Darren Staples / Reuters, file

In 2007, celebrity chef Gordon Ramsay called for British people to start eating horse meat, saying it was healthy and "packed with protein."

LONDON — The idea of eating horse meat has been described as the "last taboo" of English cooking.

So one of Britain's leading supermarkets, Tesco, was doubtless horrified at having to post a statement saying that horse DNA had been found in hamburgers on sale in the U.K. and Ireland.

Tim Smith, Tesco’s group technical director, said the store apologized "sincerely for any distress" caused.

"We immediately withdrew from sale all products from the supplier in question," he stressed. "The presence of illegal meat in our products is extremely serious.  Our customers have the right to expect that food they buy is produced to the highest standards."

The discovery was made by the Food Safety Authority of Ireland, which said it had carried out a study to examine the "authenticity" of several beef burger, beef meal and salami products.

The results were alarming. Ten of the 27 beef burgers tested were found to contain horse DNA, with nine containing only "very low levels."

"In one sample from Tesco, the level of horse DNA indicated that horse meat accounted for approximately 29 percent relative to the beef content," the FSAI said.

Twenty-three of the 27 burgers also tested positive for pig DNA, the FSAI said, and 21 out of 31 "beef meal products" tested were also found to contain pig DNA, but no horse DNA was discovered.

'No clear explanation'
The FSAI said that the beef burgers with horse DNA were produced at two processing plants in Ireland and one in the U.K., and were sold at Tesco and four other outlets, Dunnes Stores, Lidl, Aldi and Iceland.

Alan Reilly, the FSAI’s chief executive, said in a statement "there is no clear explanation at this time for the presence of horse DNA in products emanating from meat plants that do not use horse meat in their production process."

"In Ireland, it is not in our culture to eat horse meat and therefore, we do not expect to find it in a burger," he noted.

"Likewise, for some religious groups or people who abstain from eating pig meat, the presence of traces of pig DNA is unacceptable," he added.

Reilly stressed the products did "not pose any food safety risk and consumers should not be worried."

In 2007, celebrity chef Gordon Ramsay called for British people to start eating horse meat, saying it was healthy and "packed with protein" with a "slightly gamey" flavor, The Telegraph newspaper reported. The idea failed to take off.

In Britain, two consumers largely spoke for the nation when they told ITV News of their shock and horror.

"I'd be fuming if I found out there was horse meat in my burgers -- obviously," one man said.

"It's just not normal," a woman added. "Fine we eat cows and everything, but horse meat? No."

Jessica Stark, director of communications for World Horse Welfare, said that campaign group was concerned about horses in Europe who are driven to be slaughtered in journeys that can last several days. She said WHW did not oppose the eating of horses, but wanted to see journey times restricted to nine to 12 hours.

She said in some countries horses were seen as companions or pets and were "revered," while other nations, such as Italy and France, saw them simply as livestock.

Asked if she had eaten horse, Stark said "Gosh, no, not that I'm aware of." Asked if she would, she replied, "No I would not ... it's a personal choice."

Lee Jae-Won / Reuters

A shopper picks up Australian beef at a Lotte Mart store in Seoul, South Korea, on Wednesday. Lotte Mart was one of two major South Korean retailers to halt sales of U.S. beef.

SEOUL, South Korea -- Two major South Korean retailers suspended sales of U.S. beef Wednesday following the discovery of mad cow disease in a U.S. dairy cow. Reaction elsewhere in Asia was muted with Japan saying there's no reason to restrict imports.

South Korea's No. 2 and No. 3 supermarket chains, Home Plus and Lotte Mart, said they have "temporarily" halted sales of U.S. beef to calm worries among South Koreans.

"We stopped sales from today," said Chung Won-hun, a Lotte Mart spokesman. "Not that there were any quality issues in the meat but because consumers were worried."

South Korea is the world's fourth-largest importer of U.S. beef, buying 107,000 tons of the meat worth $563 million in 2011.

