Abstract
Human concern about the status of genetic diversity in livestock breeds and their conservation has increased, as intense selection and reduced population sizes in many breeds has caused losses on the global livestock genetic biodiversity. Traditionally, pedigree data provided by the breeders were used to estimate genetic diversity parameters, but over the past decades, technology has made possible the development of genomic markers. The result has been new opportunities to estimate genetic diversity in more detail, and to improve selection as well as prioritizing animals for conservation of genetic resources. The aim of the review is to summarize the evolution of livestock genomic markers and to explore the potential of the newest high-throughput technologies for estimation and conservation of livestock genetic diversity. More accurate diversity parameters are observed when genomic information is used for selection decisions instead of the traditional estimates using pedigree data. It is also possible to estimate additional parameters such as linkage disequilibrium to calculate effective population size or to minimize the genetic relatedness among the selected individuals based on runs of homozygosity. For long-term perspectives, new methods on genome editing are considered as new perspectives to reach a genetic diversity balance.
Highlights
Numerous countries have joined efforts to create the Commission on Genetic Resources for Food and Agriculture in response to the concerns about the threats and challenges that livestock species are presently facing, such as climate change, new diseases, restrictions on the availability of natural resources and changing market demands. These efforts were taken in order to promote the sustainable management of livestock diversity and to increase the diverse range of Animal Genetic Resources (AnGR) available to adapt to those challenges
(1) In many local breeds, because of extensive management systems, the absence of pedigrees is common; (2) it is assumed that founders are unrelated and carry two different alleles in all loci; (3) a common assumption when measuring genetic relationships based on pedigree information is that full siblings share exactly 50% of their genes, but this can vary considerably; (4) in subdivided populations without genealogical connections, it is impossible to estimate the genetic relationships among sub-populations, such as the caste study on the Lidia breed, which we will explain later
This information can be used in conservation programs in order to maintain genetic diversity and to assure performance in functional or fitness related traits, which may improve the probability of survival of the population itself
Summary
Domestic farm animals contribute daily to the livelihoods of millions of people. Around two billion people (one third of the global population) depend on farm animals for their livelihoods. (1) In many local breeds, because of extensive management systems, the absence of pedigrees is common; (2) it is assumed that founders are unrelated and carry two different alleles in all loci; (3) a common assumption when measuring genetic relationships based on pedigree information is that full siblings share exactly 50% of their genes, but this can vary considerably; (4) in subdivided populations without genealogical connections, it is impossible to estimate the genetic relationships among sub-populations, such as the caste study on the Lidia breed, which we will explain later In spite of these drawbacks, pedigree records are still important tools in conservation genetics analysis, in a way that they can inform on gene-mapping analyses, provide data for demographic studies and assess population structure in advance of genotyping in those populations, to mention some [5,6,7].
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