The men were heading home to Timaru from a 1970s theme stag party in Dunedin when their van collided with a bull, two cows and a calf at 12.30am.
Minutes before the accident, the men had received a call from the men in the stag party's other van, warning them about cattle wandering on State Highway 1, between Waitati and Waikouaiti.
The 55-year old driver of the van reduced his speed but was temporarily blinded when a car coming in the opposite direction flashed its lights on full.
"I guess they were trying to warn us," Mr Brown (55) said.
Moments later the van collided with the bull.
"It is a miracle no-one died," he said.
Describing the scene as "chaos", Mr Brown said he was pulled out of the wreckage by some members of the party, while emergency services worked to rescue the driver - and father of the groom - who is still recovering at Dunedin Hospital from his injuries.
Mr Brown said the accident could have been prevented, and stock should not be just shut behind a gate, but locked in.
"I run a jewellery business and everything is under lock and key. A farmer should treat his business with the same respect."
The animals were from a group of 10 which had escaped through an open gate. The farmer informed police he had closed the gate.
Recovering from a sprained left ankle, a broken toe and injuries to both his shins , Mr Brown said the men would look like "walking wounded" at the wedding in two weeks.
"We are all angry about this, but we are lucky we weren't in a car because we would have been killed if the cattle went up on the bonnet."
Tulloch Transport Dunedin area manager Peter Sutherland agreed, saying his drivers had gone two years without any incident, but had hit wandering stock on two occasions in the past two months.
"Farmers need to make sure their stock is secure," he said.
Truck drivers notified each other when they spotted unsecured stock during daylight hours, but at night wandering stock were an accident waiting to happen.
Federated farmers president Don Nicholson said unsecured stock was an issue and farmers managed the risk as best they could.
Near his own farm Mr Nicholson had encountered wandering stock from a new dairy conversion and said, "we could be seeing more of this".
"Cows just don't seem to respect fences the same way as sheep," he said.
Insurance Council of New Zealand spokesman Chris Ryan said the "general rule of thumb" for an accident involving wandering stock, was that the farmer could be held responsible if a gate was left open, or was not properly maintained.
"It is often easy to blame the farmer. But it could be people who have done it in a malicious way or people who visited the land without following the golden rule - close the gate."
