RESPONSE TO SELECTION ON BLUP OF BREEDING VALUES IN THE GROOTFONTEIN MERINO STUD

A study was conducted to estimate the response to selection on BLUP of breeding values for mature body weight (BW), clean fleece weight (CFW ) and mean fibre diameter (MFD) in a commercial Merino stud with a hig h culling rate on visual appraisal. The selection policy was to increa se BW, decrease MFD and maintain CFW. The observed annual trends were +0.63 kg for BW, -0.16 mu m for MFD and zero for CFW over a period of seven years. It is concluded that selection on BLUP of breeding values can lead to a marked increase in genetic progress in spite of the lim itations posed by high culling rates on visual appearance.