Traditional Methods Of Genetic Improvement

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1. Literature review 1 . 1. Traditional methods of genetic improvement Farmers have been making mate selection decisions for the improvement of livestock for generations. Whilst progress was evident, it was slow until the mid-20th century, when substantial gains in genetic improvement in both livestock and crops was observed. A good example of this progress is the increase in milk yield of US Holstein cattle which doubled from 6000kg per lactation in the 1960s to 1200kg per lactation in 2000. Up to 50% of this improvement has been accredited to genetic improvement (Dekkers and Hospital, 2002). These gains were brought about using quantitative techniques to estimate the genetic and environmental components of traits, as well as an improved ability to disseminate genetic material, such as cryopreservation of semen/embryos and artificial insemination. Whilst the genetic architecture of a trait is presumed to be complex, it is not known (Hill, 2010). Best Linear Unbiased Prediction (BLUP)methodology utilises a linear mixed model to combine phenotypic and pedigree information to calculate an individual’s estimated breeding value (EBVs), which is used as a measure of an organism’s additive genetic worth (Henderson, 1975). This technique was quickly adopted as the standard method to calculate EBVs. Despite this success, BLUP does have disadvantages. Without phenotypic information about an individual or it’s close relatives it is not capable of calculating EBVs. Genomic
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