Silly story, because why not?:

After an unfortunate food shortage on a long winter, the Mayor was forced to resort to alternative means of stocking up supplies before they ran out. On the item list was milk – very important for growing children, and for healthy bones. But there aren’t enough cows, and the treasury isn’t good for large scale imports.

The Mayor signs an order to have each mare inspected for lactation viability and be drafted for milking. Though not a good indicator, the Mayor stipulates that mares above a certain breast size (and within fair age range) ought to be drafted.

Fluttershy then realised she was in for a busy winter.