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Victoria worm update - March 2014

Andrew Whale, Livestock Logic, Hamilton (a.whale@livestocklogic.com.au)

Recent Results

We are now well into Autumn and Summer treatments that were required should by now have been administered.

The following table reflects the amount of sheep that we have recommended second summer drenching for at Livestock Logic in March to date. Note some of these sheep would not have received a 1stsummer drench.

 

Class of Sheep

% Requiring Drenching

MA 2011 Drop

74%

Maidens/Hogg 2012 Drop

61%

Weaners 2013 drop

17%

 

At the time of writing (21st of March) we in the South West have not had an autumn break, although hopefully it is not too far away, timing of WEC’s after the autumn break is critical to maximise the amount of information we gain from them.

Not surprisingly the 2012 hoggets have a higher drench requirement than the older classes of stock. The reason for the lower percentage of lambs getting drenched would be that many of these lambs would have been drenched 5-6 weeks earlier, whereas most mature sheep do not get a follow up worm egg count until at least 2 months post drenching in summer.

Looking Forward

The autumn break (25-50mm rainfall) provides enough moisture to soften faeces, allowing larvae to emerge out and spread across pasture. This combined with lower temperatures and increased ground cover enables worm egg’s in faeces to complete lifecycle and become infective larvae on short pasture that sheep ingests allowing the lifecycle to be completed. It takes 14-21 days from the day a sheep ingests larvae to when it starts to defecate eggs within its faeces.

With the above in mind we can develop times post autumn break to give us a good indication of how contaminated pastures are and if sheep will be affected by worms. There is no point performing an egg count on sheep <3 weeks post autumn break as if they were given an effective 2nd summer drench then this count will be negligible.

The following are guidelines to post autumn break WEC monitoring

  • Lambs – Test 5-6 weeks post break, fortnightly thereafter
  • Hoggets – Generally as soon as lamb counts start to rise
  • Mature sheep – Again, based on when lambs start to rise

It is important to use visual appraisal of lambs from 3 weeks post autumn break as if they start to show signs of worms they may have low WEC but be suffering due to immature worms causing damage within the gut.

If lamb counts remain low 8-10 weeks post break it is worthwhile monitoring some adult mobs, but in most cases lambs will shoot up well before adults, exceptions include when they are grazing paddocks that have been very well prepared for low worm risk.

Tricia Veale, Benalla (triciav7@bigpond.com)

Here in the North East of Victoria we had only 23 mm of rain by the end of March and conditions have been very dry. Most property owners are now feeding their stock and the water levels in the dams are diminishing rapidly. So far for March there has been 20mm of rain and continuing warm conditions. This week the cool autumn change has swept in. The green pick is slowly emerging but more rain is needed.

Worm egg counts are beginning to rise, so it's best to check out what is happening on your property by getting a worm egg count done.

It's also very important to quarantine drench all newly purchased animals onto your property. This ensures that any Barber's Pole and drench resistant worms are eliminated before the animals are allowed onto your paddocks.

Barber’s Pole worms, Haemonchus contortus, are now active on quite a few properties in worm egg counts from clients in VIC and NSW. If you own a sheep property where Barber’s Pole worms are present, then we suggest that you keep an eye out for them increasing.

Haemonchus worms are blood suckers and can cause severe anaemia and deaths in sheep and goats. Female worms are very prolific egg-layers. They seed the paddock quite rapidly with thousands of eggs. These usually hatch within 4-6 days. Then the animals ingest huge numbers of the infective larvae which speedily travel to the abomasum (stomach). Here they attach themselves to the mucosal lining and start to suck blood. Haemonchus are thought to inject an anti-coagulant into the wound they have made. The host animal then actually loses more blood than the worms ingest. The host must replace this blood, particularly the lost red cells, by drawing on its limited iron reserves. When these are exhausted an iron deficiency anaemia results. This may be one of the reasons why apparently healthy-looking sheep or goats suddenly become anaemic and collapse.

On an infected property Haemonchus are likely to be prevalent in paddocks where a high worm egg count is found and possibly at a low, chronic level in the rest.

Mature cattle are not usually so severely affected by Haemonchus placei but very heavy burdens can cause death in young animals. The disease Haemonchosis is characterized by anaemia, subcutaneous oedema (swellings) and weight loss.

If you are concerned that Haemonchus may be present on your property, then you can get a Larval Culture done. Dung samples are pooled and incubated for several days to hatch the worm larvae from the eggs. Only by a microscopic examination of the larvae can the species of worms present be confirmed. This is because worm eggs look very similar to each other under the microscope.