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Sheep Farmers Should Mind The Energy Gap - Say SAC Vets

SAC News Release Ref. No: 10N08
Published: 05 Feb 2010

As Scotland clears up after the Festive Season freeze, shepherds must ensure their lambing flocks don’t suffer a New Year hangover. SAC vets are promoting a simple blood test that can spot feeding problems early and ensure that pregnant ewes go into 2010 well nourished.

The snow that fell over Scotland, and is still falling in some parts, has caused huge problems for many farmers, struggling in desperate conditions to feed their stock.  Inevitably the big freeze disrupted feeding for many animals, putting pregnant ewes under stress.  This is because even in normal years ewes carrying twins and triplets often struggle to meet the energy demands of developing lambs – and this hasn’t been a normal year!

When any break in feeding occurs, pregnant ewes are forced to fill the energy gap by using their own fat reserves.  This places the ewe at risk of developing twin lamb disease.  Once twin lambs disease is established, attempts at treatment are often unsuccessful.  Less than a third of ewes affected by the condition make a recovery, and even fewer going on to successfully rear lambs.  For this reason, spotting problems early is essential.

SAC Vet Graham Baird says, “The best way of identifying a developing energy gap is to run a simple blood test on a selection of ewes in the flock.  This test measures a chemical we call BOHB, which increases in the blood when ewes are underfed.” 

These blood samples are best taken around a month before lambing.  For flocks with scanning results, sample five ewes carrying twins and five with triplets.  It is important to select early-lambing sheep in average bodily condition.  It will give shepherds time to make any necessary changes to diet.  For sheep that have not been scanned shepherds should sample ten animals of average condition.

According to Graham Baird one or two cases of twin lambs disease each year may represent the “tip of an iceberg”.  “Many other ewes could be suffering from a subclinical disease energy gap, which has implications for their ability to rear lambs successfully.  It’s vital to monitor energy balance in lambing flocks to prevent twin lamb disease.”

Graham Baird recommends shepherds should discuss results with their vet who can tailor advice to their particular flock or situation and help them towards a more profitable lambing in 2010. 

For further information, please contact Graham Baird, SAC Veterinary Services.

 

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News Release Contacts

SAC Contact

Mr Graham Baird
Veterinary Centre Manager
SAC (Scottish Agricultural College) Work Perth Veterinary Centre, 5 Bertha Park View,
Perth
PH1 3FZ
TelWork 01738 629167
Fax 01738 643198

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News Release Issued By

Mr Ken Rundle
Senior Communications Officer
SAC (Scottish Agricultural College) Work SAC, King's Buildings, West Mains Road,
Edinburgh
EH9 3JG
TelWork 0131 535 4196

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Notes for Editors

Ewes have a high demand for energy (and, in particular, glucose) due to the requirements of milk production and of the developing foetus in late pregnancy.  To meet these high energy requirements, the animal can either increase the amount of energy taken in from the diet or mobilise body reserves of fat and protein.  Thus, any inadequacy in the former can quickly lead to an excessive degree of pressure on the latter. 

In sheep, problems with energy balance typically occur in late pregnancy due to the demands of the growing foetus.  This problem is particularly acute for the ewe since more than two thirds of foetal growth occurs during the last trimester.  An additional factor for the ewe is the weight and volume of the pregnant uterus within the abdomen, which is proportionately far larger than in other farm species.  This has the effect of reducing the bulk of food that the ewe is capable of consuming to less than 2% of bodyweight, far less than is required to fulfil typical energy demands.  The consequence of this is a requirement for body fat to be metabolised to fill the energy gap.  This places ewes that are on a low energy diet, in poor bodily condition to start with or that are carrying multiples foetuses at greatest risk of a significant shortfall and a developing state of pregnancy toxaemia. 

One outcome of excessive mobilisation of body reserves is the production in the liver of ketone bodies such as b-hydroxybutyrate (BOHB).  For groups of scanned sheep a target mean BOHB should be 1.0 mmol/l; with the corresponding figure being 0.8 mmol/l in flocks where scanning is not performed and litter size is therefore unknown.

Measurement of blood BOHB levels in sheep gives a more immediate assessment of energy balance.  As this is a flock-based measure, at least five animals need to be sampled from each management group and it is important to avoid any animal with obvious disease problems that might skew the results.