Steve,
Don't know protein of your hay, but possibly could be a little short on protein on the lightweights. lighter cattle require a higher % protein than the yearlings.
I have been supplementing dry, stockpile bermuda pasture with a 50/50 blend of corn gluten/soy hulls. this blend is about 16% protein. DDG/corn or DDG/soy hulls would also be good. According to Jim Gerrish, in his book "Management Intensive Grazing" grain fed at over .3% of body weight may depress total dry matter intake and lower the digestive efficiency of forage fiber. for this reason soy hulls could be preferable. However the current looooow price of corn is a factor. Looks like you could feed about 1lb of corn to the 350's along with 3-4lb of CG or DDG + hay.
When I am in the pasture, I do "poop patrols", observing the consistency of the manure. The ideal consistency for weight gain is similar to pancake batter. Not to runny but not stacking up. Stacking manure indicates low protein and digestiblity(dry mature grass), whereas runny indicates excess protein and high digestibility (spring grass).
Corn gluten or DDG are usually very cost effective supplement and supply extra protein, energy and fiber. They should work well with most forages.
Just my 2 cents worth.
Best wishes to you and yours.
Brock
