Across-stud evaluation of Merinos in South Africa

A study was conducted to specify a mixed model for across-stud breeding val ue estimation for Merino sheep in South Africa regarding body weight, clean fleece weight and mean fibre diameter. A total of 24 000 records from 18 s tuds during the period 1987 to 1996 were analysed using the GLM procedure o f SAS and the DFREML program of Meyer. All three traits were significantly (P<0.01) influenced by herd-year season (hys), sex, birth status and age at measurement (fitted as a linear regressor) as well as a hys x sex interact ion. As far as the random effects are concerned, maternal effects and a hys x sire interaction seem to be important for body weight, less so for clean fleece weight and unimportant for mean fibre diameter. Genetic trends were low to non-significant. Mechanisms and methods however exist to greatly en hance genetic progress.