No Colloidal Silver is not toxic cats, unless it was made improperly or the water was contaminated, or the silver impure. I've given Colloidal Silver to all of my cats, many, many times. No harmful effects, in fact the opposite. Colloidal Silver eliminated their infections. I make my own colloidal silver using .9999 pure silver wire and water that I distill myself. Before that, I used Utopia Colloidal Silver so I knew I was getting a quality product.

That poor animal was obviously given something else besides colloidal silver or it was contaminated with a toxin.

We just adopted a female cat who had a litter of kittens 2 months ago. It has been week 2 and she started bleeding from her private. She was very very tired and lifeless. I googled heavily to see what it could be. Pyometra kept up over and over again as a match to her symptoms. It's strongly suggested to take cat to a vet for emergency spay and heavy Antibiotic treatment or cat will die. I did not have the money. I gave her ,only yesterday, about 2 and a half dropperfuls of Sovereign Silver four times last night. A few hours later she was her usual self bouncing off the walls and play fighting with one of her kittens, she still has one left. We used the 10 ppm's. We have her on it still today. I read of another family cat who also cured pyometra on Silver at a similar dose 3x's a day for 3 weeks. I will be doing the same. I have been giving my own family Silver for years for many different illnesses. This stuff is safe and it is amazing. Using a reputable brand is key. Sovereign Silver is an excellent one on the market.
Peace and good health to you and yours and your critters as well.