Mad cow case could keep US beef out of Asia longer

New Zealand's meat exporters are taking a cautious approach to news of the latest suspected case of mad cow disease in the United States.

US officials announced late on Friday that they were retesting an older animal that had already been cleared for the brain-wasting disease, formally known as bovine spongiform encephalopathy.

This latest case raises the prospect that markets in Japan, Korea and Taiwan may remain closed to US beef for longer than expected.

After banning US beef after a BSE scare two years ago, negotiations were under way for the Asian markets to be reopened.

The ban has had a big upside for New Zealand exporters, who have more than doubled sales to those Asian markets.

In the US, live cattle futures tumbled 2.2 per cent on Monday, in reaction to the news that the US may have its second case of the disease.

New Zealand exporters are understood to be reluctant to rely on more bad news from the US to prolong inflated prices in Asian markets.

They are still bracing for the possibility that the US exports will resume later this year.

The cow at the centre of the latest case first tested positive last year but was later cleared by an immunohistochemistry test.

The animal will undergo final confirmation tests in a British laboratory after an arguably more accurate technology called "Western blot" test came back positive last week.

Analysts said American consumers were expected to continue eating steaks, roasts and hamburgers even if a second case was confirmed, because two cases out of the millions of cattle processed each year would not be seen as a threat.

"To me that doesn't seem like we have a systemic problem," said Todd Duvick, Banc of America food industry analyst.