Almost all of the graziers I know would never switch back to conventional feeding routines. I also think that grazed cows probably respond better to natural types of treatment, since their systems are generally in a healthy equilibrium over the long run. Fresh grasses also have biochemically active compounds that dairy nutritionists probably never take into account or analyze using standard lab techniques. These compounds help to keep the animals vigorous compared to those being constantly fed cured, stored feeds. Old-timers know that the early spring flush is loaded with health giving minerals and nutrients.
Some people advocate over-seeding pastures or boundaries with herbs known to have medicinal value.
This lets the cows nibble on them if they feel the urge. Without going into specifics, I believe there is good reason animals instinctively seek out technically non-nutritious plant materials. All this said, it is important to keep an eye on body condition so that animals don't fall into a negative energy balance, since this can hamper reproductive health as well as milk production. There certainly is a place for cured, stored feeds and that is during winter feeding. But, generally in temperate climates, many people can easily graze their animals for eight months of the year.