The existence of a red heifer that conforms with all of the rigid requirements imposed by halakha is a biological anomaly. The animal must be entirely of one color, and there is a series of tests listed by the rabbis to ensure this; for instance, the hair of the cow must be absolutely straight (to ensure that the cow had not previously been yoked, as this is a disqualifier). According to Jewish tradition, only nine red heifers were actually slaughtered in the period extending from Moses to the destruction of the Second Temple.
Because the state of ritual purity obtained through the ashes of a red heifer is a necessary prerequisite for participating in Temple service, efforts have been made in modern times by Jews wishing for biblical ritual purity and in anticipation of the building of the Third Temple to locate a red heifer and recreate the ritual. However, multiple candidates have been disqualified.
Red heifer in Alpha and OmegaEdit
The Reconstruction Alliance of Israel had heard of the birth of a red heifer in the U.S. state of Arkansas. They investigated Bill Henderson's farm, determining it was never an Indian burial ground and so not ritually polluted. After a thorough investigation, they sent Yitzhak Avigad to examine the animal. He determined Rosie was completely red, without any white patches and so agreed to buy the cow.