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

Abstract

and fat depth (mm; PFAT), and post weaning weight (kg; PWWT). Across the 7.8 unit range of sire PEMD, carcass lean weight increased by 7.7%. This lean was distributed to the saddle section (mid-section) where lean became 3.8% heavier, with fore section lean becoming 3.5% lighter. Reducing sire PFAT across its 5.1 unit range increased carcass lean weight by 9.5%, and distributed lean to the saddle section which was 3.7% heavier. Increasing sire PWWT increased lean at some sites in some years, and on average increased saddle lean by 4% across the 24.7 unit PWWT range. Changes in lean weight and distribution due to selection for carcass breeding values will increase carcass value, particularly through increased weight of high value loin cuts.

The impact of genetics on retail meat value in Australian lamb

“…This difference in lean weight was worth $3.58, and aligns well with the sire type effect discussed above where the lean from Merino lambs was worth $4.80 more than lambs from Maternal dams. Although not previously compared on a dollar basis, the mass differences align well with previous studies where, after correcting for carcass weight, lambs from BLM dams had less carcass lean (Anderson, Williams, et al, 2015a;Ponnampalam et al, 2008) and a higher proportion of fat (Anderson, Williams, et al, 2015b) than lambs from Merino dams.…”

“…Non-significant (P > 0.05) terms were removed in a stepwise manner. Although these ASBVs were correlated (PWWT vs PEMD = 0.3; PWWT vs PFAT = 0.3; PEMD vs PFAT = 0.1) previous analysis has demonstrated that their effects are still relatively independent when included simultaneously in a model predicting CT composition (Anderson, Williams, et al, 2015a, 2015b. …”

“…Lamb carcasses were divided into three sections (fore, saddle (middle) and hind): the fore section separated from the saddle by a cut between the fourth and fifth ribs; the hind section was separated from the saddle by a cut through the mid-length of the sixth lumbar vertebrae. A detailed description of the CT scanning process and calculation of carcass composition is presented in Anderson, Williams et al (2015a).…”

“…CT scanning data was available on 1554 of the lambs from an INF experiment described by Anderson, Williams et al (2015a) using 7 site-year combinations where lean measurement was available within the fore, saddle, and hind sections of the carcass (Table 1). In this experiment there were a total of 23 kill groups, with the raw average age of lamb 280 days and the number of lambs within each kill group ranging from 20 to 99 lambs (Table 1).…”

“…The full description of carcass weights of fat lean and bone across the three sections are reported in Anderson, Williams et al (2015a). Of the 81 Maternal, 119 Merino and 144 Terminal…”