h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I don't think that horses actually ever delivered milk and bread. They were the means of delivery; but the products themselves were delivered by the milkman and the baker (or more likely his boy).

Horses delivered useful fertiliser: in the early 1930s, when visiting my grandmother in Kingswood, Bristol, I was fascinated, when the baker's horse obliged, to see the housewives run out with shovel & bucket to claim their shares - what was opposite their front fences. The takings went straight on to their tiny front gardens, where roses grew in soil that had been there for a century or so.