Many farmers will be having their sheep scanned around now and it is a sobering thought that 33% of lamb loss occurs between tupping and scanning.
Abortion and weak lambs are major contributors to reduced lamb numbers but early embryonic death will show as an increased number of barren ewes detected at scanning.
Contrary to popular belief, stress (handling, the weather etc) and ewe nutrition are not the only reasons for smaller than expected lamb crops.
Infection in the ewe during early pregnancy is also a cause of this problem, one of the major infections involved is toxoplasmosis.
The disease is caused by Toxoplasma gondii, which is related to the microscopic parasite that causes coccidiosis.The eggs of the parasite are picked up by the ewes from their environment in feed, forage or on pasture that has been contaminated by faeces from infected cats.
The eggs can survive for well over a year and one infected cat dropping can infect up to 100 ewes. The type of cat most likely to be infected is young or debilitated in some way.If a stable cat population is maintained on a farm the disease is less likely.
Neutering of farm cats will enable the maintenance of a stable population. If the cat population on a farm is eliminated this will act to draw in strays and increase the risk of infection.
Commonly we recognise this condition as a cause of abortion and the birth of weakly lambs with poor viability, but in early pregnancy reabsorption of the developing lamb is the result.
This year Intervet, who produce Toxovax (the only licensed Toxoplasmosis vaccine available in the UK) have introduced a scheme called Barren EweCheck. This scheme should be available through your veterinary surgeon until March 31, 2007. It involves meeting the laboratory costs of testing blood samples from barren ewes for Toxoplasmosis, the cost of taking the samples will not be covered by the scheme.
The laboratory involved can also run tests for copper, cobalt and selenium estimation at the same time but again this must be paid for. Serology for other infectious causes of early foetal reabsorption are not included in this arrangement but can be carried out at appropriate laboratories.
It is also important to remember that if toxoplasmosis is discovered on your farm it is a zoonotic disease which means that it can also affect humans, with pregnant women particularly at risk (for further information the Toxoplasmosis Trust can be contacted).
Foetal reabsorption, abortion and the birth of weakly lambs that die soon after birth can soon amount to losses of between 5% and 10% or more if ignored; whilst research suggests that anything above 2% is worth investigating.
* Iain Carrington is with Intake Vets, Hexham