The Farmers’ Union of Wales said that five Brazilian rump steaks bought at a Tesco store in Carmarthen tested positive for the Zebu gene in laboratory DNA analysis.
The FUW said Zebu cattle produced beef that was “notorious for its tough meat texture and poor eating quality”.
Last month, Quality Meat Scotland said tests on imported beef from six supermarket chains in Scotland all tested positive for the Zebu gene. A Tesco spokeswoman said: “Over 90% of the fresh beef we sell in Britain comes from Britain - and in Wales the vast majority of the fresh beef we sell comes from the 2,000 Welsh farms we source from.
“However, to guarantee our customers availability of high-quality beef all year round at affordable prices, we sometimes have to source outside the UK. Where we do, we still insist on equivalent standards.”
Meanwhile, the co-operative societies confirmed that they had dropped Brazilian beef because of “mixed reactions from their customers”.