Thursday, 16 December 2010

Lambs and Corkscrew Grass Don’t Mix

We recently experienced significant lamb losses to the extent that we engaged the veterinarian from the Lachlan Livestock Health and Pest Authority to come out and take a look. It transpired that the root cause of the losses was our decision (made in hindsight out of ignorance and inexperience) to put the ewes and lambs post shearing of the ewes into paddocks that had a heavy load of Corkscrew Grass seed. The deciding factors at the time were that the paddocks had not been grazed for quite some time, were next in the grazing rotation plan, contained a solid stand of fresh diverse pasture which would give good nutrition, and we were keen to reduce the herbage mass to reduce fire risk.

With the benefit of hindsight what follows are the key factors that contributed to the lambs losses (no ewes were lost):

  • The Corkscrew Grass seeds penetrated the wool and skin of both the ewes and lambs
  • The resultant pain and stress on the ewes triggered many of them to wean their lambs as an automatic mechanism. Presumably being larger and older the ewes were still able to seek feed and water although many did lose condition.
  • The pain and stress on the lambs was such that many ‘hunched up’ and found it difficult to walk and feed
  • The weaning from their mother’s created a simultaneous reduction in nutrition intake for the lambs
  • The height and density of the Corkscrew Grass stand coupled with the severing of the coaching relationship with the mothers meant that the lambs either found it difficult to go to the water or were not at all able to go to the water. NB: In all of the paddocks there was a plentiful supply of good quality drinking water. There was also plenty of green feed in the paddock which will have provided for the majority of an animals hydration needs – especially given that the daily maximum ambient temperatures have not been extreme.

The veterinarian who came to our place asked the night before for us to have a couple of affected lambs close to the house – preferably one that had died a short time ago and another that was exhibiting classic symptoms of the problem. Due to the extreme wet conditions the best we could do was bring back two that were still alive but were in an advanced stage of ill-health. She took the temperature of one of the lambs and checked its mouth and eyes. This showed that the animal was not suffering from infection and had good pink colour meaning it was not anaemic. The other significant diagnostic action taken by the vet (with our permission) was to humanely slaughter one of the lambs and conduct a simple autopsy. Some of the specific attributes checked and what each indicated are:

  • Inspection of the underside of skin (visible in this photo) to see how much seed had penetrated and how far it had gone. The attached photograph shows a section of the area examined. We found it upsetting and disturbing to see what the lamb was dealing with. Seed numbers were high and in some cases they had completely penetrated, rather than just the sharp seed tip.
  • Inspection of the main lymph gland at the shoulder. This was huge in relative terms compared to what would normally be the case indicating the level of stress on the animal from the seed load
  • Inspection of the fat around the kidneys and one of the kidneys. Whilst the kidney was in excellent order there was little to no fat around it – proof that the lamb was in poor condition.
  • Inspection of the stomach and intestines. This revealed a very low level of worm infestation - nothing that would suggest parasites are causing animal losses.

Last year we had no problems with Corkscrew Grass and lambs but on the other hand seasonal conditions were dry until December. Discussions with our wool broker, shearing contractor and neighbours suggest that this year’s wet conditions really are extraordinary and ‘perfect’ for the proliferation of this species. One neighbour has also had problems with impact of Corkscrew Grass on his lambs and commented that this is the first time this has happened and that he has never experienced a season like this one.

Yesterday we had all of our lambs shorn and have drenched them for worms. This, combined with our intent to keep them on paddocks with little to no Corkscrew Grass, should reduce the risk of further losses. That said we have noticed that the seeding period for this grass now seems to be over i.e. the bulk of the plants have now ‘shed’ their seed which will make it safe for the sheep.

To the future … we will do further research on whether Corkscrew Grass can be managed better through grazing and other management techniques. It may also be time for us to look at acquiring cattle which we know are more effective at enhancing soil conditions and they naturally ‘shed’ seed like Corkscrew. What we do know with absolute certainty is that lambs and Corkscrew grass just don’t mix.

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