Studies in ovine infertility in agricultural regions in Western Australia: analysis of reproductive wastage

Data on reproductive losses in 55 flocks involving 25,571 ewes in south Western Australia are presented. The important source of reproductive wastage was that associated with ewes that mated but failed to lamb. The magnitude of the loss (28-30 per cent) did not vary significantly among flocks joined at different times of the breeding season (November-March), or between maiden and older ewes. Losses from birth to tailing were only about 50 per cent of those associated with dry ewes. Failure to mate was not a major source of loss. Two methods of detecting dry ewes were assessed, the doppler technique and the use of vasectomised rams after fertile mating. The accuracy of detection was 82-88 per cent for the doppler technique and 90 per cent for the vasectomised rams. It was concluded that the use of vasectomised rams is the cheaper and more efficient technique.