Blocks are a waste of money. Also, regardless of what the bag says, I would not feed mineral with salt. Feeding it with salt results in reduced consumption, and unless you have it in a feeder that allows 24/7 access out of the elements, I wouldn't do it.
I feed mineral once a week and salt whenever I feel they need it. By feeding straight mineral, the cows will consume everything they require. If you try to put out mineral the next few days afterward, 90% of the herd will not touch it. Their mineral 'hunger' needs to build up. A week allows that.
Also, in winter, feed a 2:1 mineral (double calcium amount, single phosphorus). If you feed 1:1, the cows will consume it like candy, trying satisfy their need for calcium. Consumption will be cut by over 50% if you put out 2:1 in the winter, instead of 1:1. :cowboy: