I see Tesco have had to withdraw an ad. from their stores, "£1 for 4 pints," as the illustration of black and white cows shows not Holstein Friesians or even British Friesians but Hereford X beef suckler cows.
I wouldn't necessarily expect their advertising staff to know the difference but that ad. must've been seen and approved by a number of other people before it was printed and distributed to their UK branches - and no-one knew any better?!
Aside from this, why do they think selling milk at below the cost of production is a good idea? Who changes their supermarket just because milk is cheaper in another one? Who buys lots of extra milk because it's cheaper this week?