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The fertility of ram spermatozoa that had undergone flow cytometric sorting (MoFlo® SX) and cryopreservation was assessed after low-dose insemination of synchronized Merino ewes. Oestrus was synchronized with progestagen-impregnated pessaries, PMSG and GnRH treatment. Ewes (n = 360) were inseminated with 1 × 106, 5 × 106 or 15 × 106 motile sorted frozen-thawed (S1, S5, or S15 respectively) or non-sorted frozen-thawed (C1, C5 or C15 respectively) spermatozoa from three rams. An additional group of ewes were inseminated with 50 × 106 motile non-sorted frozen-thawed spermatozoa (C50) to provide a commercial dose control. The percentage of ewes lambing after insemination was similar for C50 (24/38, 63.2%), C15 (37/54, 68.5%), S15 (38/57, 66.7%), S5 (37/56, 66.1%) and S1 (32/52, 61.5%) groups (p > 0.05), but lower for C5 (19/48, 39.6%) and C1 (19/55, 34.5%) treatments (p < 0.05). This study demonstrates sorted ram spermatozoa are equally fertile to non-sorted spermatozoa even when inseminated at 2% of the dose. Furthermore, at very low artificial insemination doses (1 or 5 million motile) the fertility of sorted ram spermatozoa is superior to non-sorted spermatozoa inseminated in equal numbers. These results have significance for the future commercialization of sex-preselection technology in sheep as a reduction in the minimum effective sperm number will allow a corresponding decrease in the associated cost per dose.