TexasBred: I use the entire 1 lb bag of iodine (we usually have 10-30 head per pasture).
I ran across this and perhaps its worth some thought:
http://www.acresusa.com/toolbox/press/cattle11.htm
Pink Eye (Conjunctivitis, Ophthalmia, Sandy Blight)
Runny eyes are often the first sign of this illness, then they cloud over and look opaque. If treatment is not started promptly the eyeballs swell, ulcerate and burst — very painful and apt to cause permanent blindness.
Pink eye is caused by an organism that only operates if the host is deficient in vitamin A. It is highly contagious, but will only be caught by other animals deficient in that vitamin. In Australia, where huge areas are dry and without green feed for long periods, this can be a problem. It is made worse by the use of artificial fertilizers which inhibit all vitamins to a degree. Vitamin A is stored in the liver and there should be, in theory, enough from the wet season to see a beast through the dry, but prolonged drought and poor land may cause problems.
Geoff Wallace, the inventor of the Wallace Soil Conditioner, had a mob of Texas Longhorn bullocks that contracted pink eye on a poor paddock. Half of his farm was already converted to organic methods, so he moved the bullocks onto a healthy paddock and the pink eye cleared up in a few days. Easier than manhandling the beasts.
To treat pink eye the sufferers must be yarded as soon as possible. The affected eyes can be treated by pulling up 20 ml of cod liver oil and squirting three ml into each eye and the rest (14 ml) down the throat. This may be repeated for a few days if necessary. I am indebted to my local vet, Alan Clark, for that remedy and it certainly works.