I didn’t say they aren’t important? You said have blood work done. You can’t determine anything about protein or AAs there. If you DO see a protein issue, that’s a disease problem, not a diet problem
It doesn’t take a nutritionist to know to feed good quality hay and the right amount of a ration balancer, or regular feed if the calories are needed, to get plenty of protein and AAs for a normal, healthy horse eating a normal amount of an average forage. Forage alone usually provides enough protein and AAs.
It’s great if someone can get hay tested. It’s often not feasible. Just know that most forages provide enough protein on their own, and what’s supplied with a feed is a bonus and “just in case”.
6% protein would be low quality grass hay. An 1100lb horse eating 22lb is getting 599gm protein from that. He needs around 700 if he’s in moderate work. Add a 30% ration balancer for another 136 and you’re covered. But grass hay averages around 10% protein, so that 22lb is 998gm. Even 8% is 799gm.