Canada's wheat harvest may come in 1.8m tonnes below current US official forecasts, according to an official briefing which also highlighted pressures from weather and regulations facing livestock farmers.

"Harsher weather conditions" mean Canadian farmers may not have been able to complete the 10.3m acres of plantings that they informed Ottawa statisticians of in a survey in early June.

"The survey may therefore be more reflective of the producers' intentions rather than what they are actually able to seed and bring to harvest," Darlene Dessureault, a US attaché in Ottawa said.

The harvest would come in at 21.7m tonnes, she said, an estimate below Canada's "ambitious" official forecast of 22.1m tonnes and the US Department for Agriculture's 23.5m-tonne figure.

'Abnormally low temperatures'

The briefing comes days after the Canadian Wheat Board cut its forecast for the harvest in western Canada, blaming cool and dry weather.

And a separate, official, USDA report on Thursday highlighted that Alberta and western Saskatchewan, which typically account for one quarter of Canadian wheat production, had "not received significant rainfall since the 2008 harvest".

"In addition, the crop experienced abnormally low temperatures throughout June and in some areas temperatures plunged to freezing," the USDA said.

'Scramble' to feed animals

Ms Dessureault's report added that demand for feed wheat and barley had been supported by weather conditions so poor that the Canadian government had introduced tax exemptions to support livestock farmers in some areas.

"Too dry conditions in Alberta and Saskatchewan and too wet conditions in Manitoba [have] created poor pasture and forage conditions, requiring livestock producers to purchase more feed wheat," Ms Dessureault said.

Some farmers in western Canada had been "scrambling to feed their animals".

Meanwhile US regulations requiring country-of-origin information on food labels had increased the number of animals being fed in Canada, which has historically shifted much of its production to America for finishing.