Can I grain feed cattle to compensate for lack of pasture space? Is practical...
The cost of buying feed for livestock is one of the greatest costs in production. Here is a recent article that discusses cow herd feeding: http://u.osu.edu/beef/2019/07/24/planning-for-winter-2020-cow-herd-feeding/.
In general, I would advise someone not to exceed the number of animals that a pasture can support. I would expect a reduction on return with higher costs, though you would need to make an attempt to calculate your own projections.
An additional consideration is the quality of hay you may feed in the winter. Often, if hay quality is poor, supplemental grain may be needed to ensure adequate nutrition is provided to the animal. So, some grain feeding is often useful, but that should be a strategic approach in order to maximize the full benefit of pasture grazing.
Read the article above and explore the Ohio Beef Cattle Letter site for more discussion.