Duncan Casey made the most of a late call-up into the starting 15 with two tries in Munster's 38-12 bonus point win over the Newport Gwent Dragons.
Argentina international Eusebio Guinazu had been due to make his Munster debut at hooker but was forced to withdraw because of a hamstring problem meaning Casey was promoted off the bench. He took full advantage of Guinazu's misfortune, scoring two second half tries and Munster ran in five unanswered scores against the struggling Welsh region.
Connacht made the most of Zebre indiscipline to finish strongly and wrap up their 43-3 bonus point win on a night with their three big New Zealand imports featured for the first time together.
All Blacks centurion Mils Muliaina mae his debut and so did Tom McCartney off the bench after half a hour, while Bundee Aki played his first home game.
Connacht dominated the opening half but had to settle for one try with a constant downpour making the going tough. However, they tacked on the points through Ian Porter for a 17-3 interval lead.
Connacht were rampant in the scrum against a weakened Zebre side who were without 13 internationals for their trip to the Sportsground, but Connacht had a lot of difficulty in the lineout.
Ireland centre Darren Cave's second try two minutes from time calmed Ulster nerves in their 25-16 win over leaders Ospreys, having nearly thrown away the match despite leading 18-3 at the break.