5 is actually the ideal body score, I would watch the heavier one's weight, drafts are prone to metabolic problems. I believe I've seen the alfalfa oat cubes at my local TSC, but I feed the alfalfa/timothy cubes so I don't know the exact conversion. I would just start them out slow and find what amount works for them. Stay with one weight for a while, then if they're not holding their weight like they should bump them up, if they're getting to heavy then bump them down.
Sully ~Sullivan's Fly Supply~ [17.1 TB] RIP 2/24/14
Rio ~Camperio~ [18.0 Oldenburg]