def _add_subjectAnimals_defaults(row, out_col_ndx_map):
    """
    Makes default values as necessary for the following required columns:
    * `Age Unit` - `Days`
    * `Age Event` - `Age at infection`
    """
    age_unit_ndx = out_col_ndx_map['Age Unit']
    age_unit = row[age_unit_ndx]
    if not age_unit:
        row[age_unit_ndx] = 'Days'
    age_event_ndx = out_col_ndx_map['Age Event']
    age_event = row[age_event_ndx]
    if not age_event:
        row[age_event_ndx] = 'Age at infection'
