Ewe scanning - it's all in the timing say experts

SHEEP producers should scan ewes around the middle of their pregnancies to avoid problems and cut their overall feed bills, according to Eblex.

Ewes and lambs in the spring sunshine

SHEEP producers should scan ewes around the middle of their pregnancies to avoid problems and cut their overall feed bills, according to Eblex.

Scanned ewes can be separated according to their feeding requirements and the scanning percentage can be used as a measure of the overall health of the sheep enterprise.

The scanning percentage – worked out by the scanner or calculating the total numbers of lambs scanned and dividing it by the number of ewes put to the tup, then multiplying it by 100 – should be compared year-on-year to identify any significant changes.

Eblex livestock scientist Liz Genever said: “For example, if the scanning percentage decreased from 178 in 2011 to 175 in 2012, this would be a change of -1.7%.

“A negative shift between years of more than 5% requires investigation. It may be explained by changes to the system, ewes being in poor condition or reduced feed quality.

“It is also worth thinking about whether rams could be affected by poor fertility due to lameness or a body condition score of less than three.”

She also advised looking at the barren rate – which is calculated by dividing the number of empty ewes by the number put to the tup and multiplying this by 100.

“If the barren rate is greater than 5%, seek veterinary advice,” said Ms Genever.

“Making comparisons with results from previous years may also help identify any significant trends. The vet may suggest taking blood samples to look at whether ewes have been exposed to toxoplasmosis or enzootic abortion.

“Looking at trace element levels may provide an explanation, but this should only be explored once other possible causes have been ruled out, such as feed quality during flushing, tupping and early pregnancy, body condition and ram fertility.”

Feed composition should not be ignored, she said, because selenium deficiency or too much phosphorus can increase embryonic mortality.

“Finally, producers should give some thought to dealing with barren ewes. Generally, culling should be the only option,” said Ms Genever.

 

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