Last Sunday I went to Tractor Supply in Marinette, WI to buy some supplies. While there, I picked up a sheep mineral block.
When I set it out, I was careful to see that the sheep had plenty of water. I knew they would overdo it on the mineral block and they'd be thirsty.
The next morning, the water supply, which I thought was more than enough, was empty, and some of the sheep were showing symptoms of salt poisoning. Though I didn't know that at first, I was too busy filling all the water troughs and making sure all the sheep got a drink.
The info on the internet was grim. Salt poisoning is 50% fatal. Or more than 50% fatal, depending on which information source you read. And there isn't much to do to treat other than give them water in small amounts throughout the day--- too much water at once can be bad.
Sure enough, I lost 2 ewes that day--- including Rilla, one of my best older Dorper cross ewes, and her purebred Shetland mother, Nadezhda. Yesterday evening, I found another ewe dead.
The good news is that my most valuable Dorper cross ewe, Sarang, recovered even though she was rather badly affected.
I've decided, as a result of this experience, that my sheep get plenty enough minerals from all the weeds they eat. They don't need mineral blocks, especially if they can cause results like this in spite of precautions.