The bonus point was a small consolation but has helped keep Otago's national championship semifinal prospects alive.
Otago is on five points with one win from three matches and will need to beat Western in Dunedin next week to remain in contention.
Waikato stunned the unbeaten North with a 49-47 win and is also on five points. Auckland Waitakere beat Western comfortably to move to nine points. It shares the top spot with North. Southland is in third place with eight points.
Otago produced an error-ridden first quarter but got back into the match through some solid defence from Louise Thayer and Hannah Broederlow, and tireless work by experienced midcourter Phillipa Finch.
Jessica Tuki also made some nice touches around the court, although her shooting statistics were not has high as she would have hoped.
"It was a strong effort but they were meaner than us, I thought," Otago coach Georgie Salter said.
"We would surge but we didn't ever look under control. We looked under stress and they were just a bit calmer than us."
With four of Otago's squad on duty with the New Zealand under-21 squad before the game, Salter expected her experienced trio of Finch, Tuki and Debbie White to step up. But White had a poor game.
The former Silver Fern threw too many loose passes and was outplayed by her former Steel team-mate, Southland centre Wendy Telfer.
White improved in the second period but Salter benched her co-captain for the crucial third period.
"I just took her off because she made too many mistakes.
"It was an instinctive decision. She just wasn't quite on her game."
Salter put Jaimee Power on at wing defence and shuffled Finch from wing defence to centre.
The home side seized the initiative with an early five-goal unanswered run and led by six at the first break.
Salter reacted by bringing on New Zealand under-21 players Camilla Lees and Broederlow at wing attack and goal defence respectively. The pair made an immediate impact. Broederlow grabbed a rebound with close to her first touch and brought some energy into the defensive circle, and Lees' introduction improved the chemistry on attack.
The changes led to Otago gaining momentum and getting its nose in front midway through the second period. Southland player-coach Natalie Avellino took advantage of an injury break to inject herself into the match.
The former Australian shooter helped stop the rot and get her side back in front.
Southland's defensive duo of Kylie Young and Te Huinga Reo Selby-Rickit kept Otago to eight goals in a tight third quarter. But with 15min remaining the match was still in the balance.
Southland's experienced trio of Young, Telfer and Avellino took control of the game and stretched the lead to eight goals. Steel shooter Julianna Naoupu also had a fine match for Southland, scoring 31 goals from 39 attempts.
Otago showed some character and made a late run to reduce the deficit to five goals.
• Southland 50 (Julianna Naoupu 31 from 39, Natalie Avellino 12/15, Kerry McKenzie 7/8), Otago 45 (Greir Campbell 30/42, Jessica Tuki 15/24). Quarter 16-10, half-time 28-26, three-quarters 38-34.
