The effect of TM-QTL and other QTLs on lean meat yield and meat quality in sheep and its evaluation using VISA

Please refer to Principal Investigator's Proposal

This project brings together 2 interlinked developments needing further investigation: i) evaluation of QTLs increasing LMY, and ii) the potential of VISA to estimate LMY. Recent research in the UK and NZ has identified 3 QTLs increasing LMY. However, comprehensive validation of both their direct and indirect effects is needed. VISA based carcass classification is about to be introduced into the UK. It may underpin a value-based marketing system with the potential to reward farmers for the use of 'new genetics', but requires detailed validation and refinement to predict LMY. This project has therefore 2 main aims: 1) provide a comprehensive validation of three QTLs for increasing LMY, and 2) test and calibrate the VISA-system, which will be delivered through following sub-objectives (O): O1.1 evaluate the direct and indirect effects of the TM-QTL, in purebred Texels using 210 lambs; O1.2 evaluate the direct and indirect effects (as in O1.1) above) in crossbred lambs produced out of Mule ewes, using 70 wildtype and 70 heterozygous lambs; Os 1.3 and 1.4 evaluate the direct and some indirect effects of LM-QTL and MM-QTL, as per O1.2. O1.5 to evaluate the direct effects of the TM-QTL and MM-QTL in crossbred lambs out of Welsh Mountain ewes; O1.6 introgress both the TM-QTL and MM-QTL into purebred Inverdale-Texel sheep, and to introgress the TM-QTL into other Terminal Sire breeds using marker assisted backcrossing, to produce some carrier rams for more widespread introduction of the QTL within these breeds; O2.1 investigate the associations of VISA-traits with carcass composition measured by CT and dissection; O2.2 predict the relationships between VISA-traits and meat quality based on 210 purebred Texel and 140 crossbred lambs, representing the different TM-QTL genotypes; O2.3 use the TM-QTL, LM-QTL and MM-QTL to estimate their effect on VISA characteristics; O2.4 estimate genetic parameters for VISA-traits as a pre- requisiste for their integration into breeding programmes.