Progeny testing 91 high performance sires, entered by industry, has demonstrated considerable scope for selection and genetic improvement within maternal breeds. There are very large ranges in 1stX EBVs, such that choosing extreme sires would result in 1stX lambs differing by 10kg post weaning and their carcass fat by 8mm GR or 1.5 fat scores at the same carcass weight. Results from the subsequent 2ndX lambs have shown the differences in growth and fat levels are passed on to the second generation, with a range of 6kg for post weaning weight and 5mm GR or 1.0 fat score in carcasses. There is a dramatic effect of the maternal sire on lambing %, growth and carcass of lambs and wool, which all affect $ returns from the 1stX ewe. The major driver for $ returns is number of lambs slaughtered and the groups of 1stX ewes have ranged from 81 to 167% for lamb weaning percentage from adult ewes. The total returns varied by $35/ewe/year, which represents a difference of $13,125 in lifetime returns from 1stX ewe progeny per maternal sire.
The leading sires for each of the various traits are different, which highlights the need for breeders at all levels to carefully consider the traits that contribute to their enterprise and select sires accordingly. 1stX breeders can make considerable improvement by using sires with high EBVs for growth and leanness. In contrast, 2ndX breeders make the greatest gains from improvement in lambing rate with significant contributions from growth, leanness to match specifications, muscling and wool. Alternative breeding and alliance structures need to be facilitated, including contract matings, to encourage the use of superior sires and provide better information on the genetic merit of crossbred ewes.