Planting annuals for grazing, will this work?

I have 4 acres next to my subdivided permanent pasture that I planted oats and timothy last year, then grazed a couple times. Fertility is OK per the soil test. I just had lime spread at the recommended rate.

My plan this year is to first graze off what timothy comes back, in May, then plant a warm season crop for mid summer grazing. In September I will re-plant a winter crop for grazing in early spring. 

I am limited by equipment, money, and free time. My only equipment is a tractor, a light disc, and a broadcast spreader. 

My plan is to disc the ground, then heavily broadcast Sorghum-Sudan and peas or soy. I might turn loose my little boys with the fleet of garden tractors to pack it in.

 

This method worked well enough in the past to grow sunflowers, oats, and a 7 acre hay field. I have never tried it with Sorghum-Sudan or soy. I don't even know how big Sorghum Sudan seed is.

 

I will probably spread Urea when I plant, maybe again after the first grazing. I do know Nitrate poisoning is a concern if I over do it, but I don't have a grasp of what over doing it means.

 

Is there a different crop I should try instead of Sorghum-Sudan? Pearl Millet and Sudangrass are the ones I see mentioned often. I want one crop going to give me two grazings by Labor Day, planted late May. BMR Sorgham Sudan should be ready to graze in 30 days, and regrow in 30 days. I also don't want to kill my herd.

 

I am in Western PA (near Punxsutawney) and my little herd is one milk cow, 12 total beef cows and calves, and three horses. I will keep the horses off of the annual pastures. The animals are used to rotational grazing.

 

Summary: can I get an acceptable stand of Sorghun-Sudan by broadcasting and discing lightly?

 

Planting annuals for grazing, will this work?