Abstract
Quantitative trait loci (QTL) affecting fatness in male chickens were previously identified on chromosome 5 (GGA5) in a three-generation design derived from two experimental chicken lines divergently selected for abdominal fat weight. A new design, established from the same pure lines, produced 407 F2 progenies (males and females) from 4 F1-sire families. Body weight and abdominal fat were measured on the F2 at 9 wk of age. In each sire family, selective genotyping was carried out for 48 extreme individuals for abdominal fat using seven microsatellite markers from GGA5. QTL analyses confirmed the presence of QTL for fatness on GGA5 and identified a QTL by sex interaction. By crossing one F1 sire heterozygous at the QTL with lean line dams, three recombinant backcross 1 (BC1) males were produced and their QTL genotypes were assessed in backcross 2 (BC2) progenies. These results confirmed the QTL by sex interaction identified in the F2 generation and they allow mapping of the female QTL to less than 8 Mb at the distal part of the GGA5. They also indicate that fat QTL alleles were segregating in both fat and lean lines.
Highlights
In meat-type chickens, deposition of excessive adipose tissue decreases both feed efficiency and yield of lean meat
Quantitative trait loci (QTL) for abdominal fat weight at 9-weeks of age adjusted for sex and body weight (AF) was investigated on GGA5 in F2 and back-cross generations
This study confirmed the existence of fatness QTL on GGA5 as already reported in the FL and LL [29] and in other genetic backgrounds [24,31]
Summary
In meat-type chickens, deposition of excessive adipose tissue decreases both feed efficiency and yield of lean meat. The identification of genes responsible for fat deposition could improve meat-chicken production through the breeding process and it would meet the consumer demand for leaner meat. Various experimental designs have been used for the identification of at least 26 fatness QTL [24, 26, 29, 42]. The recombinant progeny testing method is one of the most commonly used to refine QTL regions [6]. Fatness was measured in both males and females which allowed detection of the QTL by sex interaction This interaction was found in further back-cross generations in which recombinant events allowed the female QTL to be mapped to
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