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Four out of six steaks sampled at Wetherspoon's contained DNA from the animal, analysis showed.
millions are not being told what they are being served.
Han-u is a traditional Korean taurine–zebu hybrid breed.
Many breeds are complex mixtures of the zebu and various taurine types, and some also have yak, gaur or banteng genes. While zebu are the common cattle in much of Asia, the cattle of Japan, Korea and Mongolia are taurine (although possibly domesticated separately from the other taurine cattle originating from Europe and Africa). Other species of cattle domesticated in parts of Asia include yak, gaur, banteng and water buffalo.
The firm said there was no need to label the beef as Brazilian, adding: "Including the origin of meat on a menu is not a legal requirement."
Zebu have humps on the shoulders, large dewlaps and droopy ears. They are adapted to the harsh environment of the tropics. Adaptations include resistance to disease and tolerance of intense heat, sun, and humidity.
Three out of nine steaks sold by Greene King's Hungry Horse pub chain also tested positive for zebu, yet neither company identified the meat's origin on its menus.
It said: "JD Wetherspoon sell in excess of 140,000 steaks a week and the style and quality of this meat has been developed in conjunction with our customers to their satisfaction."
Archaeological evidence including pictures on pottery and rocks suggest that the species were present in Egypt around 2000BC and were thought to be imported from the near east or south. Bos indicus are believed to have first appeared in sub-Saharan Africa between 700 and 1500 and were introduced to the Horn of Africa around 1000.
Zebu cattle are thought to be derived from Asian aurochs, sometimes regarded as a subspecies, Bos primigenius namadicus Wild Asian aurochs disappeared during the time of the Indus Valley Civilisation from its range in the Indus River basin and other parts of South Asia possibly due to inter-breeding with domestic zebu and resultant fragmentation of wild populations due to loss of habitat.
The African sanga cattle breeds originated from hybridization of zebu with indigenous African humpless cattle; they include the Afrikaner, Red Fulani, Ankole-Watusi, and many other breeds of central and southern Africa. Sanga cattle can be distinguished from pure zebu by having smaller humps located farther forward on the animals.
The 'zebu steaks' were found in an investigation by the ITV1 programme-Undercover Mum. JD Wetherspoon said customers are not being misled because it does not describe the steaks as British.
The problem stems from the fact that a huge quantity of the beef sold in big-brand restaurants and staff canteens is from Brazil. It is cheap and there is no legal requirement for its origin to be labelled on the menu.
This same pattern is likely to be repeated at virtually all other major restaurant chains, which suggests
Picture: ZEBU off Guadeloupe (credit Peter Stewart) Operation Raleigh
Steaks served by some big restaurant chains have been found to come from beef cattle interbred with the zebu.
Zebu are used as draught oxen, as dairy cattle and as beef cattle, as well as for by-products such as hides, dung for fuel and manure, and bone for knife handles and the like.
Hungry Horse said it has served "millions of satisfied customers".
The company said the majority of its best- selling rump steaks are British born and bred.
It said the beef was "value for money" and was "the highest quality from recognised and traceable herds across the world".
In a survey, however, diners shown a picture of a zebu said they would not be happy eating a steak from the animal or would like the information made clear so they could make an informed choice.
In India, the zebu is considered to represent Nandi, the sacred bull of Shiva.
The quality of the meat is not highly regarded. In August 2007 the zebu was described as "notorious for its tough meat and poor eating quality" after imported steaks served in restaurants of two British pub chains tested positive for zebu genes.
The Bos indicus commonly have low production of milk. They do not produce milk until maturation later in their lives and do not produce much, giving it solely to their calves. When Bos indicus is crossed with Bos taurus, production generally increases.
The Co-op withdrew Brazilian beef from its stores last year following complaints from customers that it was tough.
The English Beef and Lamb Executive decided to exclude beef containing zebu DNA from its Quality Standard regime in April.
One steak bought at a JD Wetherspoon pub was 67 per cent zebu - from the hardy, humped cattle which originated in India and whose meat tends to be tougher than British beef.
Zebu, who can tolerate extreme heat, were imported into Brazil in the early twentieth century and crossbred with Charolais cattle, a European taurine breed. The resulting breed, 63% Charolais and 37% Zebu, is called the Canchim. It has a better meat quality than the zebu as well as better heat resistance than European cattle. The zebu breeds used were primarily Indo-Brazilian with some Nelore and Guzerat.
But a high proportion of Brazilian beef cattle have been interbred with the zebu - and there has long been a question over the eating quality of the animal's beef.