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Author G P Aamand

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Practical implementation of genetic groups in single-step genomic evaluations with Woodbury matrix identity-based genomic relationship inverse.

M Koivula, I Strandén, G P Aamand, E A Mäntysaari,

The growing amount of genomic information in dairy cattle has increased computational and modeling challenges in the single-step evaluations. The computational challenges are due to the dense inverses of genomic (G) and pedigree (A<sub>22</sub>) relationship matrices of genotyped animals in the single-step mixed model equations. An equivalent mixed model equation ... Read more >>

J Dairy Sci (Journal of dairy science)
[2021, :]

Cited: 0 times

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Metafounder approach for single-step genomic evaluations of Red Dairy cattle.

A A Kudinov, E A Mäntysaari, G P Aamand, P Uimari, I Strandén,

Single-step genomic BLUP (ssGBLUP) is a powerful approach for breeding value prediction in populations with a limited number of genotyped animals. However, conflicting genomic (G) and pedigree (A22) relationship matrices complicate the implementation of ssGBLUP into practice. The metafounder (MF) approach is a recently proposed solution for this problem and ... Read more >>

J Dairy Sci (Journal of dairy science)
[2020, 103(7):6299-6310]

Cited: 1 time

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Short communication: Multivariate outlier detection for routine Nordic dairy cattle genetic evaluation in the Nordic Holstein and Red population.

H Gao, P Madsen, J Pösö, G P Aamand, M Lidauer, J Jensen,

It is of practical importance to ensure the data quality from a milk-recording system before use for genetic evaluation. A procedure was developed for detection of multivariate outliers based on an approximation for Mahalanobis distance and was implemented in the Nordic Holstein and Red population. The general target of this ... Read more >>

J Dairy Sci (Journal of dairy science)
[2018, 101(12):11159-11164]

Cited: 2 times

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Short communication: Genomic prediction using different single-step methods in the Finnish red dairy cattle population.

H Gao, M Koivula, J Jensen, I Strandén, P Madsen, T Pitkänen, G P Aamand, E A Mäntysaari,

Single-step genomic prediction models utilizing both genotyped and nongenotyped animals are likely to become the prevailing tool in genetic evaluations of livestock. Various single-step prediction models have been proposed, based either on estimation of individual marker effects or on direct prediction via a genomic relationship matrix. In this study, a ... Read more >>

J Dairy Sci (Journal of dairy science)
[2018, 101(11):10082-10088]

Cited: 6 times

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Detection of evaluation bias caused by genomic preselection.

A-M Tyrisevä, E A Mäntysaari, J Jakobsen, G P Aamand, J Dürr, W F Fikse, M H Lidauer,

The aim of this simulation study was to investigate whether it is possible to detect the effect of genomic preselection on Mendelian sampling (MS) means or variances obtained by the MS validation test. Genomic preselection of bull calves is 1 additional potential source of bias in international evaluations unless adequately ... Read more >>

J Dairy Sci (Journal of dairy science)
[2018, 101(4):3155-3163]

Cited: 3 times

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Reducing bias in the dairy cattle single-step genomic evaluation by ignoring bulls without progeny.

M Koivula, I Strandén, G P Aamand, E A Mäntysaari,

The number of genotyped animals has increased rapidly creating computational challenges for genomic evaluation. In animal model BLUP, candidate animals without progeny and phenotype do not contribute information to the evaluation and can be discarded. In theory, genotyped candidate animal without progeny can bring information into single-step BLUP (ssGBLUP) and ... Read more >>

J Anim Breed Genet (Journal of animal breeding and genetics = Zeitschrift fur Tierzuchtung und Zuchtungsbiologie)
[2018, 135(2):107-115]

Cited: 4 times

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Validation of consistency of Mendelian sampling variance.

A-M Tyrisevä, W F Fikse, E A Mäntysaari, J Jakobsen, G P Aamand, J Dürr, M H Lidauer,

Experiences from international sire evaluation indicate that the multiple-trait across-country evaluation method is sensitive to changes in genetic variance over time. Top bulls from birth year classes with inflated genetic variance will benefit, hampering reliable ranking of bulls. However, none of the methods available today enable countries to validate their ... Read more >>

J Dairy Sci (Journal of dairy science)
[2018, 101(3):2187-2198]

Cited: 1 time

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Solving efficiently large single-step genomic best linear unbiased prediction models.

I Strandén, K Matilainen, G P Aamand, E A Mäntysaari,

Single-step genomic BLUP (ssGBLUP) requires a dense matrix of the size equal to the number of genotyped animals in the coefficient matrix of mixed model equations (MME). When the number of genotyped animals is high, solving time of MME will be dominated by this matrix. The matrix is the difference ... Read more >>

J Anim Breed Genet (Journal of animal breeding and genetics = Zeitschrift fur Tierzuchtung und Zuchtungsbiologie)
[2017, 134(3):264-274]

Cited: 16 times

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Effect of cow reference group on validation reliability of genomic evaluation.

M Koivula, I Strandén, G P Aamand, E A Mäntysaari,

We studied the effect of including genomic data for cows in the reference population of single-step evaluations. Deregressed individual cow genetic evaluations (DRP) from milk production evaluations of Nordic Red Dairy cattle were used to estimate the single-step breeding values. Validation reliability and bias of the evaluations were calculated with ... Read more >>

Animal (Animal : an international journal of animal bioscience)
[2016, 10(6):1061-1066]

Cited: 6 times

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Including different groups of genotyped females for genomic prediction in a Nordic Jersey population.

