21 March 1997

Scans to pin

down that lambing date…

By Robert Davies

MODERN scanning machines have an in-built facility to predict stage of pregnancy by measuring the diameter of the trunk and head of lambs, though few lay scanners use it. Derek Stoakes, a partner in Ledbury-based Griffiths and Stoakes, believes this is a lost opportunity to improve the pre-lambing management of flocks.

"In any flock where ewes lamb over several weeks, it is worth scanning for stage of pregnancy so at least a couple of weeks feeding can be saved," Mr Stoakes claims. "Raddling rams is an alternative, but its an extra operation at a busy time of year, and some farmers feel crayon harnesses can harm tups chests."

The scanning service indicates more precisely how many days pregnancy has advanced. Between 30 and 45 days after conception, pregnancy can be confirmed, but the number of foetuses cannot be detected. Ewes in lamb for over 45 days can be split into groups according to predicted lambing date and number of lambs being carried. When a scanning session is booked, the farmer provides the date the tups were put in. A computer uses this to print a recording sheet for the person doing the scanning. This is used to split ewes that are 30 and 100 days pregnant into 10-day lambing periods.

A different colour is used to show stage of pregnancy, and marks are made on either the neck, back or tail to indicate the number of foetuses.

Results are entered on the record sheet. These are keyed into the practices computer, and full print outs are sent to the client, and the farms own vet.

Before the scan operator leaves the unit, lambing percentage and barren ewe percentages are calculated and presented to the farmer.

"Predicting stage of pregnancy is not 100% accurate. Any ewe tupped on one particular day can lamb over an eight-day period. Obviously there is also an accuracy factor as far as our prediction is concerned, which may be another four or five days out."

Given the variables, Mr Stoakes warns clients that predictions could be around a week out. Charge a ewe can vary as it is based on the total time involved and the number scanned.


KNOWINGLAMBINGDATE


&#8226 Improves management.

&#8226 Can save concentrate.

&#8226 Better feeding accuracy.