Understanding losses key to increasing lamb survival

Lamb post-mortems can reveal why lamb losses occur and can inform management decisions to help maximise lamb survival.
Wednesday, 22 August 2018

At the recent Central Canterbury Farming for Profit seminar at Coalgate, Stockcare vet Pete Anderson gave farmers a step-by-step description of how to carry out a basic post-mortem on dead lambs.

He says if lamb losses are above 17-18%, farmers need to understand why they are losing those lambs.

Lamb post-mortems are one of the most useful procedures vets and farmers can do as they can reveal a lot of information, including how the ewes have been managed (if they have been underfed, in poor condition, lambing date not meeting pasture growth curve etc) and whether or not they have been vaccinated.

For farmers, a basic post-mortem they can do on-farm will give an indication of whether the lamb died of dystocia, starvation/exposure, infection or iodine deficiency.

All farmers need is a sharp knife and a set of scales.     

Step-by-step guide

  1. Weigh the lamb - it should be a minimum of 4kg. Check for any abnormalities.
  2. Check the feet- has the lamb walked? If not, the feet will be covered by a thin membrane.
  3. Make an incision in the forequarter up through the neck and into the head. Check for subcutaneous oedema (fluid build-up seen as jelly like material) around the head. Check the rest of the body for subcutaneous oedema, ribcage, rump.
  4. If present, dystocia (a difficult birth) is a likely cause of death.
  5. Remove the thyroid gland; this is a butterfly-shaped gland along the front of the windpipe. It has two side-lobes connected with a bridge. This needs to be weighed by accurate scales (vet or lab) to determine whether iodine deficiency is a problem. If the thyroid weight to body weight ratio (gms/kg bodyweight) is greater than 0.4 then this suggests an iodine deficiency. The thyroids of 10 lambs are needed to get a representative sample.
  6. Cut down the foreleg to look at the foot. If oedema is present on one leg it would suggest a leg was stuck, but if all four legs are oedematous above the feet it could be a sign of exposure to extreme cold weather.
  7. Open the chest. If the lungs are pink (like marshmallow) the lamb has breathed. If in doubt cut a piece of lung and pop it in water. If it floats the lamb has breathed, if it sinks it hasn’t. Pieces of lung that float halfway suggest the lamb has taken a gasp.
  8. Look for reddish brown jelly-like fat over the heart and kidneys. This means every bit of energy has been mobilised and the lamb has run out of energy and died of starvation.
  9. Look at the stomach- is it empty or full. If it is empty this could mean the ewe has mastitis, udder problems or the ewe and lamb have been disturbed and the lamb mis-mothered.
  10. Check for signs of infections (not common in the first three days after birth) which include excessive bloody fluid in the abdomen, often with bits of fibrin material attached to different organs and abscesses which are often on the liver or in the chest. These can indicate navel infections from lambing in unhygienic conditions – e.g. on bare soil under hedgerows. 

Taking dead lambs to the vet for post mortem

Don’t put dead lambs in the deep freeze. They can be stored in a cool pace (killing shed) for up to a week. Ten lambs are a good representative sample. Take dead lambs early in the season – issues such as abortion, toxoplasmosis and campylobacter show up early. Identify what mob and paddock it came from and whether a multiple or single.