Genetic progress in the T13 Merino breeding program

The Towards 13 Micron (T13) breeding program was established by a consortium involving CSIRO Livestock Industries together with six ram breeders, with the objective of developing an ultrafine Merino flock capable of consistently producing wool at the finest end of the national wool clip. From the first mating in 1998, the flock has been selected on a high micron premium breeding objective (currently 30%). Between 1998 and 2003, the cumulative gain in the aggregate genotype of the breeding objective was approximately $40/ewe/year. The largest contribution to this improvement came from fibre diameter, which has been reduced by 2 microns. After an initial increase in clean fleece weight principally brought about by the capture of between bloodline genetic differences in the foundation animals, clean fleece weight has reduced at the rate of 1.7% per year in yearlings, and 1.1% per year in adults.