Abstract
BackgroundTo satisfy an increasing demand for dietary protein, the poultry industry has employed genetic selection to increase the growth rate of broilers by over 400% in the past 50 years. Although modern broilers reach a marketable weight of ~ 2 kg in a short span of 35 days, a speed twice as fast as a broiler 50 years ago, the expedited growth has been associated with several negative detrimental consequences. Aside from heart and musculoskeletal problems, which are direct consequences of additional weight, the immune response is also thought to be altered in modern broilers.ResultsGiven that identifying the underlying genetic basis responsible for a less sensitive innate immune response would be economically beneficial for poultry breeding, we decided to compare the genomes of two unselected meat control strains that are representative of broilers from 1957 and 1978, and a current commercial broiler line. Through analysis of genetic variants, we developed a custom prioritization strategy to identify genes and pathways that have accumulated genetic changes and are biologically relevant to immune response and growth performance. Our results highlight two genes, TLR3 and PLIN3, with genetic variants that are predicted to enhance growth performance at the expense of immune function.ConclusionsPlacing these new genomes in the context of other chicken lines, reveal genetic changes that have specifically arisen in selective breeding programs that were implemented in the last 50 years.
Highlights
To satisfy an increasing demand for dietary protein, the poultry industry has employed genetic selection to increase the growth rate of broilers by over 400% in the past 50 years
Genome sequencing reveals the modern broiler to be closely related to the 1957 and 1978 lines The goal of this study was to identify the genetic basis for traits selected for in modern breeding programs, such as growth and feed efficiency, with the purpose of informing on the selection of otherwise unanticipated traits such as skeletal defects, metabolic disorders and altered immune function [2, 3, 17]
To this end we sequenced the genomes of two University of Alberta Meat Control lines, unselected since 1957 and 1978 and representing synthetic crosses of a large number of contemporary commercial broiler lines, and a 2016 commercial Ross 308 broiler
Summary
To satisfy an increasing demand for dietary protein, the poultry industry has employed genetic selection to increase the growth rate of broilers by over 400% in the past 50 years. A study of 12 diversified chicken genomes identified a number of copy number variable regions covering genes that include FZD6 and LIMS1, which have been associated with increased resistance to Marek’s disease [11], while a comparison of Leghorn and Fayoumi chickens identified a duplication of BD7, involved in host innate immune response, in the latter [15]. These studies have focused on pairwise comparisons of individual lines, as opposed to genetic variation that occurs within the context of a breeding program. The availability of lines with shared ancestry that have undergone selective breeding over a number of decades, offers an opportunity to explore how the accumulation of genetic traits might impact phenotype
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