There is no guidance that has been produced specifically for milk as it is not possible to specify in contracts "milk from Scotland" or similar. New guidance has been produced, Catering for Change - January 2011, which shows how to make full use of the flexibility available to public bodies to legally include sustainability issues in their food procurement activity.
Milk is sourced through competitive contracts awarded by public bodies. Milk companies will have full traceability of the source of milk supplied. Wisemans is by some margin the largest supplier and their labelling identifies Scottish milk but not the name of the supplying farm.