Ja. Hill et al., Micron blowout: heritability and genetic correlations with fibre diameter and secondary follicle diameter, AUST J AGR, 50(8), 1999, pp. 1375-1379
Calculation of micron blowout as the difference between fibre diameter reco
rds taken at different ages can produce 'biased' estimates of the heritabil
ity and genetic correlations due to a scale effect. In some instances, stan
dardisation of the fibre diameter records to a common genetic variance (i.e
. removal of the scale effect) changed the heritability and the genetic cor
relation estimates. The effect of standardisation on the heritability of mi
cron blowout was determined to a large extent by the difference in the gene
tic variance between the 2 fibre diameter measurements, whereas in the case
of the genetic correlation between micron blowout and another trait, it wa
s also dependent on the genetic correlation between the other trait and the
two fibre diameters. It is recommended that heritabilities and genetic cor
relations involving micron blowout be calculated after standardising the fi
bre diameter measurements to a common genetic variance. The practical impli
cations of the results are briefly discussed.