Use of X-Ray Computed Tomography (CT) in UK Sheep Production and Breeding

Abstract

The aim of this chapter was to review the use of computed tomography (CT) in UK sheep breeding to improve carcass composition and elements of meat quality, as well as the use of CT scanning as a benchmarking system for faster and cheaper carcass evaluation for use both in practise for the livestock industry and for furthering research aims. This paper will review some of the work carried out at the Scottish Agricultural College (SAC) in collaboration with Biomathematics & Statistics Scotland (BioSS) in the last 14 years. The work investigated the use of CT scanning alongside ultrasound scanning (US) in a synergistic approach to benefit the UK sheep industry by improving the breeding value of terminal sire (meat) rams. In vivo measurements via CT of body composition of the top ranking male selection candidates (pre-selected by their US measured backfat and muscle depth) are used to enhance the accuracy of selection decisions regarding carcass quality and more recently, also some components of meat quality. CT-derived information provides both directly measured traits for use in the breeding process as well as serving as a bench-marking system for the validation of other techniques such as Video image analysis (VIA) or ultrasound scanning. It also has real potential to replace the “Gold Standard” of carcass evaluation which has always been used in past, which is the dissection of carcass tissues into component parts. Initially, we will characterise UK sheep breeding and the need to accurately and precisely measure body and carcass composition of breeding animals or their close relatives with the aim of improving the quality of slaughter lambs. UK sheep industry. There are around 15 million breeding ewes in the UK (www.defra.gov.uk/evidence/statistics/foodfarm/general/auk/latest/excel/index.htm), half of which are purebred and half are crossbred, with hill and lowland areas each containing around 40% of the ewes and upland areas the remaining 20% (Pollott & Stone, 2006). The UK sheep industry is characterised by a stratified structure, which has evolved over many years to best utilise the available land and to match breeds or crosses to different systems. The stratified system has different selection goals within each strata and makes use of specialised sire and dam breeds and crosses and exploits both the complementarities of breeds for crossing e.g. longwool (litter size, milk) x hill (hardiness, intermediate mature