Genetic parameters for carcass and meat quality traits and their relationships to liveweight and wool production in hogget Merino rams

Abstract

Genetic parameters for carcass and meat quality traits of about 18-month-old Merino rams (n = 5870), the progeny of 543 sires from three research resource flocks, were estimated. The estimates of heritability for hot carcass weight (HCW) and the various fat and muscle dimension measurements were moderate and ranged from 0.20 to 0.37. The brightness of meat (colour L*, 0.18 +/- 0.03 standard error) and meat pH (0.22 +/- 0.03) also had moderate estimates of heritability, although meat relative redness (colour a*, 0.10 +/- 0.03) and relative yellowness (colour b*, 0.10 +/- 0.03) were lower. Heritability estimates for live weights were moderate and ranged from 0.29 to 0.41 with significant permanent maternal environmental effects (0.13 to 0.10). The heritability estimates for the hogget wool traits were moderate to high and ranged from 0.27 to 0.60. The ultrasound measurements of fat depth (FATUS) and eye muscle depth (EMDUS) on live animals were highly genetically correlated with the corresponding carcass measurements (0.69 +/- 0.09 FATC and 0.77 +/- 0.07 EMD). Carcass tissue depth (FATGR) had moderate to low genetic correlations with carcass muscle measurements [0.18 +/- 0.10 EMD and 0.05 +/- 0.10 eye muscle area (EMA)], while those with FATC were negative. The genetic correlation between EMD and eye muscle width (EMW) was 0.41 +/- 0.08, while EMA was highly correlated with EMD (0.89 +/- 0.0) and EMW (0.78 +/- 0.04). The genetic correlations for muscle colour with muscle measurements were moderately negative, while those with fat measurements were close to zero. Meat pH was positively correlated with muscle measurements (0.14 to 0.17) and negatively correlated with fat measurements (-0.06 to -0.18). EMDUS also showed a similar pattern of correlations to EMD with meat quality indicator traits, although FATUS had positive correlations with these traits which were generally smaller than their standard error. The genetic correlations among the meat colour traits were high and positive while those with meat pH were high and negative, which were all in the favourable direction. Generally, phenotypic correlations were similar or slightly lower than the corresponding genetic correlations. There were generally small to moderate negative genetic correlations between clean fleece weight (CFW) and carcass fat traits while those with muscle traits were close to zero. As the Merino is already a relatively lean breed, this implies that particular attention should be given to this relationship in Merino breeding programmes to prevent the reduction of fat reserves as a correlated response to selection for increased fleece weight. The ultrasound scan traits generally showed a similar pattern to the corresponding carcass fat and muscle traits. There was a small unfavourable genetic correlation between CFW and meat pH (0.19 +/- 0.07).

Development and validation of on-farm behavioural scoring systems to assess birth assistance and lamb vigour

“…lamb survival 0.03 to 0.33 (Sawalha et al, 2007;Afolayan et al, 2008) and litter size, 0.19 (Afolayan et al, 2008)) seem to be generally lower than those for performance traits (e.g. average daily gain 0.14 to 0.30 (Maxa et al, 2007), carcass fat 0.20 to 0.37 (Greeff et al, 2008) and wool 0.25 to 0.32 (Borg et al, 2009)). Heritabilities for lamb vigour behaviours (e.g.…”

Genetic parameters for wool traits, live weight, and ultrasound carcass traits in Merino sheep1

“…The other major study of Merinos from research flocks found low negative genetic correlations for yCFW with yFAT (−0.17 ± 0.07) and yEMD adjusted for weight (−0.13 ± 0.07) and moderate positive correlations with yCUR (0.43 ± 0.12 and 0.44 ± 0.15, respectively), whereas the genetic correlations with all the other wool traits were negligible (Greeff et al, 2008). Li et al (2008) reported increased ultrasound FAT and EMD at the C site in young Merino wethers (18 mo of age) with high EBV for wool growth (and similar EBV for FD and live weight), together with increased whole body protein turnover and energy retention in wool and wool-free body tissue compared with low wool growth EBV wethers.…”

“…Other traits associated with product quality (e.g., wool staple strength, carcass fat) and disease (e.g., worm resistance, fly strike) may also be important contributors to profit. There is considerable genetic variation for the major wool and meat traits (Safari et al, 2005(Safari et al, , 2007aGreeff et al, 2008;. However, the development of effective breeding programs that combine these disparate objectives also requires accurate estimates of the genetic relationships between the various traits.…”

Growth and Body Conformation Responses of Genetically Divergent Australian Sheep to Spirulina (Arthrospira platensis) Supplementation

“…This trend is expected to continue into the foreseeable future (Martin and Phillips, 2011). About 80% of Australia's national flock remains predominantly Merinobased, a wool specialist breed, regardless of the current relatively lower economic value of wool (Greeff et al, 2008;Hatcher et al, 2010;Swan, 2010;Warner et al, 2007). Hence, to capitalise on the present high demand for prime lamb, farmers are using selective crossbreeding strategies wherein meat-type terminal sires are joined with purebred Merino ewes (Ingham et al, 2007;Kopke et al, 2008).…”