Animals adapt slowly to a change in diet from pasture to some other feed types i.e. from grass to lucerne or brassicas. The microbes in the rumen have to change to use the new feed and this takes time, (2-3 weeks before the animal can achieve maximum intake). Managing this transition badly can result in low or no animal growth for the period. For best results introduce animals to the diet gradually giving stock time to adjust to the new diet by allowing access to pasture and silage/hay for the first few days. Monitor animals closely as they are introduced to new feed.
To maximise animal performance avoid short periods on different feeds ie once they are introduced to the crop make sure they can stay there for a reasonable period. Hinds and calves can be introduced to a crop prior to weaning with calves then weaned back on to crop.
