I guess what I'm really questioning is the return of annual forage-based crops as compared to perennial pastures.
I will try this question:
1) Yes, perennial pastures are often the lowest cost per pound of DM, but in most areas, they are not available 365. I know, the fescue belt is an exception.
2) So annuals are not a standalone but they can have advantages in certain situations:
- grazing earlier or later than the perennial grazing season
- providing more TDN for high input animal classes
- grazing during drought or summer slump
- grazing in moderate snow depth
3) In these situations, you need to compare the annual forage cost to the cost of grain or hay, because perennial pasture is not an option. Even if annuals are lower cost (than hay) they may still not be a good idea. You may be better off hauling animals to a sale.
4) Annuals can improve your soil fertility and reduce the cost of renovation. So you need to look at the economics of an entire rotation if you are in a lay farming system.