"More and more supplementary feed is coming in through the farm gate - palm kernel and maize silage in particular," Bruce Thorrold, strategy and investment leader at DairyNZ, said.
"Secondly there has been more expansion in the South Island."
Dairy NZ data shows that in 2000-2001, about 70 per cent of farms were in the low input category - using just fertiliser and a little extra feed as inputs. The proportion of farms in that low category dropped to 32 per cent in 2012-2013.
Those in the "medium" category - bringing in 15 to 20 per cent of the total feed required - went from 17 per cent to 32 per cent over the same comparative periods.
In the high input category - with 25 to 50 per cent of required feed coming in the farm gate - went from 13 per cent in 2000-2001 to 28 per cent in 2012-2013.
Palm kernel came into its own in 2007 when a drought the North Island sent farmers scrambling for new feed sources. That year marked a step change for palm kernel as viable feed supplement. Imports of palm kernel - a byproduct of the palm oil process - have gone from 96,000 tonnes in 2003 to 1.6 million tonnes in 2013.
"Mostly supplements are allowing higher per-cow performance, so if you look at the stocking rate trend - cows per hectare - it's pretty flat whereas per-cow performance has gone up by a considerable amount," Thorrold said.
Extra feed going on to farms carries with it environmental risks. "Any time you bring more nutrients in through the gate, you increase the risk of nitrogen leaching, or phosphate run-off," Thorrold said.
But farmers with high input systems use effluent recycling systems to help offset the environmental impact.
"The average cost of production has gone up, but so have the profits," he said. "Per-cow production has gone up, mostly in the past decade - due to extra feed," Thorrold said.
Michael Brooks, executive director of the NZ Feed Manufacturers Association, said the association's members produced 171,259 of compound in 2013, up from 31,790 tonnes in 2003 for the dairy sector.
He said the compound feed business was once dominated by poultry and pigs but as of last year, dairy become the number two consumer behind the chicken meat sector.
"The days when it was just pasture are long gone," Brooks said. "There are sizeable amounts of supplementary feed now going into the dairy industry," he said.
Brooks said supplementary feed is seen as being very important - particularly in times of drought - but also in terms of the overall feed balance for dairy.