Northern Ireland dairy farmers are on average getting less than half the industry's target for milk from forage, according to figures collected through business development groups.
With grass the cheapest form of feed, it's likely the figure has impacts on farm profitability.
The latest statistical review of the sector shows Northern Ireland dairy herd numbers now double their European counterparts and are around a third bigger than herds in the Republic.
At 92 cows on average, the typical herd here is now even one cow larger than the UK average.
AI Services carry out benchmarking for the department's rural development programme. Information is gathered from farmers in each of Northern Ireland's 150 groups.
The data collected showed the average cow here produced 7,733L a year but, while yields were high, milk from forage remained shockingly low.
Milk from forage
Speaking at a farm fertility event in Co. Down, Sam Campbell, chief executive of AI Services, said: "It is really challenging to say that the average farm in Northern Ireland is getting less than 1,600L from forage."
Campbell recounted the Richardsons' open days.
"I remember being up in a farm in Artana; at that time we were all looking at moving the target from 3,500L up to 4,000L milk from forage," he said.
"Since then we have lost the plot in Northern Ireland to a large extent with our cost of production.
For a litre of milk coming from grazed grass - in sterling terms - it costs 5-5.5p/L if you can graze the grass. Once you move into first cut silage that moves into the region of 10p/L.
"Once you move into second cut silages you get lighter yields, more costs; you're moving up again, up to around 15p/L or more. In fact, if you go up to thirds and fourths it can go up above that."
He added that concentrate cost around 30p for every litre of milk produced.
Milk accounts for 32% of Northern Ireland's total agricultural outputs, while feedstuffs make up 40% of total farm input costs.
Campbell said it was likely the rate of dairy expansion in the Republic would slow because of the shortage of fodder.
"It's the perfect storm because many of them have scaled up over the last few years," he said. "In fact, there's 450,000 extra cows in the Republic of Ireland now - that puts them up to 1.45 million.
"They will go up to 1.6 million but I have a notion they will take it a bit slower because of this - a winter that started in October down there."