Successful Low Dose Insemination of Flow Cytometrically Sorted Ram Spermatozoa in Sheep
2007
de Graaf, SP | Evans, G. | Maxwell, WMC | Downing, JA | O'Brien, JK
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 x 10⁶, 5 x 10⁶ or 15 x 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 x 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.
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