Autumn animal health checklist – sheep

// Pests and Diseases

Veterinarian Ginny Dodunski of Totally Vets Taumarunui provides timely sheep health and management advice with a focus on internal parasites, mating hoggets and the management of hill country ewes.

Lambs still on-farm


  • With change to cooler wetter conditions the sheep worm population changes from Barber’s Pole worm (BPW) dominant to Trichostrongylus dominant.
  • Trichostrongylus is known as the ‘Black Scour’ worm; it can cause severe scouring and even deaths towards the end of a normal drench interval when challenge is high.
  • Drenches that give persistent protection against BPW don’t have any persistency against Trichs. Don’t try to extend drench intervals to lambs yet unless they are on very clean pasture or a specialist forage.
  • Resistance issue alert – we are now seeing cases across the North Island of multi-drug resistant Trichs; including those which are quite happily surviving a triple combination drench. In some areas this has only come to light when lambs have started dying two weeks after a triple drench. CHECK your lamb drench by having a faecal egg count performed on 10 individual fresh faecal samples from lambs 10 days after you have drenched them. Do not do a bulk/composite sample for this.
  • Knock-out drench – a proven strategy for reducing the build-up of resistant worms on your farm by removing adult egg laying worms that have been quietly surviving your routine combination drench. Needs to at least be one of the novel actives (Zolvix Plus or Startect) – talk to your trusted sheep vet.
  • Unexpected lamb deaths – don’t guess, get post-mortems done.

Replacement ewe lambs

If you are going to mate these:

  • Be absolutely ruthless with your cut-off weight – you’ll get better scanning results and a better animal to go into the flock as a two-tooth, especially this year when winter feed is going to be worth gold.
  • Have a solid plan to keep feeding these to growing at 130-150g/day total LWG between mating and lambing.
  • For every 1kg gained between scanning and set stocking they are 10% less likely to be wet dry (Source: Kate Griffiths’ pHD thesis – Wastage in commercial ewe flocks).
  • It's not too late to decide not to mate these.


  • On hill country breeding farms these are the big driver of your profitability. But right now, they are probably taking the biggest hit – get some help with a feed budget if you need it and prioritise keeping some condition on these and getting feed growing for late pregnancy and lambing.
  • Ewes that start winter in BCS two or less are almost twice as likely to be dead or missing at weaning – as soon as the second cycle is over you could go into your MA ewes and identify these. What can you do to lift them even half a BCS between now and the end of May?
  • Retention of extra lambs due to inability to move off farm will create higher worm challenge to ewes in the spring. Good feed planning is a big part of the solution here as well-fed ewes can tolerate parasite challenge. But thin ewes under feed pressure may require extra help.
  • Liver Fluke is commonly more of an issue after dry autumns – April and May are a good time to check livers of cull/dog tucker ewes to assess fluke challenge.

Find out more

Ginny joins us on a B+LNZ podcast to talk about some key issues for sheep farmers in autumn at: