Ovulation rates of first cross booroola compared with local breed ewes following differential feeding

The effect of at least 6 weeks of differential nutrition (high v. low plane) on live weight and ovulation rate was studied in Booroola cross ewes with (F+) and without (++) the putative Booroola gene for fecundity, and non-Booroola local breed ewes. In three experiments, significant differences (range 8–9.6 kg) in live weight at laparoscopy resulted from the differential feeding. Across genotypes, differences in ovulation rate between high and low plane ewes approached significance in Exp. 1 (2.11 vs. 1.76) and were significant in Exp. 2 (1.83 vs. 1.59) and Exp. 3 (2.68 vs. 2.20). Despite significantly higher ovulation rates in F+ Booroola cross ewes compared with ++ ewes (2.99 vs. 1.45), there was no significant interaction between nutrition and genotype; that is, both Booroola genotypes, and non-Booroola ewes exhibited similar ovulation rate responses to nutritionally induced differences in live weight.