Why should I scan for multiples?
Scanning for multiples can help producers to make decisions that better address individual ewes’ requirements, rather than the mob average.
By scanning for multiples, you will be able to do the following:
- Tailor your twin- and single-bearing ewe management, considering their different energy requirements. Managing ewes using scanning data means that you can allocate lower-feed paddocks to single-bearing ewes and consider reducing mob size for twin- or triplet-bearing ewes. Targets for merinos and maternal ewes (see accompanying article) are that twin-bearing ewes should be 0.3–0.6 of a condition score higher than single-bearing ewes at lambing. This can improve lamb survival rates and minimise dystocia, by optimising the birthweight of both twin and single lambs.
- Be more flexible in poor and good seasons, by prioritising resources (feed, shelter, labour) to the different groups of ewes. In some seasons, it will provide selling (or buying) opportunities to manage the feed and cash resources you have available.
- Plan for the future with good data on the number of lamb fetuses present at scanning. Combined with your expected lamb survival rates, this can be used to estimate likely lamb marking results and therefore plan sale numbers. It also helps to identify where losses may occur in the reproductive cycle.
- Identify ewe fertility at a given time, which can be used to class groups of ewes for marketing.
Things to consider
- Running ewes based on pregnancy status can be more labour intensive, with more mobs to manage. You may also need to plan your paddocks to cope with more, but smaller, mobs of ewes. This could require investment in infrastructure (temporary fencing and water) and labour, depending on your current set-up.
- If twins are lambed in large mobs or under high stocking rates, there is increased potential for mismothering. It is important to keep this in mind if this is the only way you can manage your mobs of ewes.
- Scanning for multiples is much more useful than scanning for dry ewes only if the ewes are managed differently or the information is recorded for future use. For example, the number of fetuses can be used to estimate the number of lambs present at marking. Although this is good to do, the real benefit is from differently managing the ewes based on their pregnancy status.
- Contractors should be encouraged to ‘come clean and go clean’, in line with your farm biosecurity plan. They should also fill in your visitor log.
Using electronic identification in pregnancy scanning
Victoria currently has a number of pregnancy scanning contractors that offer individual animal recording using electronic identification (EID) technology.
You can also record pregnancy scanning results using your own EID collection equipment.
Why use EID to collect data?
- Data collection is quicker and more accurate than extra drafting or marking ewes, and a permanent record of the data is created, without the use of temporary sprays or raddles. If drafted mobs get mixed, EID records can be referred to for redrafting.
- Multiple traits can be recorded simultaneously – for example, the number of fetuses and their age (early/mid/late or 1st/2nd cycle).
- Traits that indicate reproductive performance can be recorded across the production cycle – for example, condition score at joining and pregnancy scanning, and lamb rearing results across years. This can help to identify the ewes that meet your breeding objective.
- Potential barriers to using EID for data collection
- Recording of pregnancy status can be slower if some of the ewes don’t have EID tags. If untagged animals are present, have a plan to apply tags efficiently. This will help maintain a smooth flow of sheep.
- EID equipment such as a panel reader and indicator can be expensive if used infrequently. Consider using your contractor’s equipment or borrow items if you don’t intend to use the equipment for other things. Having someone who can operate the technology present on scanning day is essential.
How to scan for success with EID
Join for no more than two cycles (35 days) to optimise scanning accuracy. Ensure that joining dates are correct, and rams have not had access to the ewes outside the joining period. If an extended joining period is necessary, rams should be removed after two cycles for 2 weeks before being re-joined.
Pregnancies in this second joining period can then be identified on a follow-up scan. At removal of rams, contact the contractor to book in scanning, so the ideal date can be identified, and the contractor’s travel costs are minimised.
Also arrange with the contractor who will supply the EID equipment, and discuss their equipment and crate set-up.
Ninety days after the rams were introduced is the optimum timing for scanning for multiples, although it can be done from day 80 through to day 100.
Shading caused by developing bones reduces the accuracy of scanning for multiples after day 100. Ensure that ewes are off feed and water for at least 4 hours before scanning and are not given any supplements (e.g. grain, hay, silage) the day before scanning.
It is important that scanners can set up in good yards, and that there are enough people to ensure a steady flow of ewes to the scanning crate.
If supplying EID equipment, ensure that it is fully charged, with spare batteries or alternative power sources available, if necessary.
Collecting EID data at pregnancy scanning
Contractors can link the EID tag and pregnancy status while the ewe is in the crate. This is the most efficient and accurate method if all ewes are electronically tagged. It is simple to collect multiple traits using this method.
Ensure that the next sheep’s EID tag is not read until the current ewe’s scanning result is recorded. Reading tags out of sequence will affect the accuracy of the records.
This can be avoided with correctly tagged animals, crate functionality and good yard design to ensure that only one sheep is in the crate at a time.
Some data collection systems can be programmed to require a linked EID tag and trait result before accepting the next tag.
Collecting EID data after pregnancy scanning
The alternative to collecting data at point of scanning is to identify scanning results via draft or visual markers (spray/raddle) and then record the traits against EID tags once pregnancy scanning is completed.
Using a gate to draft ewes into groups based on pregnancy status can be particularly useful when the contractor does not have EID capability or when a significant number of ewes to be scanned are not electronically tagged.
However, if groups are accidentally mixed in the yards before data are recorded, information collected during pregnancy scanning will be lost. It is also challenging to record fetal age unless a system of spray/raddle marks is used or ewes are drafted in many directions.
It is important when collecting data after scanning to be mindful of the ewes’ total time off feed and water and consider time and labour implications.