These results suggest that measurement of at least one adult expression would improve the
accuracy of selection for lifetime wool production and value. A companion paper in these
proceedings (Swan and Brown 2013) used the genetic parameters presented here and estimated the
trait and economic gains that can be achieved for various combinations of measurements across
ages and as well as incorporating genomic selection. These results confirm that recording at least
one adult assessment produced significantly greater trait and economic gain for both traits.
Furthermore genomic selection also increased the progress in both fleece weight and fibre
diameter.
Additional analysis of the breeding values of sires from these analyses shows that despite the very high correlation between traits some sires have breeding values that either increase or
decrease over time. Thus breeders with concerns about changes in fleece value across age should
be encouraged to record annual fleece value traits. The genetic evaluation for Sheep Genetics will
be modified to include annual expressions of adult fleece traits.
These were preliminary analyses, so they ignored maternal effects (genetic and environmental),
genetic group effects and the effects of previous and current physiological state which are known
to affect wool production (Hinch et al. 1996; Huisman and Brown 2009). It is likely that
accounting for these effects would further improve the correlations between traits recorded across
different ages.
There is also a general lack of recording of liveweight at adult ages in the MERINOSELECT
database. With the increasing focus on mature weight of sheep due to maintenance costs, welfare
and occupation health and safety concerns this appears to be an opportunity for breeders to record
this trait and increase the focus on this trait in the breeding program.
It is significant to note that this industry data set was/is large enough, and contains sufficient
recording of fixed effects, to support very accurate genetic parameter estimation.