California mad cow 'just a random mutation'

The new case of mad cow disease is the first in the U.S. since 2006. It was discovered in a dairy cow in California, but health authorities said Tuesday the animal was never a threat to the nation's food supply.

Reuters reported that the first U.S. mad cow case, which was identified in 2003, caused a $3 billion drop in exports. It took until 2011 before those exports fully recovered.

Mad cow disease, or bovine spongiform encephalopathy, is fatal to cows and can cause a deadly human brain disease in people who eat tainted beef. U.S. authorities said the dead California cow has what scientists call an atypical case of BSE, meaning that a random mutation in the animal rather than infected cattle feed was the cause.

Carcass quarantined
The infected cow, the fourth ever discovered in the U.S., was found as part of an Agriculture Department surveillance program that tests about 40,000 cows a year for the disease.

USDA confirms 4th mad cow case in US

The USDA is still tracing the exact life of the infected animal, and the carcass of the cow is under quarantine and will be destroyed.

The cow was found at a rendering plant, which processes diseased or sick animals into mainly non-edible products for use in things like soap or glue.

Gosia Wozniacka / AP

The latest U.S. mad cow case is centered on the Baker Commodities transfer station in Hanford, Calif.

First discovered in Britain in 1986, the disease has killed more than 150 people and 184,000 cows globally, mainly in Britain and Europe, but strict controls have tempered its spread. The first U.S. case was found in late 2003 in an animal imported from Canada, followed by two more in 2005 and 2006. Two of those cases were also "atypical".

The news spread quickly in South Korea, which imposed a ban on U.S. beef in 2003 along with China and other countries because of mad cow disease concerns. Seoul's resumption of U.S. beef imports in 2008 sparked daily candlelight vigils and street protests for several months as many South Koreans still regarded the meat as a public health risk.

South Korea imports U.S. beef from cows less than 30 months old and there is no direct link between U.S. beef imported into South Korea and the infected animal, the country's agriculture ministry said in a statement. The infected U.S. cow was older than 30 months.

Public concern
But the ministry decided to step up inspections of U.S. beef and request detailed information on the case from the United States — initial measures to appease public concern while avoiding possible trade conflicts.

"We are still reviewing whether we will stop quarantine inspections," Chang Jae-hong, deputy director of the ministry's quarantine policy division, told The Associated Press by telephone.

Halting quarantine inspections would prevent U.S. beef from being delivered to stores as it couldn't clear customs.

At a Home Plus store in southwestern Seoul, some shoppers said they were not worried about U.S. beef as long as officials had said there were no health risks.

But others criticized the U.S. government as "arrogant" and "inconsiderate" in asserting that the discovery of an infected cow would have no impact on its meat exports.

"I won't eat meat from the countries where mad cow disease was found," said Kim Woo-sig, a self employed 47-year-old.

In Japan, officials said the country's import policy was unchanged.

'No need for change'
Japan, the world's third-largest consumer of U.S. beef and veal, restricts its imports of U.S. beef to cows of 20 months or younger.

"There is no need for change," in Japan's import rules, Chief Cabinet Secretary Osamu Fujimura told reporters.

But the latest mad cow case may jeopardize moves to expand American beef sales in Taiwan, where the government recently sparked protests by allowing sales of U.S. beef containing ractopamine, a growth additive.

Taiwan's legislature on Wednesday indefinitely postponed a planned discussion on U.S. beef imports. It is likely the government engineered the delay, fearing that the opposition would stoke sentiment against U.S. beef.

There was no immediate response from China's government. Beijing no longer has an outright ban on U.S. beef but exporters have been unable to overcome continued barriers involving inspection of the meat.

The news comes at a time of booming beef exports, with total shipments reaching a record last year thanks to expanding markets in countries like Russia and Canada, according to Commerce Department data.

But exports to Japan, Mexico and South Korea, which bought more than 80 percent of U.S. beef and veal exports in 2003, have yet to match their earlier peaks, with many of them maintaining certain restrictions that may help temper any fallout.

