No, you must put real values (not a zero) for ratings. Thus, only add an aggregate rating if you have one. The key fields are:
- bestRating: The highest value allowed in this rating system. If bestRating is omitted, 5 is assumed.
- ratingValue: The rating for the content.
- worstRating:The lowest value allowed in this rating system. If worstRating is omitted, 1 is assumed.
For more information on Aggregate Rating, go here.