In that thread about "Miracle Lubricant", I mentioned the two cattle magnets that have followed me around for thirty years. I am sure they have more than 6 lbs. of magnetic pull !!
They are oblong, weigh about two ounces, shaped like a "bolus", have HIGH power to weight ratio. You take a balling gun, insert one per animal, and they collect all the nails, rusty wire, etc that a cow vacuums up grazing, stay in the upper stomach for the lifetime of the animal to prevent "hardware diseases", weigh enough where they never pass through the animals digestive system.
These magnets look perfect, my vet supply catalog says prices run from 1.89-3.00 each, a large animal veteranarian should have them.
I'm going to test it, there is ONE light in Cullman that bugs the tar out of me !! The shape of the bolus should fit perfect on one of my basket legs.
THANKS ROSCO !! 

