The ugly U.S. winter dealt a blow to Cargill Inc.'s third-quarter profits, as unusually harsh weather caused a major trading loss in electrical power markets while slowing down grain train service in the Midwest.

To make matters worse, China's ban on certain U.S. corn imports fouled up Cargill's grain export business, also crimping quarterly earnings, which altogether were down 28 percent from a year earlier.

Minnetonka-based Cargill, one of the world's largest privately held companies, Tuesday reported net earnings of $319 million for the three months ending Feb. 28, compared with $445 million in the same period a year ago. Third-quarter revenue was $32 billion, essentially even with a year ago.

Cargill, whose holdings run from road salt to sugar trading, saw operational improvements in key businesses. However, "external events affected our quarterly results," CEO David MacLennan said in a statement.

One of those events was the coldest U.S. winter in decades, which wreaked havoc on the electricity and natural gas trading markets. MacLennan called the price spike in U.S. power markets in January "unprecedented." However, Cargill said some of its initial power trading losses were recovered through further trading.

Cargill wouldn't disclose losses on its wrong-way power bets. But an energy markets publication, SparkSpread, reported in January that Cargill lost at least $100 million in U.S. power market trading. Cargill disputes that report.

The bitter winter also hurt Cargill's U.S. grain handling business, as weather-related train service slowdowns bit into earnings. "We couldn't move grain or deliver product as fast as we wanted," said Lisa Clemens, a Cargill spokeswoman.

Midwestern farmers generally have complained about slow rail service this winter. In extreme cold, trains can't be as long as usual because the effectiveness of their air brakes is diminished. But oil trains coming from North Dakota's booming energy region also have been blamed for the train slowdown.

Cargill's overseas grain trade — and that of other grain firms — was hurt after the Chinese government banned the import of corn produced from a genetically engineered seed, Agrisure Viptera, made by agriculture giant Syngenta. Ships filled with Viptera corn and bound for China had to be rerouted, leading to extra costs for Cargill, Clemens said.

Cargill has dozens of businesses housed in four major segments, and its animal nutrition and protein segment had a strong quarter.

Earnings were up in Cargill's industrial and financial services division, with weak results in metals and energy offset by good performances in asset management and ocean shipping.

Cargill said earnings for its food ingredients and applications segment were "solid" but below a year ago. The company's origination and processing segment, also saw profits decline.