Comparison of embryo recovery, embryo quality, oestradiol-17 beta and progesterone profiles in domestic cats (Felis catus) at natural or induced oestrus

Domestic cats experiencing a natural or FSH-induced oestrus were studied. Mated cats produced fewer (P less than 0.01) unfertilized oocytes and more (P less than 0.01) morulato blastocyst-stage embryos of better quality after a natural oestrus than after FSH treatment. Serum oestradiol-17 beta concentrations were lower (P less than 0.05) and progesterone levels rose earlier (P less than 0.05) in the induced oestrus compared to the natural oestrus group. Morula/blastocyst-stage embryos from both groups transferred to 15FSH/hCG-treated recipients produced 3 pregnancies and 2 live-born litters (1 from a natural oestrus donor and 1 from an FSH-treated donor). These results indicate that fertilization rates and embryo quality in domestic cats appear to be compromised by the FSH treatment, probably because of altered oestradiol-17 beta and progesterone concentrations.