Conception and lambing rates are lower in ewe lambs than in yearlings or adult ewes (Gordon, 1967; Forrest & Bichard, 1974). The causes of reproductive failure in ewe lambs, however, have not been determined. High ovum cleavage rates (80%) and low implantation rates (<40%) have been observed in Galway ewe lambs after various progestagen–PMSG treatments (J. F. Quirke, unpublished observation). It is possible that the ova produced by ewe lambs do not have the same potential for development as those from older ewes or that conditions in the reproductive tract of the ewe lamb are less favourable for survival. This report deals with the survival of cleaved ova from ewe lambs and adult ewes following transfer to the uteri of adult ewes.
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