Author
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Wiggans, George |
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GENGLER, NICOLAS - University Of Liege |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 6/20/2015 Publication Date: 12/1/2015 Citation: Wiggans, G.R., Gengler, N. 2015. Genetics: Selection: Evaluation and methods. In: Smithers, G.W., editor. Reference Module in Food Science. Amsterdam: Elsevier B.V. p. 1–7. doi: 10.1016/B978-0-08-100596-5.00801-5. Interpretive Summary: Technical Abstract: The procedures used for collecting and analyzing data for genetic improvement of dairy cattle are described. Methods of identification and milk recording are presented. Selection traits include production (milk, fat, and protein yields and component percentages), conformation (final score and linear type traits), fitness (mastitis, longevity, and fertility), and calving (dystocia and stillbirth). The genetic evaluation system has evolved from comparing cows with dams to comparing them with contemporaries to the animal model where contributions of all relatives are considered to genomic evaluations that also include information from animal genotypes. Evaluations are expressed relative to a genetic base, which sets the mean and in some cases the standard deviation of evaluations for animals in a base group (e.g., animals born in a particular year). Genetic bases are usually adjusted over time to reflect genetic improvement. The Interbull Centre in Sweden combines national evaluations from over 20 countries to provide an international ranking of all bulls on the scale of each participating country. Recent research has focused on using DNA information (single nucleotide polymorphisms) to estimate genetic merit early in an animal’s life before phenotypic records are available. This technology has substantially enhanced the rate of genetic improvement by increasing selection intensity and reducing generation interval with only a small loss in accuracy. |
