We run forage analysis as a courtesy for any customer that requests it, so I have access to the reports for several ranchers.
We don't feed alot of high protein alfalfa hay. As I have mentioned on here many times, protein is easily overfed. We feed crested wheat grass, cwg alfalfa mix, pubescent, pubescent alfalfa mix, or some barley or grain hays. Lots of people in this area don't care for brome grass for hay, but when we test it, we find it to be good.
We have found if you can mix hays, it works the best. You are right about alfalfa. It has many good qualities, it is just that range cows don't need a lot of real high protein hay. We sure like to feed some if we can, but usually not over 10# per head per day. Hay that is a grass alfalfa mix is hard to beat.
One thing that gets missed when looking at a hay or forage analysis is the ADF. That indicates the digestibility of the feed and is real important. The later the hay is harvested, the higher the ADF, the harder it is to digest. 9 times out of 10 when producers put hay out and they say their cows won't clean it up, it is due to high ADF. They simply can't digest it.
We are short of trace minerals in this country too, namely copper and zinc. That is why when we supplement a good mineral it works so well. Fills in the holes that is missed in the forage. I mention this to show you are correct in your thinking, IMO. If you add liquid feed or tubs, you are going to be adding protein and I think that could be detrimental, especially in your case where you are probably exceeding the protein requirements with what you are feeding now. No need to make this complicated or expensive when it can be dealt with simply and easily.
I will pm you and perhaps we can figure out where you are protein wise. Your feed might be way out of balance protein to energy and dry matter.
Anyway, we realize 85-90% conception rate in the first cycle is exceptionally good, but we have many customers who achieve this and have for many years.
We are in a harsh area, cows get fed a lot of 'stuff', but when we add what is missing~the whole feeding program comes together with super results.