Win Kirkpatrick

Vertebrate Pest Research Services

Forrestfield WA

5 June 2002

I’m going to show a bio-assay, which is a test for measuring the amount of 1080 in some oat baits. These are the oats that have got 1080 in them and on them - it’s a quality control test to make sure that the oats have got the right amount of 1080 in them, not too much.

I use water to get the 1080 out of the oats and put some of that water onto these paper disks. The water has the 1080 in it, and these paper discs have been dried in an oven.  Then the paper discs are put onto a plate which is called a bio-assay plate. The discs go onto the plate in a pattern and then the plate goes into an incubator overnight.

Overnight, the bacteria which is in the medium – which is all that white that you can see – bacteria grows, but where the 1080 is on the discs the bacteria can’t grow because it doesn’t like the 1080.

So, in the morning, I measure the different zones – these are called zones –where the bacteria hasn’t grown. I use these digital callipers to measure the zones, and from that measurement, after doing some calculations, I can work out how much 1080 was in that particular oat-bait sample. You might be able to see that the zones are different sizes – and the different sizes means that there was a different amount of 1080 in that particular sample.