Growing fodder for mini jerseys

Several years ago I bought an 8-tray fodder kit and still haven't assembled it. I don't have enough pasture for 2 mini-jerseys (slightly under 2/3 of an acre).   The company said I could feed 70% of their feed requirement from fodder with remaining 30% roughage.  If I had a 500-lb mini Jersey and they eat 3% of their body weight daily, that is 15 pounds.  This would equate to 2/3 of a tray of wheat or barley grass per day and not sure how much hay or grass for the remaining 30% of roughage.  Is anybody supplementing with fodder? Also, wondering about keeping her calf with her until she births again in Spring before selling or butchering.

Just looking at the figures, that 3% is DRY mass so it's going to be around 40lb of fresh fodder per day (assuming 70% water content) plus 6lb of hay (10% water content) or another 10lb of grass. Also while smaller cows eat less, they eat proportionally more per body weight than a large cow so 3% may be an underestimate. And don't forget the calf it will need to eat to. it will start on solid food at 6 weeks old at the latest.
You will need to wean the calf, which will mean keeping them separate for some time. or the strain of a half grown calf and the pregnancy will really take a toll on her.