Lt. Kevin Burns said the truck hit a large bump as it pulled up to the fast food restaurant and the trailer's rear gate swung open, allowing the cows to make a play for freedom, The Ogden (Utah) Standard-Examiner reported Wednesday.
Burns joked that the cows were fleeing McDonald's because "they didn't like their future."
"I was sitting in my truck watching it because I thought my eyes were lying," said trucker Wayne Sanders, who watched the scene from a truck stop across the street. "I don't know where they came from, but I'd say they'd have to weigh 800 pounds apiece ... and they were on a pretty good trot."
Sheriff's deputies spent two hours executing the plan they dubbed "Operation Hamburger Helper" to round up the stray cattle from a nearby lot.
The owner said the animals were destined for slaughter in Taylor, Utah, after "60 more days to fatten up."