MADISON, Wis. — Milk sales set records in 2014, but plummeting prices are forcing some dairy farmers to spill the surplus down the drain.

Already disheartened by the current glut, which is due to global factors and overproduction, dairy farmers say they worry that futures markets predict dwindling prices in 2015. Over in the dairy aisle, though, shoppers are milking savings by the gallon.

“I guess I’m sorry if I’m hurting the farmer or the middleman, but I’m certainly delighted to pay under $3 a gallon,” said Michael Kleinhenz.

Dairy farmers recognize the volatility of the industry. Less than a year ago, they struggled to meet global demand and milk prices climbed to record highs — about $25 per hundredweight.