Rabbenu Shemarya documents a tradition heard from his teacher Rabbenu Meshullam, that Rabbenu Sherira Gaon, the father of Rav Hai Gaon was responsible for initiating two important practices:

    A] he permitted cooking wine in order to drink it together with gentiles
    B] he bred herds of BP which he served at weddings [R' Chaim Kanievsky explains this was in order to promote awareness of their special qualities]

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Marit Ayin is not an issue because
  A] there were large numbers of BP
  B] they were regularly slaughtered and served at public functions.
This publicity provided much more than the Gemara's basic requirement - that a BP with a blemished foot has no Marit Ayin since people will remember it's a BP. The Rama clearly states even a tiny variation is adequate;
 [שיש בו שום דבר תמוה - רמ"א]