I got into fodder a month ago.
After looking very hard around my small country town for seeds, all I could find was Oats at my local Rural King, even NOTHING at Tractor Supply or at other feed stores.
Oats took about 9/10 days to get to maturity. Some rabbits love the fodder and go crazy for it, but one older Doe doesn't care for it at all. So it might not work for all of them.
Know this about fodder: If you start growing fodder, you have to go all out for it. I mean, you need to set up a watering system, or you will burn out after 6 days of constant watering of all your growing fodder bins. It really gets old quickly of watering everything 3 times a day.
I simplified that ritual by using a spray bottle instead of pouring water on the bins and waiting for the water to drip out of them. It is so much faster, but still a pain.
Now lets talk about the benefits of fodder. There are not too many.
All you do is to transfer all the nutrients from inside the seed to a leaf and sprout. Loosing a little bit of nutrients in the process and gaining a lot of water mass.
But, it is my belief that the leaf and sprout is good for the rabbit digestive system.
Other than that, getting a Hay bail will be a lot easier on you.
Price of a double string Hay bail is $7 at Ace hardware, and a 50lb of Oats is $12 at Rural King.