Exporters could have one million more lambs to sell than last year, but an overinflated exchange rate may mean they will be worth $400 million less than last season.
This is despite Silver Fern Farms chief executive Keith Cooper describing markets as "very buoyant".
Lambs averaged about $82 last season but companies were this year forecasting the same lamb to average less than $70, almost all due to the stronger dollar.
Meat and Wool New Zealand's Economic Service estimates 28.9 million lambs were born in spring, 1.7 million or 6.2% more than last year, after a record lambing percentage of 124%.
The service's executive director, Rob Davison, estimated 23.5 million of those would be available for export, one million more than last year, but with the exchange rate 17% higher, he said export receipts would be $400 million lower than last year.
Last year, 22.5 million export lambs earned the country $2.8 billion and Mr Davison said if the exchange rate was the same now as it was then, they would earn $2.9 billion.
Despite a 3.5% increase in numbers, he estimated this year's export lamb crop would earn $2.5 billion.
Mr Cooper said forecasting lamb numbers was difficult and he tended to view the Meat and Wool figures as providing trends.
"It's indicative and gives us a clue whether numbers are up, down or indifferent."
The figures tell him there was a heavy lambing, with good survival, but the season started more slowly than last year due to an abundance of grass.
For the week started November 9, he said the South Island kill a year ago was 194,000 compared with 159,000 this year.
The 2008 lamb crop was a 51-year low, the result of land-use change and with a low lambing percentage of just 113% due to drought.
This spring, ewe numbers were back 3.6%, but conception in autumn was high and weather kind for lambing.
The South Island lambing percentage was 129.1%, 8.5% percentage points higher than last year, giving a lamb drop of 15.8 million, 6.2% higher than last year.
Ewe numbers were back 3.8%.
The North Island lamb drop was estimated at 13.1 million, up 1.1 million on last year.
Mr Davison estimated the number of lambs available for slaughter to be one million higher at 23.5 million, a 4.4% rise on last year.
This was still 6% below the average annual export lamb crop from 2000-01 to 2007-08.
Average lamb slaughter weights were expected to fall slightly from 17.7kg last season to 17.5kg.
In Otago-Southland, the number of ewes that went to the ram in autumn was 1.7% below the previous year at 7.25 million, but the combined lambing average for the region was 128%, a 5.2% increase on 2008.
