LAUSR

Superovulation is an important step in assisted reproductive technology. Due to its short half-life, follicle stimulating hormone is usually given twice daily to ewes for three to five days, which is both timeand labour-intensive. However, dissolving follicle stimulating hormone in degradable polymers to delay absorbtion has been effective in ruminants. Experiment 1 was performed to compare a split-single follicle stimulating hormone dissolved in hyaluronan (S group; 150 mg follicle stimulating hormone on the first day and 30 mg 48 h later; n = 21) and six decreasing doses of follicle stimulating hormone (M group; 50, 50, 30, 30, 10 and 10 mg; n = 22) at 12-h intervals. Ovarian responses and numbers of recovered ova/embryos did not differ significantly between groups. However, there tended to be more Grade 1 and 2 embryos in S vs M groups (mean ± SEM, 5.1 ± 4.9 vs 2.9 ± 2.9, respectively; P = 0.08). Experiment 2 tested the effectiveness of a simplified split-single follicle stimulating hormone in purebred sheep on a commercial farm. The numbers of recovered good-grade embryos (day 2) were 4.8 ± 5.0 and 4.0 ± 2.5 per donors in Corriedale and Bond sheep breeds, respectively. We conclude that this modified technique for ewe superovulation improved animal welfare, reduced animal handling and labour and yielded results similar to or better than conventional twice-daily follicle stimulating hormone treatments.