Mexico, which buys more U.S. beef than any other country, said it has no plans to halt imports and that it would maintain the same regimen of inspections for trade across the border.

Vietnam, which suspended U.S. beef imports between December 2003 and September 2011, also said it had not changed its policy on U.S. beef in response to the latest news.

It has also been a difficult period in the domestic market, with firms still reeling from fallout over a ground beef filler that critics called "pink slime", which was pulled from grocery store shelves and forced one producer to idle several factories and another to file for bankruptcy.

The Associated Press and Reuters contributed to this report.

Peter Dejong / AP

A ritually-slaughtered lamb is delivered at a halal butcher shop on the market in The Hague, Netherlands, Tuesday Dec. 13.

AMSTERDAM -- Political support for a proposed ban on slaughtering animals without stunning them first appeared to crumble Tuesday as the Dutch senate debated legislation that Muslim and Jewish groups say violates their religious rights.

The ban — proposed by an animal rights party and widely supported by Dutch voters — passed Parliament's lower house by a 116-30 margin in June, raising an international outcry from religious groups.

Although senators will not vote until Dec. 20, it appeared from Tuesday's debate that several parties that initially backed the ban in parliament — including the Netherlands' two largest — have changed their mind.

If the Netherlands does outlaw the slaughtering practices that make meat kosher for Jews or halal for Muslims, it will be the second country after New Zealand to do so in recent years. It would join Switzerland, the Scandinavian and Baltic countries, whose bans are mostly traceable to pre-World War II anti-Semitism.

Speaking first, Labor senator Nico Schrijver said his party now has "many questions" about the bill, including asking why it "so specifically aims its arrows at the rather small number of ritual slaughterers and why not large-scale industrial slaughter, which involves 500 million animals per year?"

"It seems to me that there may be much more effective, and less far-reaching methods that achieve the same goal" of improving animal welfare, Schrijver said, citing better education for slaughterers and better conditions in slaughterhouses.

Muslims, mostly immigrants from Turkey and Morocco, represent about a million of the 16 million Dutch population. The once-strong Jewish community numbers around 50,000 after most were deported and killed by the Nazis during World War II.

In both religions, tradition prescribes that animals' throats be cut swiftly with a razor-sharp knife while they are still conscious, so that they bleed to death quickly.

Support for the ban comes both from left-leaning voters who see this technique as inhumane, and from social conservatives who see it as foreign and barbaric.

Outside the debate, Esther Ouwehand of the tiny Party for the Animals, which proposed the ban, said it was unjust to inflict "extra suffering on animals to satisfy religious opinion."

The ban's most influential backer has been the Netherlands' anti-Islam Freedom Party.

"Do we want such practices in a civilized country as ours?" asked Freedom senator Marjolein Faber, after describing a worst-case scenario of a panicked animal taking six minutes to lose consciousness after a botched ritual slaughter.

The Royal Dutch Veterinary Association says it believes slaughtering cattle in particular while still conscious inflicts unnecessary suffering.

But Moshe Kantor, President of the European Jewish Congress, said there is "no scientific evidence" that religious slaughter, performed properly, is more painful for animals than stunning.

He said the law should be voted down in the name of freedom of religion.

"If this law is passed in a country known for its tolerant and open society, it could result in a very dangerous domino effect that could spread to other parts of Europe," he said.

Among the two parties in the Netherlands' governing coalition, the Christian Democrats opposed the ban from the beginning out of concern for the rights of religious minorities.

The pro-business VVD party, the country's largest, also now appears unlikely to support the ban.

VVD senator Sybe Schaap slammed the bill for "ethical absolutism" and said offering incentives for slaughterhouses to improve their practices would have a more positive effect than a ban.

The Dutch undersecretary for Economic Affairs Henk Blekers has said the Cabinet will only take a position on the bill after the Senate vote.