In our experience it would be going from no supplemental feed to something like 2-3% body weight right off the bat. What we do is about 1-2 lbs per head initially. Don't know if that is the right thing, just what we have done. If the cows are hungry, filling them up with hay just gets their gut to working. We have found that a cow will gobble grain if she is hungry and then might get a "belly ache" so to speak then back off and wind up with acidosis and actually take a step backwards. So to me "overloading their system" is too much grain too fast; adding to the change of farm, change of water, change of everything.
Example. We just bought 10 cows, at a sale. All ckd preg except one had 1 mo calf with her. We ran them through the chute to check mouths and ear tag. Nothing else. Put them in field with 2 rolls of hay in feeders. Put some silage in trough, about 100-150 lbs since 2 are avg to a little thin and 3 are fat. We will observe them for the next several days to see how they are doing. Don't know if any/all were ever together so it will be a sorting of "pecking order" etc. Get used to the hay, the waterer, and learning the fence perimeter. Then probably in a couple days we will go take a 5 gal bucket of 17% pellets that we get and pour across the bunk and call them. It's about 20 lbs to a bucket m/l. Try to get them used to us as "good guys" with feed. We don't feed much grain, especially not to the bred cows unless they are thin; and the old "grandma group" will get a little. But I am talking about 1-2 lbs per head. We have both avg quality hay, mostly orchard grass and pasture grass, and sorghum/sudan hay that we made dry and didn't wrap since conditions were good this past fall. There are also 6 other bought cows in this field, that we got before the holidays. 2 are high headed looney tune skittish, 2 are pretty quiet older cows, 2 avg. All know the feed bunk routine now, although we have to back off to get the nutty ones to come to it. They were CHEAP, and will probably go to a sale when they have a calf on the ground. But the new ones will see what is going on, get curious and come with the others as soon as they get it figured out. Unless we get some that are very thin, they will all get the "token" amount of 1-2 lbs per head. If there are any thin ones, we will up the grain to about 3-4 lbs per head after about 2-3 weeks, and move them to a separate lot. But we try to get the condition back on them just by making sure they have enough hay to eat. During pasture season it's a little different, but they usually all get the initial come to the farm and get oriented to filling up on hay and see what their dispositions attitudes are.
We will worm only after a couple of weeks of all you can eat hay. They need to get full before you start putting the stress of even worming on them.
Don't say it is the only way to do it, just what we have kinda developed into a routine over the years. Seems to work for us. I am not opposed to grain or cubes, just that we try to have "grass genetics" and so feeding alot of grain defeats the purpose....and deflates the pocketbook!!!! But I like that if we go in a field, the cows come since they know they are going to get a "treat"....even in the summer when grass is lush...