Milk production in the five key exporting regions, the EU, US, New Zealand, Australia and Argentina is slowing down, according to AHDB Dairy.
It states that this is the first meaningful reduction for two and a half years.
New Zealand has recorded the biggest reduction, down 7.5% on September last year, according to the organisation.
Volumes did decline temporarily in late 2014/early 2015, which AHDB attributes to a number of EU countries holding production back due to quota restrictions.
As a result, the organisation has stated that those reductions were more than offset by a rapid rise in April.
Around 4 billion litres of this decrease is due to the fall in New Zealand production over the last two months, it states.
However, the organisation also states that over the same time period, the EU, US and Australia have all started to show reductions in milk volumes.
US production growth slowed down in August and September. The USDA forecast for the year remains unchanged at +1.4%.
September milk intake at Irish creameries up 16% year-on-year
September milk intake by Irish creameries and pasteurisers was up 16% year-on-year, figures from the Central Statistics Office (CSO) show.
Milk intake was estimated at 602.4m litres for September 2015.
This figure is 16% up on the 519.2m litres taken in during September 2014. So far this year, some 5326.5m litres of milk has been taken in by Irish creameries and pasteurisers.
This figure is 479.5m litres ahead of the amount of milk collected as of September 2014 (4847m litres).
Comparing the September 2015 milk produce figures with those for September 2014 shows that total milk sold for human consumption increased by 8.2% to 42.4m litres, the figures show.
The CSO figures show that Irish butter production was up 20.3% to 18,900t.
As of September 2015, 161,600t of butter has been collected, this is almost at last year’s total amount, which was 166,400t.
*AHDB applies a seasonal adjustment to milk production for the big five exporting regions to create an annual equivalent. This allows figures to be compared month-on-month, allowing trends to be spotted earlier than the more traditional rolling 12-month totals.