5. How and when to scan ewes
For accuracy rates exceeding 98%, how ewes are handled for scanning and when ewes are scanned depends on what the ewes are being scanned for.
There have been a number of studies that have looked at the profitability of scanning, the most recent (Young, Thompson & Oldham, 2012) being readily accessible under the section "Sheep and Their Management" via the sheep CRC website http://www.sheepcrc.org.au. Many producers have also been interested in what all of the potential benefits are and how and when they are realised.
How to scan
The ALSS Group has three different handling machines, a "walk through" handler and two others. The two others put the ewes onto their backs and have each being specially designed or modified to have every ewe in exactly the "right" position for just long enough to ensure that the entire contents of the uterus of every ewe is fully examined
Sheep and wool producers put pregnant and non pregnant sheep onto their backs, their rumps and sides for, crutching, foot paring, and dagging. This is done in catching pens, on the board, in crutching cradles, in V belts, in sheep yards and in the paddock. They roll them over and around on the board for shearing and crutching then slide them down a chute.
ALSS puts sheep onto their backs to scan them because:
- All of the 6 scanning tasks can be completed with an accuracy rate of 98% plus.
- There is no need to restrict the length of joining to be 5 weeks and no more than 6 weeks.
- There is no need to stop supplements one or two days before scanning is to be done.
- There is no need to take ewes off feed and water the night before scanning.
- Fewer scanning errors arise as a result of rams being with the ewes at times “outside” the normal joining period as a result unplanned contacts between rams and ewes.
- ALSS uses both “walk through” and other handlers and because of this, understands the advantages and disadvantages of both “handling systems”
There are many reasons why a potential client of ALSS might have a preference for one handling machine over another and ALSS will respect this decision.
When to Scan
When to scan the ewes depends on what the ewes are being scanned for. With the handling machines that we use, ALSS guarantees high rates of accuracy when conducting the following scans.
- To determine pregnancy only, whenever the youngest pregnancy is 33 days and the oldest is full term. This task can be completed with any handling machine.
ALSS guarantees accuracy rates in excess of 98% for all of the following scanning tasks when ewes are scanned on their backs:
- To determine empty, single of multiple, whenever the youngest pregnancy is 35 days and the oldest is 110 days.
- To separate early from later lambing ewes, as for 2, above.
- To determine exact litter number, whenever the youngest pregnancy 35 days and the oldest is 85 days
- To separate AI and or ET pregnancies from backup pregnancies, no later than when the oldest pregnancy is 85 days
- To determine day of conception, as for 5 above.