@kriita,
Feeding dairy cattle is one of the most problematic issues,we started as most folks do,just fence-up and get the cows,hoping all else will follow,but that is the most difficult approach ... what you are doing is the best approach; careful and deliberate planning.
We buy hay,get feed from brewaries,whatever you can,at times,it may even make sense to maintain fields at your local elementary school (you seed it first,kids will be happy & you'll be happy),if you have a good grass cutter,domestically you do the best to suppliment,hay,alfafa using cows waste & water. Im thinking of a green house albeit a simple one,but needs water,electricity and a few key impliments. The worst of times is during drought,costs go up and domestic feed yield is quite small. Good feed will cost 100-150 per day/cow.