Timelapse of a friesian dairy herd strip-grazing a field in West Kerry, Ireland...

Rotational grazing is a management strategy used to maximize forage growth and encourage desirable plants and plant parts!  Generally, the leaves of plants are much more palatable, nutritious, and photosynthetically active than stems.  And, of course, some plants are much more nutritious than others.    In order to maximize forage growth, livestock are strategically moved through a series of fresh pastures in order to provide a “grazing-rest period” for plants to regrow their leaves; which in turn photosynthesize more plant tissue; which then grow at a faster rate because there is more leaf material.  After a period of significant regrowth, livestock are rotated back to the point of origin while plants are still leafy and have not begun building a lot of stem tissue.  Because livestock are more concentrated in the pasture (while other pastures are resting) the normal activity of “consuming only the most desirable plants and leaving the rest to dominate” is curtailed.