G. CAFFERY* * and C. LANGFORD** SUMMARY

joined in three successive years to Collinsville ewes and ewe progeny from all three groups were subsequently joined with Dorset Horn rams at Leeton Agricultural Research Station. When data were analysed for performance at up to five joinings and lambings, there were significant differences among the ewe groups in ovulation rate, and lambing and weaning percentages. The performance of the Booroola cross, Border Leicester cross and purebred Collinsville groups was 1.88, 1.46 and 1.24 for ovulation rate, 159, 147 and 113 for the percentage of lambs born per ewe joined, and 112, 129 and 83 for lambs weaned per ewe joined. Lamb growth and survival to weaning was highest for lambs from Border Leicester cross ewes. While average survival and growth was lower than for lambs from purebred Collinsville ewes, lambs from Booroola cross ewes were superior if adjustment was made for type of birth effects or if the performance of single or twin born lambs was compared