Cold wet weather has decimated the nation's lamb "crop".
The number of lambs tailed this spring was 25.11 million head -- 2. 8 million less than last spring -- dropping 9.5 percent in the North Island and 10.4 percent in the south Island.
These drops were the biggest seen -- in terms of percentage -- between the seasons for 21 years, but agricultural economists are predicting the lamb exports may fall by less than 7 percent.
Both islands were affected by the cold and wet weather patterns that saw heavy snow fall to sea level in Southland during late September, said Beef and Lamb New Zealand economic service director, Rob Davison.
The regions worst affected were those where lambing was in full swing in late September.
"Overall, the ewe lambing percentage across the country was 109.6 percent. That's 11.9 percentage points lower than last season's 121.5 percent - the lowest percentage we've seen since the spring of 1995," said Mr Davison.
Scanning results had shown fewer pregnant ewes than last year, before the prolonged, cold wet spring hit.
The numbers of lambs from hoggets -- year-old sheep -- were up 6.2 percent on last season, partly because hoggets generally lamb later in spring and so largely avoided the bad weather. Hogget lambs this spring made up 4 percent of the total lamb crop.
Continuing cooler weather and a lack of sunshine have slowed pasture growth rates across the country, and lamb growth is trailing average of two or three weeks behind normal weights at this time of year and the early drafts are down in both numbers and average weights.
Mr Davison predicted farmers will retain fewer replacement lambs -- compared with last season -- so that their sales will generate cashflows.
"We estimate lambs for export will fall 1.4 million (down 6.8 percent) on last season, to 19.5 million," Mr Davison said. This is equivalent to half the 2.8 million fall in the overall lamb numbers.
"With fewer lambs to finish, average weights are expected to be up 1 percent on last year to 17.8 kg which would make this the highest on record," Mr Davison said.
"Farmers will draft as many lambs as possible early to take advantage of the new season lamb schedule prices, then hold off until later in the season," he said. This strategy would allow farmers to produce heavier lambs to maximise the per-head prices the animals fetched, and at the same time they would hope for a drop in the exchange rate of the New Zealand dollar late in the season.
Last season's mid-November lambs were fetched $5 to $5.20 per kilogram.
"This season, we're ahead of those levels, around $6.10 to $6.30/kg," Mr Davison said.
An active store market -- farmers buying lambs from other farmers to "finish" for later sale -- has already appeared. Driven partly by fewer lamb numbers, it has also been fired by concerns in some regions that those farms may have to cope with a summer drought brought by the current La Nina weather pattern, meaning those properties would benefit by reducing the numbers of animals they have to feed going into autumn.