Well, I think of it this way,
test the hay, smell the hay, if it bugs your beak the cows won't like it either, look into protein quality, over all cost of each bale with shipping to the ranch, if prices are up, look into a poorer quality available forrage and supplament with liquid protein, hay can be a great filler with good supplament
Cows are designed to eat forrage, and the microbes in their gut digest the fiber and make protein usable by the beef animal, they also utilize protein in the forrage too, so if it is not there, you need to providse it in a supplament
Cattle also require mineral supplament, loose is better, minerals are leached from hay and dry forage when it is rained on, thus quality is reduced, and some ground just is difficient in mineral content, and forrage produced on this ground will also be defficient in those minerals,
A 12-12 mineral really does not provide ballanced nutrition for a bovine, a complete loose mineral, designed to meet the needs of cattle in your area is best, local feed stores usually have a nutritionist look into regional mineral availability and have a loose miner ballanced for that area mixed and available. At least that is the way we do it here in the Brazos Valley and in Madison County, and most other regions in Texas