Looking at data from the Dairy Industry Good Animal Database (Digad), Dr Edwards compared information on twice-a-day herds with once-a-day herds to paint a bit of a picture.
''What surprised me is despite the fact we consider ourselves twice-a-day, only just over half of herds are full season twice-a-day.''
Some farmers also did a mix of once-a-day and twice-a-day, while others switched between the two during the season.
''Around 20% of the industry switch,'' Dr Edwards said.
Comparing once-a-day and twice-a-day production differences, in the first season once-a-day production decreased 11% on average.
By year four, production was back up to where it started before the switch, but was still 11% behind twice-a-day pairs taking economic implications into consideration, he said.
The impact on the level of production varied, as cows producing less than 300kg/ms tended to improve in the switch to once-a-day, while cows producing more than 300kg/ms tended to drop off.
A lot of the early advice given to farmers changing to once-a-day was to bump up cow numbers, increasing stocking rates by about 15%, Dr Edwards said,.
''In the last few years, [some would] admit that wasn't the best advice. We know that we will have to cull some cows that are not suitable for once-a-day.''
The economics behind once-a-day showed to retain profit parity with twice-a-day, farmers had to reduce costs.
Costs could be reduced through better animal health and reduced shed costs and labour and more, Dr Edwards said.
''It becomes quite unique from farm to farm.''
Once-a-day cows tended to have a tighter calving spread, while replacement rates were about the same, but removal reasons were different.
Once-a-day farmers were culling fewer empties, but more due to lower production and udder related reasons, Dr Edwards said.