(Corrects headline, Bulls, not stormers)

WELLINGTON, March 22 (Reuters) - New Zealand's Waikato Chiefs thumped South Africa's Bulls 43-27 in the Super 14 at Rotorua on Saturday to hand the defending champions their second successive loss.

The Chiefs overcame a slow start when they fell 10 points behind to outscore the Bulls six tries to three and secure a bonus point.

Scrumhalf Brendon Leonard scored two tries while centres Callum Bruce and Dwayne Sweeney, winger Lelia Masaga and number eight Liam Messam all crossed once each. Flyhalf Stephen Donald landed five conversions and a penalty.

The Bulls replied with three tries from centre Wynand Olivier, flanker Deon Stegmann and wing Akona Ndungane and three conversions, a penalty and a drop goal from flyhalf Derick Hougaard.

"It was a great effort," Waikato captain Mils Muliana said in a televised interview.

"We went away during the week, looked at our game and changed a few things.

"The tight five really set it up tonight for us at the back. Our set piece improved a lot on recent weeks and we showed what we can do with good set pieces."

The Bulls, who were surprisingly beaten by Queensland in Brisbane last week, led 10-0 after half an hour before Waikato suddenly came back. Continued...