A partial genome scan to map quantitative trait loci for carcass composition, as assessed by X-ray computer tomography, and meat quality traits in Scottish Blackface Sheep

Abstract

Quantitative trait loci (QTL) were identified for traits related to carcass and meat quality in Scottish Blackface sheep. The population studied was a double backcross between lines of sheep divergently selected for carcass lean content (LEAN and FAT lines), comprising nine half-sib families. Carcass composition (600 lambs) was assessed non-destructively using computerized tomography (CT) scanning and meat quality measurements (initial and final pH of m. semimembranosus, colour, shear force value, carcass weight, lamb flavour, juiciness, tenderness and overall liking) were taken on 300 male lambs. Lambs and their sires were genotyped across candidate regions on chromosomes 1, 2, 3, 5, 14, 18, 20 and 21. QTL analyses were performed using regression interval mapping techniques. In total, nine genome-wise significant and 11 chromosome-wise and suggestive QTL were detected in seven out of eight chromosomes. Genome-wise significant QTL were mapped for lamb flavour (OAR 1); for muscle densities (OAR 2 and OAR 3); for colour a*(redness) (OAR 3); for bone density (OAR 1); for slaughter live weight (OAR 1 and OAR 2) and for the weights of cold and hot carcass (OAR 5). The QTL with the strongest statistical evidence affected the lamb flavour of meat and was on OAR 1, in a region homologous with a porcine SSC 13 QTL identified for pork flavour. This QTL segregated in four of the nine families. This study provides new information on QTL affecting meat quality and carcass composition traits in sheep, which may lead to novel opportunities for genetically improving these traits.

Genome-wide association and regional heritability mapping to identify loci underlying variation in nematode resistance and body weight in Scottish Blackface lambs

“…Nematode resistance loci in sheep V Riggio et al definitions (for example, Walling et al, 2004;McRae et al, 2005;Karamichou et al, 2006;Raadsma et al, 2009;Jonas et al, 2010). However, Hadjipavlou and Bishop (2008) have shown that body weight QTL changes over time in Scottish Blackface sheep.…”

Effects of a quantitative trait locus for increased muscularity on carcass traits measured by subjective conformation and fat class scores and video image analysis in crossbred lambs

“…CT scanning, which is currently being used in sheep breeding programs for the evaluation of carcass quality, could also provide the means to select on MQ traits. In two different studies (Karamichou et al, 2006;Navajas et al, 2006a), live CT measurements have been reported to predict MQ traits with moderate accuracy, most likely due to the associations between IMF and CT-measured muscle density. Karamichou et al (2006) reported significant phenotypic and genetic correlations between CT and meat eating quality traits, and Navajas et al (2006a) also found strong associations between CT muscle density and IMF.…”

Genetic analyses of sensory characteristics and relationships with fatty acid composition in the meat from Scottish Blackface lambs

“…A small proportion of reciprocal LEAN 3 FAT line crosses were made at the 1999 matings, so that a cohort of F 1 lambs were born in April 2000 along with a majority of purebred LEAN and FAT line lambs. The male F 1 lambs were then backcrossed to the purebred LEAN and FAT line ewes to create a population of F 1 3 LEAN and F 1 3 FAT lambs from 2001 to 2003, for the purpose of QTL detection (Karamichou et al, 2006b and2006c). A small number of F 1 3 (F 1 3 LEAN) and F 1 3 (F 1 3 FAT) were born in 2003 when female backcross lambs from 2001 themselves became dams.…”