Pickled milk is milk that has fermented for several days dropping the pH to 4 to 5, which prevents further degradation.
Adding buttermilk or normal bacteria in the milk starts the fermentation. If you have an older batch, taking several pints and adding to new waste milk can inoculate the milk. Do NOT mix pickled milk with new milk. Feed it up quickly. It does not improve with age, and hot weather adds risk.
Fermented milk is an older method of feeding calves. It is good and there are a lot of articles on how to do this, some in this website.
Mike Hutjens, Extension Dairy Specialist, University of Illinois - Illini DairyNET
Arlyn Heinrichs, Dairy Extension, Penn State University.
