Last update: November 19, 2010 09:13:26 AM E-mail Print

 

Evaluation of the effect of selection for decreased fibre diameter

on production and subjective traits

 

W.J. Olivier


 Grootfontein ADI, Private Bag X529, Middelburg, E.C., 5900;

Corresponding author:  Willem Olivier

 


The increase in the demand for fine wool during the 1990’s resulted in an increase in the production of fine wool. In other words, selection for decreased fibre diameter was an important selection objective for many producers. In some instances it was even the only objective, regardless of the effect on the other production traits. The price premium that was paid for the finer wool types was in some cases the end goal of producers, as it would lead to increased profitability. It is however, important that there is a balance between the economically important traits. The purpose of this study was therefore to evaluate the effect of decreased fibre diameter on production and subjective traits. The data collected on the Grootfontein Merino stud (GM) and the Cradock fine wool Merino stud (CM) were used for this study. The decrease of fibre diameter was one of the selection objectives in both studs. The traits analysed for both studs were body weight (BW), clean fleece weight (CFW), mean fibre diameter (MFD), staple length (STPL), wool quality (QUAL), variation over the fleece (VAR), staple formation (STAP), conformation of the front quarters (FQRT) and overall body conformation (CONF). The genetic trends for MFD were y=-0.09x – 0.14 (R2 = 0.80) and y=-0.08x + 0.68 (R2 = 0.92) respectively for CM and GM. It is evident from the results of this study that there were positive trends in BW (b=0.14; R2=0.96), FQRT (b=0.13; R2=0.95) and CONF (b=0.15; R2=0.95) in CM. The same tendency was observed in GM with regard to BW (b=0.09; R2=0.86), FQRT (b=0.09; R2=0.84) and CONF (b=0.10; R2=0.84). There were also positive trends in the CM with regard to CFW (b=0.08; R2=0.80), STPL (b=0.11; R2=0.85) and QUAL (b=0.13; R2=0.96). The same tendencies were observed in GM for CFW (b=0.14; R2=0.96), STPL (b=0.14; R2=0.96) and QUAL (b=0.14; R2=0.96). It is evident from the results of this study that there was a decrease in MFD in both studs. Furthermore, there were also positive trends in all the other traits in both studs, despite the fact that there are some traits that have unfavourable genetic correlations with MFD. Thus, it can be concluded that selection for decreased fibre diameter will not have a negative effect on the other economically important traits, if the other traits are also included in the selection objectives, or monitored for any unwanted changes.