Not to hijack, but I just did the opposite, in some areas I let the grass grow all winter and into spring, left it till summer, it has all hayed off and dried, because it has been so hot and dry and because it would anyway, I am getting them to graze a lot of it now due to fire risk...
But when done like this, or even the reverse, I believe the grass can lose a lot of it's value.
I am not sure how much, and does not particularly bother me as mine just need the roughage as fed lot of other things, but has anyone tested the stages before, or is there good studies online ? I guess each variety would vary though. If it retained 50%, or 25%, that would be good to know even if a rough estimate.
We had some rain too, so now when grazed or cut the warm season grasses emerge...
To the OP, have you read up on the different ways to condition score ? I like the short ribs check if you are often close to your animals, you can monitor pretty well, can also pick up any that not doing as well as others...I also think, as others, you wont get away without giving them a lot of extra feed, that was before you said they had calves....even if they were all yearlings, you would be feeding a lot more than those acres could likely provide IMO