 99%

Estimation of variance components due to imprinting effects with DFREML and VCE: results of a simulation study

Essl¹,

Voith²

2002

J Animal Breeding Genetics

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Treating gametes as homozygous diploid individuals, TIER and SÖLKNER (Theor. Appl. Genet. 85: 868–872, 1993) proposed a method which manages the use of available computer programs with a common animal model to estimate variance components caused by imprinting effects. Despite some relevant model restrictions, this approach has already been used in some field data analyses by an adapted version of the widely used DFREML computer program, subsequently indicated by DFREMLa. The main objective of this study was to ascertain the properties of DFREMLa by computer simulation and to examine other alternative estimation approaches. The most important results may be summarized as follows: (1) Treating gametes as homozygous diploid individuals has the consequence that one‐half of the actually realized gametic effect is totally abstracted in variance component estimation. Thus, an additional adjustment of the phenotypic variance calculated by DFREMLa is necessary to get correct values of estimated variance component ratios. (2) Adjusted DFREMLa estimates yielded correct results when animals were unselected and only maternal or paternal imprinting (not both simultaneously) occurred. (3) When the model did not adequately account for the additive genetic component within a maternal lineage, significant upward biases for the cytoplasmic component were observed. (4) The use of a simple dam and sire model with appropriate relationship matrices can be recommended when only the difference of maternal and paternal imprinting effects is of primary interest and the covariance between maternal halfsibs is not substantially increased by common environmental effects. (5) An adequate estimation of variance components for all possible imprinting situations requires the use of an animal model augmented by both maternal and paternal gametic effects. Unfortunately, a computer program on the basis of such a model does not yet exist.

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“…And as an estimation method it was given considerable impetus by the Anderson and Bancroft (1952) book wherein it is considered at some length. More details of this history are to be found in Searle (1989).…”

Section: Thehendersonlandmarkmentioning

confidence: 99%

C. R. Henderson, the Statistician; And His Contributions to Variance Components Estimation

Searle¹

1991

Journal of Dairy Science

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By then, improved methods of estimating variance components from unbalanced data had been developed, namely maximum likelihood (ML) and restricted maximum likelihood (REML). Once computing power had expanded to the point where these methods became feasible "Chuck", in his later years, made notable contributions to these methods, allied to his two great interests: animal breeding, and feasible computing procedures.For both of these his mixed model equations were a salient feature.

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Variance components — some history and a summary account of estimation methods

Cited by 30 publications

References 55 publications

Türkiye Siyah Alaca Populasyonunda 305-Gün Süt Verimine Ait Genetik ve Fenotipik Parametreler

Türkiye Siyah Alaca Populasyonunda 305-Gün Süt Verimine Ait Genetik ve Fenotipik Parametreler

Estimation of variance components due to imprinting effects with DFREML and VCE: results of a simulation study

C. R. Henderson, the Statistician; And His Contributions to Variance Components Estimation

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