Perhaps this is a minor point, but I think hoof rings are something to watch and take seriously.
A hoof ring
IS a change in the wall profile. Even if it is small, it means the hoof wall growth has deviated or been pulled away from the normal growth pattern. If it's very small, it was a very temporary and minor thing. But it does show that there was a loss of connection of the laminae. Now that doesn't mean every small ring or ripple is a big deal. But just because the laminae doesn't fail completely or cause rotation or sinking of the coffin bone, it is important to notice that there was inflammation going on. The laminae did start to pull away or stretch before the new growth came down more tightly behind it.
Then we can try to figure out what caused that problem, and try to prevent that issue from happening again. We want to avoid having the laminae become stretched (which is damage) or losing the tight connection with the coffin bone. In the OP's case, it was probably an illness so the hoof issues resolved when the illness did.
I tend to agree with almost everything
@loosie says. But if we are going by the appearance of those rings, then you would also look at my mare's hooves and think it was a minor problem. But her coffin bones did rotate and we are now working on reconnecting them with a tighter growth pattern.
My mare had good hoof structure to begin with, but every case is different depending on the seriousness of the cause and how acute it is, along with the initial health of the hoof. Hers ended up with quite severe lameness and the rotation. If her hooves had continued to rapidly deteriorate, she might have had to be put down.
Because of that, I don't think anymore that you can just look at the outside and tell how severely the coffin bones have been affected, because my mare's hooves look so similar to these pictured, yet hers was a serious case.
That being said, yes, even my mare's hooves are mild compared to many horses I've seen where the source of the laminitis continues on and on, the hooves grow ring after ring, and the hooves are never trimmed properly so are chronically lame.
@Hondo, I tend to believe the points in this article by Dr. Kellon about Fructans and laminitis. I've read that NSC = WSC plus starch, and that is a generally good number to look at when seeing how high the sugars are in the feed you are using.
https://drkhorsesense.wordpress.com/2015/06/22/its-time-to-put-the-fructan-theory-to-rest/
@Smilie, is it possible your alfalfa was higher in NSC, so it wasn't the fact that it was alfalfa but rather that it was a high sugar alfalfa? I don't see how alfalfa sugars could be the issue if for example you were feeding one of the alfalfas we've tested around here with only 8% NSC. Even if "more" of the sugars entered the bloodstream rapidly, you still have a very low amount.
But there are other theories, one of which is that legumes can cause hormonal imbalances. It can't be the fructans, since legumes are lower in fructans than grass hays.
Another potential theory is that excess protein can be converted to glucose causing insulin levels to rise, and possibly a common preservative sprayed on alfalfa can be converted to glucose. This is put out by Dr. Getty, so I take it with a grain of salt. I don't agree with her theories of just feeding horses free choice hay and grass even if they are massively obese, hoping they will regulate themselves eventually and lose weight.
https://www.americanfarriers.com/articles/8036-alfalfa-and-the-insulin-resistant-horse