Summer storms bring toxic weeds

01 Feb 2019

Nik Cronin, District Veterinarian

Do you have lambs grazing in paddocks that look like this?

Summer storms have seen crops of weeds emerge in bare paddocks across the district.

In this particular paddock, there is almost a pure stand of cathead, or caltrop, with some hairy panic present too. Both of these plants can be very toxic to livestock, and reports to us of significant losses in lambs are not uncommon.

In the most recent case, a local producer arrived home after a couple of days break to find a number of losses in the lambs grazing in this paddock, with a large proportion of the whole mob to be off colour - off feed with swollen heads and floppy ears.

Both cathead and hairy panic produce a toxin which can cause serious liver damage.

The damaged liver allows a build up of phylloerythrin in the blood which causes the affected sheep's skin to become sensitive to the sun - photosensitisation. Inflammation and tissue damage from sun exposure to variable degrees is seen in the non or lightly woolled parts of the sheep. This usually begins with swelling of areas including ears, eyelids, lips and nose, and affected animals will seek shade, and show signs of severe irritation, restlessness, rubbing and shaking of head and ears.

These early skin changes may progress to dead and sloughing skin in the affected areas.

Where damage to the liver is severe, death may result and the losses can be quite significant. In addition, it will take a period of time for an affected sheep's liver to return to health, causing delays in finishing for market.

So beware of allowing young sheep access to paddocks where cathead plants predominate!

If you have concerns around livestock health, contact your Local Land Services District Vet.