Effects of a quantitative trait locus for muscle hypertrophy from Belgian Texel sheep on carcass conformation and muscularity

Abstract

A QTL for muscle hypertrophy has been identified in the Belgian Texel breed. A population of F2 and backcross lambs created from crosses of Belgian Texel rams with Romanov ewes was studied. Effects on carcass traits and muscle development of the Belgian Texel breed polygenes and Belgian Texel single QTL were compared. In both cases, carcass conformation and muscularity were improved. The Texel polygenic environment improved conformation mainly through changes in skeletal frame shape. Segments were shorter and bone weight lower. Muscles were more compact, shorter, and thicker. The single QTL affected muscle development. Thickness and weight of muscles were increased. Composition in myosin changed toward an increase of fast contractile type. The relative contribution of hind limb joint to carcass weight was increased. Differences in skeletal frame morphology among the three genotypes of the single QTL were small. Conformation scoring was mainly influenced by leg muscularity. Back and shoulder muscle development, which largely contributed to variability of muscularity, were less involved in the conformation scoring. Lastly, the QTL explains a small part of differences between these Belgian Texel and Romanov breeds for conformation or muscle development. A large part of genetic variability remains to be explored.

QTL mapping for sexually dimorphic fitness-related traits in wild bighorn sheep

“…Three additional regions (out of 5) with LOD scores smaller than genome-wide significance thresholds appeared to be colocalized with domestic sheep weight-related QTLs. In domestic sheep, these regions contain QTLs for body weight and muscularity (chromosome 2, Laville et al, 2004;Walling et al, 2004;Margawati et al, 2009), body weight and growth rate (chromosome 23, Margawati et al, 2006Margawati et al, , 2009Raadsma et al, 2009) and body weight, growth rate and muscle mass (chromosome 24, Campbell et al, 2003;Raadsma et al, 2009). Possible candidate genes in these regions (genes known to influence weight-related traits in sheep or other species) identified by Raadsma et al (2009) include myostatin, beta-3-adrenergic receptor, melanocortin 4 receptor, erythropoietin, elastin and fibrosin genes.…”

Sire carcass breeding values affect body composition in lambs — 1. Effects on lean weight and its distribution within the carcass as measured by computed tomography

“…Consumer preferences in domestic and international markets drive the industry to produce meat cuts that are larger and leaner (Banks, 2002;Hall, Kelf, Fogarty, & Murray, 2000;Laville, Bouix, Sayd, & Bibé, 2004). To achieve this goal, Australian lamb producers currently select for lean meat yield percentage indirectly via three existing Australian Sheep Breeding Values (ASBVs) for postweaning weight (PWWT), c-site fat depth (PFAT) and eye muscle depth (PEMD), which are used to select for improved growth, leanness and muscling respectively.…”

The effects of a loin muscling quantitative trait locus (LoinMAX™) on carcass and VIA-based traits in crossbred lambs

“…Macfarlane et al (2009) studied the TM-QTL effects on hind leg muscle volume and hind leg muscle density and analyses revealed no significant difference between carrier and non-carrier lambs. This study did not find any significant effects of the LM-QTL on the hind leg muscle characteristics of width, depth and 2D muscularity measured by CT. Muscularity describes the shape of the muscle and it has been shown that deeper muscles appeal to consumers, as they prefer rounded rather than thin chops (Laville et al, 2004). LM-QTL carrier lambs showed no significant change in muscularity in both the leg and loin regions, as measured from 2D CT scans.…”

“…This can be achieved by -E-mail: amer.masri@sac.ac.uk incorporating this information into breeding programmes through marker-assisted selection (MAS) schemes (Dekkers and Hospital, 2002;Dekkers, 2004). To date, many genes and QTLs affecting the muscle growth, carcass composition and meat quality have been reported in farm animals, several of which are found in sheep (Cockett et al, 1994;Nicoll et al, 1998;Broad et al, 2000;Marcq et al, 2002;Laville et al, 2004;Walling et al, 2004;Clop et al, 2006;Kijas et al, 2007;Hadjipavlou et al, 2008). However, very few causative mutations underlying the variations associated with traits of economic importance in sheep have been successfully identified and validated (Cockett et al, 1994;Clop et al, 2006;Wilson et al, 2001).…”