There is almost as much cloride (salt is sodium cloride) as there is calcium in milk. Ask a dairy farmer if he ever forgot to put salt in his ration, if he did his milk production dropped 5# the next day. So if the average angus produces 20# of milk a day, not having salt will drop her production 2-3#. If calves convert milk to meat at 6 to 1 you just lost a half pound of daily gain by not putting out a salt block.