Abstract :
Breed improvement in the Dorper sheep breed is based mainly on subjective assessment
in the show ring. Information is limited about the genetic relationships between subjectively
assessed and objectively measured traits in the breed. In an effort to establish
genetic parameters as well as relationships amongst these traits, this study was conducted
using Restricted Maximum Likelihood (REML) procedures. Live weight and growth traits
were moderately to highly heritable ranging from 0.18 ± 0.04 for post weaning weight
to 0.54 ± 0.15 for yearling weight using single-trait analyses. However, when multi-trait
analyses were implemented, weaning weight and average daily gain to weaning assumed
moderate h2 of 0.30 ± 0.03 and 0.27 ± 0.03 respectively. Maternal effects were significant,
although of fairly low magnitude with the exception of estimates for post weaning weight
and average daily gain to post weaning. Heritabilities of subjectively assessed traits were
fairly low, ranging from 0.07 ± 0.02 for Conformation and Type to 0.15 ± 0.03 for Size
using both single-trait and multi-trait analyses. It was established through multi-trait
analyses that subjectively assessed and objectively measured traits had mainly positive
genetic correlations. Five-trait analyses led the conclusion that there are some moderate to
high maternal genetic correlations as well as dam permanent environmental correlations
between live weight, growth, Size and Type. A few negative direct genetic correlations
were found for trait combinations of Colour with yearling weight and average daily gain to
yearling. It was concluded that despite most of the traits being positively correlated more
emphasis should be put on breed improvement basing on objectively measured traits
