The effect of vaginal and cervical deposition of frozen-thawed semen on the fertility of sheep was tested in a field trial in which 543 Norwegian crossbred ewes aged between six months and five-and-a-half years from 10 farms were inseminated after natural oestrus. Cervical insemination with 200 x 106 spermatozoa resulted in 25-day non-return and lambing rates of 75·4 and 72·7 per cent, respectively, and vaginal insemination gave rates of 71·3 and 67·4 per cent; the cervical inseminations produced significantly higher lambing rates (P=0·04). There were significant differences between the lambing rates for different rams (P=0·006) and different farmers (P=0·003), and there was a significant interaction between farmer and deposition site (P=0·03). After vaginal insemination fertility was encouragingly high, but the results varied with the farmer, and different flock and management conditions.
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