Additive and Nonadditive Genetic Effects on Growth and Milk Production Traits in Holstein Ayrshire Crossbreeding Experimental Data PDF Download
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Author: Daniel Perotto Publisher: ISBN: Category : Ayrshire cattle Languages : en Pages : 430
Book Description
"Estimates of crossbreeding parameters from mixed-model analyses, were found to be more reliable than those from ordinary least squares analyses. (Abstract shortened by UMI.)" --
Author: Daniel Perotto Publisher: ISBN: Category : Ayrshire cattle Languages : en Pages : 430
Book Description
"Estimates of crossbreeding parameters from mixed-model analyses, were found to be more reliable than those from ordinary least squares analyses. (Abstract shortened by UMI.)" --
Author: Kristen Alves Publisher: ISBN: Category : Languages : en Pages :
Book Description
In animal breeding, it is assumed that majority of the variation in a phenotype can be captured by gene variants which combine their effects in an additive manner. In dairy cattle, this assumption works well for most traits. However, for low heritability and complex traits such as fertility and reproduction traits, additive genetic effects may not capture most of the variation. This thesis set out to explore whether it is possible to capture interactions between alleles at one loci (dominance) and between alleles at different loci (additive by additive epistasis) to improve our understanding of the genetic architecture and control of fertility and reproduction traits in Holstein cattle. Additive, dominance, and epistatic genetic variance components using pedigree and genomic relationship matrices were estimated. Dominance and epistasis contributed a larger proportion of the total phenotypic variance than the additive model currently used in practice. Three transformations to the Hadamard product for deriving the epistatic relationship matrix on the estimation of epistatic genetic variance components was investigated. While removing the interaction of a marker with itself decreased the confounding between additive and epistatic genetic effects, there was not a clear advantage as to which matrix was best. Genomic predictions were performed to assess the impact of including genomic information, epistasis, and the variants of the epistatic genomic relationship matrix on the reliability of and bias in model predictions. The results suggest fitting epistatic genetic effects in genomic evaluation models may yield an improvement in the prediction of breeding values and future phenotypes. Lastly, a genome-wide association study was performed to investigate the genetic architecture of the traits. The results suggest that significant epistatic genetic effects are probably due to many loci with a small effect rather than few loci with a large effect. Improving our understanding of the genetic architecture and control of fertility and reproduction traits will help in the proper estimation of breeding values and correct ranking of candidate parents for the next generation. This research emphasizes the need for a re-examination of our tools to help detect causal links between genetic and phenotypic variation.
Author: Milton Henry Fohrman Publisher: ISBN: Category : Agriculture Languages : en Pages : 132
Book Description
In 1939, when the Bureau of Dairy Industry began its crossbreeding experiment at Beltsville, the published information on the crossbreeding of dairy cattle was slight, unimpressive, and very little of it was based on experimental results. The crossbreeding investigations at Beltsville were undertaken to develop knowledge on the subject which would provide a sound basis for advising the operators of milk-producing farms what to expect if they used crossbreeding in hopes of producing better replacements for their milking herds. Final results on any dairy cattle breeding research project cannot be published until the last animal on the project has died, so this report covers the breeding performance and milk and butterfat production on all individuals used on the project which have had time to complete a normal first-lactation period.
Author: Daniel Perotto
Author: Daniel Perotto
Author: Kristen Alves
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Author: B. Kebede
Author: Eva Maria Strucken
Author: Milton Henry Fohrman
Author: A. Neimann-Sørensen
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Author: 
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