Genetic variation of new sheep traits measured by dual energy Xray absorptiometry

Abstract

<p>Dual energy Xray absorptiometry (DEXA) is regularly used to measure body composition and bone characteristics in human medicine. Medical grade DEXA can accurately measure the proportion of fat, lean and bone in production animals, as well as bone minerals in lambs. Recently, DEXA modified for lamb carcase scanning at abattoir-chainspeed precisely predicted CT fat and lean % over a range of lamb genotypes. There is opportunity to measure new traits and identify the genetic variation of these traits on live sheep using a medical grade DEXA. Lambs from the Genetic Resource Flock (n=400) are live DEXA scanned at the Katanning Research Station and subsequently DEXA scanned as carcases at the processing facility. DEXA technology scans an object at two different energy levels. The ratio (R value) between the high and low energy level for each pixel in the image relates to the atomic mass of the tissue. Analysis will include whole body and sub-regional lean and fat %, and bone %. Individual pelvic bones are also analysed on the live DEXA scans to measure pelvic area and bone content. This data will provide the opportunity to identify correlations between live DEXA and carcase DEXA measures of body composition within and across sire types. Furthermore, there is potential to link individual bone analysis to important genetic reproduction traits such as lamb birthweight and lamb survival.</p>