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Egg-laying chicken farm in Iowa

FILE - In this Nov. 16, 2009 file photo, chickens stand in their cages at a farm near Stuart, Iowa.  (AP Photo/Charlie Neibergall, File)

The avian flu continues to hit Brentwood-based Post Holdings, which announced Thursday that its breakfast unit Michael Foods won't be able to fulfill all its contracts to supply egg products.

Declaring "force majeure" in regards to Michael's egg business, Post said Michael Foods would discontinue certain product lines and take "appropriate pricing actions" due to the reduced egg supply and higher operating costs.

Force majeure is common contract language that releases a supplier from its commitment when unanticipated events occur.

Post also announced that a second company-owned flock in Nebraska tested positive for avian flu. On Tuesday, the company first reported the flu at a Nebraska flock.

With the recent spread, the flu has affected the egg supply equal to about 25 percent of the company's volume commitments before it declared force majeure, the company said in a press release.

The Brentwood-based food manufacturer, best known for its breakfast cereals, said it now is estimating the impact of the avian flu.

Last week, when it said 14 percent of its egg supply had been affected, Post estimated the effect of the bird flu on earnings would be about $20 million for the remainder of 2015.