Lambing success paves the way for successful flock performance

A successful lambing will set the scene for a potentially healthy year as far as the farm’s finances are concerned.  On the other hand, losing lambs as a result of enzootic abortion (EAE) or toxoplasmosis will not only make the lambing period one to remember for the wrong reasons; it will also have a significant impact on the financial health of the farm.  With each abortion costing over £100, Rosemary Booth, large animal veterinary adviser at Intervet examines the role of vaccination.

There are a number of vaccines available to help prevent abortion in ewes caused by EAE and/or toxoplasmosis, but the number of flocks in which these vaccines are used is, and has been for many years, well below the number which would actually benefit from using the vaccines. 

One annual survey that has been running for a number of years is Intervet’s FlockCheck, a subsidised blood testing service that aims to quantify exposure to  EAE and toxoplasmosis.  Results for the last 12 years show that the number of flocks exposed to either one or both of the diseases has remained relatively constant, and at high levels. 

Graph 1. The incidence of EAE and toxoplasmosis on the UK unvaccinated sheep flock 1994-2006

The number of flocks infected with both diseases, and likely to respond to a combined vaccination policy, remains in the region of 40%.

The survey has also shown for the last five years, the abortion and barrenness rate has been between 10% - 15%.  A 10% barrenness/abortion rate in a flock of 500 ewes lambing at 150% equates to losses of 75 lambs, while at 15% this increases to 112 lambs. 

Tackling the problem

It is best to investigate the cause of any problem at lambing time, as this is when dead, stillborn and weak lambs are seen.  If this can’t be done, the next best time is within the first three months after lambing, when blood samples from affected ewes can still give an indication of the causes.  It is wrong to accept that abortion is part and parcel of the lambing season – they should be investigated and the cause, whenever possible, identified.

As a rule of thumb, where the abortion rate exceeds 2%, the causes are definitely worth further investigation as vaccination is likely to more than pay for itself in these situations. 

Bought in replacements should be regarded as suspect, since they are often cited as the source of disease.  There is no test that can confirm if a ewe is carrying EAE until she actually aborts.  The best approach is to vaccinate all replacements, irrespective of their history, since the outcome of not vaccinating may only become apparent many months later when lambing comes around. 

With the cost of vaccinating against both EAE and toxoplasmosis being in the region of £4.00 per ewe (for her lifetime - not annually), incorporating preventative measures against both diseases as part of any flock health plan can only make good sense.  Fortunately the vaccines against these diseases – Enzovax® and Toxovax® - from Intervet are uniquely licensed to be used together thereby minimising the labour required for vaccination.  Healthy sheep produce healthy lambs that finish early and make money, so keeping them in good health should be a priority.