The Volts posted an enormous opening partnership and at lunch on the opening day of their Plunket Shield match against Central Districts were 96 without loss.
The visiting side went on to reach 479 for five declared.
Openers Hamish Rutherford (143) and Brad Wilson (111) shone with centuries.
The pair amassed a monster stand of 227 runs.
Neil Broom put his poor country season behind him with a fine knock of 93, and 19-year-old all-rounder Josh Finnie scored his third first-class half century.
But the wicket at Saxton Oval in Nelson has proved just as gentle for the home side, and Central got through 134 for one at stumps on day two.
Christi Viljoen gave the visitors early hope of running through the batting line-up when he nicked out opener Ben Smith for three.
The batsman stood his ground for a long time before eventually leaving.
He seemed pretty confused about the whole deal, glancing backwards and generally giving the impression he missed it by a mile.
Hay was happy to put away several full tosses from Rhys Phillips.
The leg spinner was not able to find a good length and was expensive.
His eight overs cost his side 40 runs.But spare a thought for Central’s Andrew Mathieson.
The 27-year-old medium-pacer returned none for 122 and went for a shade over five an over.
While Central has made a solid start to its reply, it trails Otago by 345 runs and still has a lot of batting to do.
● Canterbury has a firm grip on its match with Northern Districts at Hagley Oval.
The home side slumped to 60 for four but Todd Astle bludgeoned 195 from 189 deliveries to help his side recover and score 445.
Dean Brownlie replied with 104 for Northern but his side trails by 203 runs and escaping Christchurch with a draw is a long way off.
● The bowlers are dominating the fixture at Mount Maunganui.
Auckland is 65 for three in its second innings and leads Wellington by 61 runs.
Top order batsman Stephen Murdoch scored 109 to help Wellington take a slim four-run lead, after Auckland was dismissed for 269 in its first dig.
Auckland pace bowler Lockie Ferguson has picked up where he left off last season with five for 44, and veteran seamer Brent Arnel claimed four for 57 for Wellington.
