I've noticed a picture of adorable pups in a galvanized tub. Probably ok because they aren't licking it. My father who is an old retired farmer told my daughter to get rid of the galvanized bucket she was using for water for her boxer. I forgot what he said was the problem--but he said use stainless steel only.
The only danger in using galvanized metal with animals is the leaching of zinc with PROLONGED use. Considering that these puppies stay in this clean and dry tub for maybe a minute or two at the most, I say the risk is extremely remote. This danger is mostly attibuted when you are watering your animals and the zinc gets leached into the water.
I bet they used stainless steel for milking. I tryed them a little but they rust way to easy. Just buy stainless steel and never worry about it again. Even the dollar stores sell 2qt pans for very little. Most of the catalogs are very reasonable.
And alot of time at shows the ventors have a better price.
Unbeknownst to me, my mother arrived via air plane with a bb gun in her suitcase for my son. He had seen it in her attic and asked if he could have it. Can you imagine what would happen today? Granny would have ended up in the brig!!!!