how many times did you feed the NV raw before he had the hives; could this be a sign of detoxing?
http://www.auntjeni.com/Detoxification_Information.pdf
maybe you want to try a higher quality of raw; like primal, stella and chew's and aunt jeni's homemade raw.
maybe he's allergic to the beef; you might want to try another type of protein like turkey or rabbit.