A British art collector who paid $2.5 million for a postmodern, 10-by-6½- foot painting of a portrait-gazing cow says the Madison Avenue gallery’s bill of sale was a load of bull.

Robert Wylde is suing the Gagosian Gallery for more than $6 million, saying it arranged his 2009 purchase of Mark Tansey’s “The Innocent Eye Test” despite knowing that it had been bequeathed to the Metropolitan Museum of Art.