Andrew Cochrane

Lamb losses are a major component of wastage in sheep farming and can have a significant impact on farm profitability. Every year we get called by farmers concerned with their amount of ‘lamb wastage’, whether it be visible losses (abortions/deaths) or lambs that are never seen to arrive.

To begin to understand the cause of this wastage we need to first define where these losses are occurring. Lambs can be lost at any stage between conception and slaughter, but generally wastage is defined as the percentage difference between the number of lambs present at scanning vs those present at tailing. The formula for calculating your loss is as follows:

The national average is 18-20% but what you get on your farm will depend on factors such as climate, shelter, topography and scanning percentages amongst others. In general, as scanning percentages get higher we can expect that wastage will also get higher, through factors like loss of triplets.

Losses occur in two ways – directly through death of the lamb (abortion/starvation/exposure/dystocia etc) or indirectly through death of the ewe (cast/bearings/sleepy sickness/dystocia etc). Often I think people under-estimate the losses associated with a ewe, particularly when most causes of death are more common in twin and triplet bearing ewes.

If you are worried about lamb wastage, the first place to start is to begin recording all the losses you can see – both ewe and lamb – including suspected cause of death.

Once we get an idea of where the lambs are going we can make management changes to try and reduce this. Post-mortems can also be useful, especially in lambs that die during the first week of life. Information gathered from this can differentiate between some of the common causes of death and diagnose whether minerals such as iodine are lacking.

There are some general management considerations that can be used to help decrease losses, some of which need to be implemented before mating and others before lambing. These require some forethought and planning, and while this list is not exhaustive, you should consider the following:

  • Paddock selection for lambing – adequate shelter (low lying rushes/tussocks often best), slope (not too steep), dry and free from hazards (where possible)
  • Minimise periods of stress/fasting when yarding before lambing. This can help to reduce ewe losses from metabolic problems
  • Feed – as the saying goes “the best shelter for a lamb is a well-fed ewe”. Adequate feed in late pregnancy to avoid condition loss and lambing on good covers will help to ensure the ewe produces good colostrum/milk and does not need to walk far from the birth site in search of food
  • Preferential care for multiples and skinny ewes – these are the ewes and lambs that will benefit most from the aforementioned
  • Minerals – in particular iodine, selenium and vitamin E need to be considered. Iodine in particular needs attention throughout pregnancy, especially if ewes are grazing brassicas over winter
  • Disease prevention – abortion vaccines given at the correct time are a useful tool to prevent lamb losses from common causes of abortion
  • Body condition – Maintaining a ewe at body condition score 3-3.5 from mating to lambing will help to ensure the ewe is well equipped to cope with lambing and that the lamb is a good size at birth
  • Breed/genetics – Ram selection can play a significant role in survival, both breed choice and survival indexes are worth considering
  • Pre-lamb shearing – when managed well this can improve lamb survival, when managed poorly it can result in ewe deaths and therefore increased wastage.

Andrew Cochrane is a veterinarian with Northern Southland Vets.