H Gao, P Madsen, U S Nielsen, G P Aamand, G Su, K Byskov, J Jensen,

Including genotyped females in a reference population (RP) is an obvious way to increase the RP in genomic selection, especially for dairy breeds of limited population size. However, the incorporation of these females must be conducted cautiously because of the potential preferential treatment of the genotyped cows and lower reliabilities ... Read more >>

J Dairy Sci (Journal of dairy science)
[2015, 98(12):9051-9059]

Cited: 6 times

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Single-step genomic model improved reliability and reduced the bias of genomic predictions in Danish Jersey.

P Ma, M S Lund, U S Nielsen, G P Aamand, G Su,

A bias in the trend of genomic estimated breeding values (GEBV) was observed in the Danish Jersey population where the trend of GEBV was smaller than the deregressed proofs for individuals in the validation population. This study attempted to improve the prediction reliability and reduce the bias of predicted genetic ... Read more >>

J Dairy Sci (Journal of dairy science)
[2015, 98(12):9026-9034]

Cited: 8 times

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Economic basis for the Nordic Total Merit Index.

M Kargo, L Hjortø, M Toivonen, J A Eriksson, G P Aamand, J Pedersen,

Within a group of cooperating countries, all breeding animals are judged according to the same criteria if a joint breeding goal is applied in these countries. This makes it easier for dairy farmers to compare national and foreign elite bulls and may lead to more selection across borders. However, a ... Read more >>

J Dairy Sci (Journal of dairy science)
[2014, 97(12):7879-7888]

Cited: 7 times

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Sharing reference data and including cows in the reference population improve genomic predictions in Danish Jersey.

G Su, P Ma, U S Nielsen, G P Aamand, G Wiggans, B Guldbrandtsen, M S Lund,

Small reference populations limit the accuracy of genomic prediction in numerically small breeds, such like Danish Jersey. The objective of this study was to investigate two approaches to improve genomic prediction by increasing size of reference population in Danish Jersey. The first approach was to include North American Jersey bulls ... Read more >>

Animal (Animal : an international journal of animal bioscience)
[2016, 10(6):1067-1075]

Cited: 9 times

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Short communication: Improving accuracy of Jersey genomic evaluations in the United States and Denmark by sharing reference population bulls.

G R Wiggans, G Su, T A Cooper, U S Nielsen, G P Aamand, B Guldbrandtsen, M S Lund, P M VanRaden,

The effect on prediction accuracy for Jersey genomic evaluations of Danish and US bulls from using a larger reference population was assessed. Each country contributed genotypes from 1,157 Jersey bulls to the reference population of the other. Data were separated into reference (US only, Danish only, and combined US-Danish) and ... Read more >>

J Dairy Sci (Journal of dairy science)
[2015, 98(5):3508-3513]

Cited: 8 times

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Single-step genomic evaluation using multitrait random regression model and test-day data.

M Koivula, I Strandén, J Pösö, G P Aamand, E A Mäntysaari,

The objectives of this study were to evaluate the feasibility of use of the test-day (TD) single-step genomic BLUP (ssGBLUP) using phenotypic records of Nordic Red Dairy cows. The critical point in ssGBLUP is how genomically derived relationships (G) are integrated with population-based pedigree relationships (A) into a combined relationship ... Read more >>

J Dairy Sci (Journal of dairy science)
[2015, 98(4):2775-2784]

Cited: 22 times

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Comparison of genomic predictions using medium-density (∼54,000) and high-density (∼777,000) single nucleotide polymorphism marker panels in Nordic Holstein and Red Dairy Cattle populations.

G Su, R F Brøndum, P Ma, B Guldbrandtsen, G P Aamand, M S Lund,

This study investigated genomic prediction using medium-density (∼54,000; 54K) and high-density marker panels (∼777,000; 777K), based on data from Nordic Holstein and Red Dairy Cattle (RDC). The Holstein data comprised 4,539 progeny-tested bulls, and the RDC data 4,403 progeny-tested bulls. The data were divided into reference data and test data ... Read more >>

J Dairy Sci (Journal of dairy science)
[2012, 95(8):4657-4665]

Cited: 65 times

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Genomic prediction for Nordic Red Cattle using one-step and selection index blending.

G Su, P Madsen, U S Nielsen, E A Mäntysaari, G P Aamand, O F Christensen, M S Lund,

This study investigated the accuracy of direct genomic breeding values (DGV) using a genomic BLUP model, genomic enhanced breeding values (GEBV) using a one-step blending approach, and GEBV using a selection index blending approach for 15 traits of Nordic Red Cattle. The data comprised 6,631 bulls of which 4,408 bulls ... Read more >>

J Dairy Sci (Journal of dairy science)
[2012, 95(2):909-917]

Cited: 70 times

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Effects of complex vertebral malformation on fertility traits in Holstein cattle

U S Nielsen, G P Aamand, O Andersen, C Bendixen, V H Nielsen, J S Agerholm,

Previous studies have indicated that the viability of bovine foetuses affected by complex vertebral malformation (CVM) is reduced. To study this a data analysis was performed. Breeding data on Holstein cows being daughters of confirmed CVM carriers and inseminated first time after calving with semen of a sire with established ... Read more >>

Livest Prod Sci (Livestock production science)
[2003, 79(2-3):233-238]

Cited: 15 times

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Evaluation of the inheritance of the complex vertebral malformation syndrome by breeding studies.

J S Agerholm, O Andersen, M B Almskou, C Bendixen, J Arnbjerg, G P Aamand, U S Nielsen, F Panitz, A H Petersen,

To investigate the congenital complex vertebral malformation syndrome (CVM) in Holstein calves, two breeding studies were performed including 262 and 363 cows, respectively. Cows were selected from the Danish Cattle Database based on pedigree and insemination records. Selected cows were progeny of sires with an established heterozygous CVM genotype and ... Read more >>

Acta Vet Scand (Acta veterinaria Scandinavica)
[2004, 45(3-4):133-137]

Cited: 11 times

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