For every 100 calories of grain fed to cattle in industrial (meat) factory farms, the result's equivalent to ~30 calories.
Those "inefficient" fields you cite wouldn't need to be cultivated at all if we didn't pour two thirds of the food fields produce into fuelling the livestock industry. Not everywhere outright requires cultivation.
Most of the meat on your plate will come from a factory farm, for the sake of maximising efficiency of food production. The idyllic picture of animals roaming freely across pastures doesn't really map to the reality of modern affordable meat production[1].
As to your point concerning the meadows/monocultures comparison- a global food production system less wasteful than that which exists presently, in which we wouldn't be pouring mountains of perfectly edible food into fuelling meat production, would substantially reduce the area of land required for continual cultivation. Modern diets in the western world area astoundingly inefficient- even reducing the amount of meat consumed would help matters considerably[2].
[1] https://www.youtube.com/watch?v=L_vqIGTKuQE
[2] https://ourworldindata.org/agricultural-land-by-global-diets