Last update: November 19, 2010 11:24:32 AM E-mail Print

 

Correlations of subjectively assessed traits of fine wool Merino sheep

with production and reproduction traits

 

W.J. Olivier1, J.J. Olivier2 and A.C. Greyling3

 

1Grootfontein ADI, P/Bag X529, Middelburg, E.C., 5900

2ARC:LBD (Animal Production), P/Bag X5013, Stellenbosch, 7599

3Cradock Experimental Station, PO Box 284, Cradock,5880

Corresponding author:  Willem Olivier

 


The subjective assessment of fleece and conformation traits is an integral part of the selection of replacement animals in the small stock industry. In some instances it is the only selection criteria that are used by both mutton and wool producers, although most of these traits cannot be considered as economically important. However, some traits such as wool quality and body conformation either have a direct or indirect effect on the economic viability of a farm. The purpose of this study was therefore to quantify the relationships among the subjectively assessed traits, as well as between the more important subjective traits and production and reproduction traits. Data recorded from 1988 to 2004 in the Cradock fine wool Merino stud were used for this study. The subjectively assessed traits analysed included wool quality (QUAL), variation over the fleece (VAR), wool yolk, staple formation (STAP), bellies and points (B&P), head, colour, pasterns, hocks, conformation of the front quarter (FQRT) and overall body conformation (CONF). The heritabilities of QUAL, VAR, STAP, FQRT and CONF were 0.50±0.04, 0.34±0.03, 0.40±0.03, 0.51±0.03 and 0.55±0.03 respectively. Genetic correlations (rG) obtained between body weight and FQRT and CONF were 0.67±0.04 and 0.81±0.03 respectively and the respective rG of FQRT and CONF with total weight of lamb weaned (TWW) were 0.34±0.16 and 0.35±0.15. Genetic correlations of 0.40 ±0.06, -0.47±0.05, 0.31±0.06 and -0.55±0.07 were obtained between QUAL and clean fleece weight (CFW), mean fibre diameter (MFD), staple length (STPL) and coefficient of variation (CV) respectively. The respective rG between these wool traits and STAP were 0.57±0.06, 0.63±0.05, 0.02±0.07 and 0.50±0.09. The rG of VAR with CFW and CV were -0.14±0.07 and -0.58±0.08 respectively. It is evident from the results of this study that an increase in FQRT and CONF would result in higher body weights and lifetime reproduction. Furthermore, the rG between QUAL and MFD and CV indicates that good quality wool tends to be finer with a narrower CV, thinner staples (-0.46±0.06), as well as less variation over the fleece (0.43±0.06). It is important to note that the estimated genetic correlations indicated that most of the relationships between the traits are favourable.