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Abstract

An evaluation of the success of MOET in two breeds of hill sheep maintained under normal systems of hill flock management.

Abstract

The success of MOET was recorded in 120 Scottish Blackface and 120 Welsh Mountain ewes, over a period of 2 years using a laparoscopic procedure for both embryo recovery and transfer. All ewes were maintained under traditional UK hill management practices. Superovulation was induced with ovine FSH, with 98-100% of ewes responding to the treatment. The overall mean superovulatory responses were 15.0±0.8 and 12.5±0.7 for Scottish Blackface and 15.3±0.9 and 12.8±0.8 for Welsh Mountain ewes in years 1 and 2, respectively. However, there was a wide degree of variation in superovulatory responses within each breed, with a range of 3 to 29 in Scottish Blackface and 1 to 40 in Welsh Mountain ewes. The mean embryo recovery rate was 71.9±3.5 and 69.6±3.4% for Scottish Blackface and 57.5±4.1 and 60.6±3.6% for Welsh Mountain ewes in years 1 and 2, respectively. The mean number of embryos recovered from Welsh Mountain ewes was lower (P<0.05) than that from Scottish Blackface ewes in both years. The lower mean number of embryos recovered in year 2 for both breeds was due to the lower superovulatory response. A significant (P<0.001) relationship was observed between superovulatory response and the number of embryos recovered for both breeds. 77 and 72% of Scottish Blackface ewes and 65 and 73% of Welsh Mountain ewes yielded ≥4 transferable embryos in years 1 and 2, respectively. Neither the mean number nor the mean percentage of transferable embryos per donor ewe differed between breeds or years. A negative relationship (P<0.001) was observed between the time of onset of oestrus and both superovulatory response and number of embryos recovered in Scottish Blackface ewes. Embryo quality was affected by the time of onset of oestrus. In both breeds, the highest proportion of grade 1 + 2 embryos and the lowest proportion of unfertilized/degenerate embryos occurred in the middle range time, with a reduction in the proportion of grade 1 + 2 embryos in ewes that came into oestrus early (<19 h) or late (>30 h) after sponge removal. One embryo was transferred to each recipient and the embryo survival rates were 76.8 and 74.6% (Scottish Blackface), and 69.6 and 87.3% (Welsh Mountain) for years 1 and 2, respectively. It is concluded that MOET is as successful in hill ewes as has been reported for lowland breeds, without making any major concessions to their hill status.