The Ambarvalia was a ritual to purify the fields of evil influences. It was a movable feast, but May 29 possibly became regarded as a customary date. A suovetaurilia, a procession of a pig, sheep, and ox, was led around the area involved three times and then sacrificed to the appropriate deities, possibly Ceres, Mars, and Bacchus.

Ambarvalia

Higgledy-Piggledy
One day in May was to
Lustrate the farmlands with
Victims in tow;
Farmers and families
Ambulatorily
Circled the boundaries three
Times in a row.