Pregnancy Scanning Ewes

Pregnancy scanning of ewes has become an important tool in managing reproductive performance in ewe flocks. It enables producers to make informed management decisions that will improve productivity and profitability of their sheep enterprise.

The benefits of scanning include the ability to identify and manage ewes according to their pregnancy status. Dry ewes can be sold, remated or stocked at higher rates. Single and multiple bearing ewes can be managed according to their nutritional requirements and it enables optimisation of pasture/feed. 

Scanning ewes gives you a reliable indicator of your potential lambing numbers, it allows you to realise where any production loss is occurring and manage accordingly. (e.g. lamb losses between scanning and marking). An increase of 10% in lambing percentage equates to a considerable increase in profits. 

Target conception rates for Merinos should be 120%, whilst crossbreds should conceive 30% more to achieve scanning percentages of at least 150%.

Ultrasound scanning of ewes is a simple process; all a producer requires is a standard race setup and two people to assist. Depending upon individual setups it is possible to achieve a throughput of up to 400 ewes per hour. 

It is recommended that scanning is done 40 days after rams have been removed (for wet/drying, and ensures all pregnancies can be detected). Best results for multiple scanning are 80-100 days from the commencement of joining. After the 100 days it is difficult to determine foetal numbers accurately due to size of foetus and increased bone density clouding the picture. 

Accuracy of scanning is important as this will determine the benefit to the producer. Factors known to affect accuracy include ewes not kept off feed the night prior (full rumen), extended joining periods, inadequate staff, fat animals and incorrect joining dates.

Considerable benefits can be gained from scanning for multiples, allowing the twin bearing ewes to be managed accordingly and supported through increased nutrition through placement on the best pasture and/or supplements and shelter belts. 

It is important to be aware that lamb survival is a major factor in reproductive efficiency. Scanning ewes is only a measurement of the potential of the ewe flock’s reproductive ability. Nutrition is possibly the most important factor in ensuring that the potential of the ewe flock is achieved.

We are seeing a large increase in producers using of electronic identification in recording pregnancy status. Benefits of utilising EID include:

  • Lifetime record of reproduction
  • Easier management/recording to cull twice dry or underperforming ewes
  • Selection of ewes that twin year on year – highest performing ewes
  • Can combine and separate ewe mobs to manage/optimise nutritional requirements at key times
  • Ease of collating and recalling records such as CS, BWT, lambing
  • Benchmarking for paddocks, genetics etc.
  • Reproduction Efficiency – kg of lamb weaned per ewe

Producers are no longer limited by the inability to know how many lambs’ ewes are carrying prior to lambing. Real time ultrasound has enabled producers to make significant advances in flock management and improve lambing and lamb survival rates.