The milk situation here is much like your UK experience : a race to the bottom with two major supermarkets leading the charge with "$1 milk" being their home brands in one-litre packages.
Packaging tends to be one & two-litre (sometimes three-litre) PET bottles and one & two-litre waxed paper cartons. UHT is also quite popular. Back in April one of the big milk companies slashed the price paid to their producers, which didn't help things at all. Since then, there's been a campaign by shoppers to buy the non-supermarket brands and the naughty milk company has joined forces with one supermarket chain to produce a "Farmers Fund" milk, which is a regularly-priced two-litre bottle of which 40 cents per unit goes to provide produces in difficulties with grants between $5000 and $20,000.

Since 2000 the dairy industry was deregulated & now farmers can pasteurise & bottle their own milk for sale completely independently of the major milk companies & supermarkets. Just 8 days ago, the son of a former schoolmate released his farm's Jersey milk at a Farmers' Market.

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