Cow wrestler Matthew McConaughey

Matthew McConaughey was left bruised for weeks after wrestling a cow.

The 42-year-old actor trained for his role in 'Reign of Fire' - the 2002 action movie he starred in with Christian Bale - by sneaking into animal fields late at night to battle with the beasts, but admits he didn't always come out on top.

He said: ''I went out to the ranch for about six weeks on my own. It's easier at night when they're kind of asleep, standing asleep.

''I wrestled some of the calves, some of the mid-sized cows, and then there are some big boys that I just booted around with.

''I got hit in the hip - pretty much had a black-and-blue hip for weeks. It put me on my ass for sure.''

Matthew also admitted he left Christian furious after accidentally headbutting him during a scene.

He told Total Film magazine: ''That scene where we're fighting and I headbutt him? Well, it was a complete accident. But in the take, I just put it right on his forehead.

''He immediately swelled up like a frickin' tennis ball, but he kept going. I knew I'd screwed up. I looked in his eyes and I saw him go, 'Grrrrrr!' and then we kept going.

''Later he had his moment to be p***ed off at me which he absolutely deserved. There was no drama about the situation whatsoever, though he wasn't real happy about it.''